Human evolution: the latest discoveries
Human evolution: the latest discoveries
Author: Carlos A. Marmelada.
Published in: Lecture given at the Refresher Course for academic staff "Science, Reason and Faith" organised by the Higher Institute of Religious Sciences of the University of Navarra.
Date of publication: 5 November 2005
Subjects: evolution, man, science, history of science, scientific method, scientific method.
4.6.- Our most ancient direct ancestors I. Homo sapiens idaltu.
4.8.- Our earliest direct ancestors II. The Omo Kibish skulls.
Introduction. The human being: that great mystery.
We, human beings, are the only entities in all of nature that question their origin, their evolution and their destiny, as well as the meaning of their existence. Who are we? That is to say: What does it mean to be human? Where do we come from? That is: what was the species, and genus, of pre-human hominid that gave rise to the human genus? How did our genus evolve to become us? When did our species appear? Where did it appear, and from which human species did ours emerge? What is the origin of modern human consciousness? Did it appear at the same time as modern human anatomy? Are we a lucky monkey, or are we children of God? Are we just another animal? Are we made only of subject? Or do we have a rational, spiritual soul? Does death annihilate, or nihilise, the whole human individual, or is there something of us that survives death? What is the meaning of human existence? Will humanity ever disappear?
The ability to ask questions like these and the ability to develop answers that are rational, properly argued and empirically grounded is undoubtedly one of the characteristics that sets us apart from all animals, and makes us unique in the whole of physical reality.
On the entrance of the temple of Apollo at Delphi one could read the inscription: Know thyself, nosce te ipsum. The fulfilment of this imperative has led philosophers* (1) (and theologians) to reflect on human nature for 2500 years. But what about science? What about science? What does science tell us about the origin and evolution of man? The University of Navarra has been kind enough to invite me to speak to you about this very subject topic: The current state of scientific knowledge about human evolution, with special attention to the great discoveries that have been made recently.
However, in order to minimally understand the value and significance of these important discoveries, it is necessary to see, albeit very briefly, how the scientific knowledge on human evolution came into being.
1.1.- Neanderthal Man.
It was just 150 years ago that the first human fossils were discovered that would eventually be recognised as not belonging to our species. In fact, in August 1856, some quarrymen were blasting limestone rocks in the Feldhofer cave, very close to Düsseldorf (Germany), when they noticed that among the remains was the upper part of a skull (the calvaria or calotte), as well as the remains of other parts of the postcranial skeleton. They collected them and showed them to one of the owners of the quarry, Wilhelm Beckershoff, who, thinking that they might be the fossilised bones of a prehistoric bear, gave them to a local professor of natural sciences, Johann Karl Fuhlrott. He soon realised that they were human. Fuhlrott decided to show these remains to a renowned specialist: Hermann Schaaffhausen (professor of anatomy at the University of Bonn). Schaaffhausen stated that they must belong to one of the oldest human races. Perhaps he could have been a barbarian who lived in northern Germany a few thousand years ago, before the arrival of the Celtic and Germanic tribes.
However, we now know that, in fact, in 1829, several human remains were discovered in the Belgian town of Engis. Among them was one, Engis 2, which belonged to a human from the same subject as the one found in the Feldhofer cave. In 1848, in the Forbes quarry in Gibraltar, more fossils with this peculiar morphology were found; it was a female skull * (2) . However, neither the Belgian specimen nor the Forbes Quarry specimen were recognised as prehistoric humans different from us. Moreover, no work was ever published on them. And yet, Engis 2 are the first remains found of humans other than our species, namely the remains of a Neanderthal child.
The idea that mankind had been created just over 6000 years ago was deeply rooted in the mindset of the time, including the scientific community. A few years after Engis' finding , Boucher de Perthes, a French customs inspector, discovered curiously shaped stones on the gravel terraces of the Somme River. They looked like hand axes. In 1858, two years after the discovery of Feldhofer's human remains finding , it was calculated that they must be about 30,000 years old. It could therefore be assumed that mankind was older than had been predicted. Today we know that they are real hand axes and that they are about 400,000 years old.
However, the great conceptual shift came the following year, when Charles Darwin published his famous work, The Origin of Species. One of the great merits of his book was that it paved the way for popularising and rooting (both in the scientific community and in society) the idea that currently living species existed because they had evolved from previous extinct species; and that these, in turn, had evolved from the same outline. And so on, until we arrive at a first living being that would be the common biological ancestor of all later living things, including us.
Between 1857 and 1858, those who looked at the bones of the Neander Valley specimen interpreted them as those of a man of our species, but with a "peculiar" appearance. A German anatomist was struck by the arched shape of the femurs and deduced from this that he must have been a person who spent a large part of his life on horseback. From this he surmised that he must have been a Russian Cossack who, perhaps wounded during the pursuit of the Napoleonic army during its retreat from Germany in the autumn and winter of 1813-1814, took refuge in the cave where he eventually died. Another anatomist noted the robustness and rusticity of the cranial vault (which included a forehead leave and fleeing, in clear contrast to ours: high and vertical; as well as exaggeratedly prominent supraorbital bony ridges, practically absent in our facial anatomy), concluding that he was an old Dutchman. For another scholar it was a sick German, who had broken his elbow without ever having healed. Both facts were true; but from this he concluded that the severe pain forced him to frown constantly and that his anguished pain became fossilised, giving rise to these prominent supraorbital tori or arches.
Now, after the publication of The Origin of Species, the idea that human forms existed before our own was already conceivable. And, once the intellectual attitude was in place, it would be possible to identify them in the fossil record. However, the task would not be easy. test was the case of Thomas Huxley, a fervent defender of Darwin's evolutionary theory, who rejected that Feldhofer's fossils were representative specimens of a human species prior to us and intermediate between apes and present-day humans, since he found them more similar to the former than to the latter.
Williams King, professor of anatomy at Queen's College, Galway, Ireland, first proposed, in 1861, that the Feldhofer fossils belonged to an earlier and distinct human species: Neanderthal Man (Homo neanderthalensis). The issue, with difficulty, was beginning to get on track. Although it was difficult to accept King's proposal , this eventually prevailed, as in 1868 more "ancient" human remains were found, as much as those in the Neander Valley, although they were much more modern in appearance, so much so that they were similar to us. So we could be sure that they were our direct ancestors and relegate the Neanderthals to an extinct side line. This made it possible to renounce direct kinship with Neanderthals while retaining the central idea of Darwin's theory of evolution that modern humans were descended from extinct ancestors, but that they had to be slender and stately in our case. The idea was born that our direct ancestors were Cro-Magnons and not Neanderthals. In both the late 19th and early 20th centuries, more and more Neanderthal and Cro-Magnon remains were found.
1.2.- The man standing speechless.
In 1887 the Dutch physician Eugen Dubois (1858-1940) went to the Dutch East Indies (present-day Indonesia) with the explicit intention of finding there the missing link between humans and apes. It is curious that a convinced Darwinist, as was the case with Dubois, should look for the missing link in Southeast Asia, when it turns out that Darwin predicted that the origin of man should be in Africa, as it was there that humans with the most similar morphologies - that of the great apes - lived together.
After four years of fruitless searching, in 1890 he found a calotte (the cranial vault), and in August 1891 a femur and a molar. With these specimens he named a new human species, which he called Pithecanthropus erectus (upright ape-man) and Pithecanthropus alalus (speechless ape-man) * (3) . Naturally, the scientific community was sceptical and expressed its reluctance to admit the status of an intermediate specimen between humans and apes that Dubois attributed to Pithecanthropus. In fact, the Dutch scientist himself eventually disavowed his finding. Today we know that these human remains correspond to Homo erectus, and that they are slightly more than a million years old. For a long time it was thought that these humans had lived from just over 1.5 million years ago to about 300,000 years ago (Zoukoudian in China). But new dating offered by geochronologist Carl Swisher's team in the second half of the 1990s insists that Degree erectus may have occupied a chronological range from over 1.7 million years ago (1.7 Ma.) to about 30,000 years ago (30 ky.).
In 1905, a jawbone was found in Mauer (Germany) near Heidelberg, which was almost 500,000 years old and clearly human. It was very robust and it was decided to assign it to a new human species: Homo heidelberguensis. Throughout the 20th century, more remains of this species appeared: Bilzingsleben (Germany), Boxgrove (England), Aragó (France), Petralona (Greece) or the Sima de los Huesos (in Atapuerca, Spain), are some famous examples of sites that have yielded human remains of this species. The Sima de los Huesos is particularly noteworthy for having yielded almost 4,000 fossil remains, including the three most complete skulls in the world fossil record; one of the three oldest pelvises preserved in its entirety; in addition, absolutely all the bones of the human body are represented at this site. So far, a minimum number (nmi) of 28 individuals have been identified, so that a comparative study of a Middle Pleistocene population has been made.
1.3.- The hominids of South Africa.
In 1924 miners presented Raimond Dart, an Australian anatomist based in South Africa, with a fragment of rock containing the skull of a child found in the South African town of Taung. As it was evident that it belonged to a child specimen, it became popularly known as the "Taung Child": The "Taung Boy". Dart realised that it did not belong to any human species, but was much older, and eventually attributed it to: Australopithecus africanus (literally: African southern ape or South African monkey) * (4) . From his analysis of the skull he deduced, from the position of the foramen magnum, that it was a bipedal being. The foramen magnum is an orifice through which the skull is joined to the vertebral column and which in bipedal beings occupies a position more towards the base of the skull, while in quadrupeds, having the spine in a horizontal position, it is located more towards the back of the skull.
Initially, Dart had major problems with the scientific community, which, almost in its entirety, did not accept his theories, basically for two reasons. One was of a conceptual nature and was marked by the connatural reluctance of the scientific community to accept entrance this subject of proposals and on the other hand, the intellectual panorama of human evolution was dominated at that time by the paradigm proposed by Piltdown Man: a human skull with an ape jaw. As Dart's specimen did not fit in with this outline it was rejected. Moreover, as incredible as it may seem, the role of prejudice also played a role: how could we accept that the origin of humanity was in Africa and not in Europe? And as if all this were not enough: more copies were needed. These did not appear until 1936 when Robert Broom found more cranial remains of A. africanus in the Sterkfontein cave near Johannesburg. In 1947 new remains of africanus were discovered in Makapansgat. After having been severely ostracised, Dart was rehabilitated. Indeed, those who had claimed that the "Taung's Child" was an aberrant form of primate had to rectify themselves and acknowledge that it was a new species. Some even admitted that they were the forerunners of the human genus. Moreover, in 1947 it was discovered that Piltdown Man was nothing more than a fraud, a huge hoax.
But Broom not only found more fossils of Africanus, he also found remains of a new species of hominid: Australopithecus robustus (although some people include it in a different genus: Paranthropus robustus, a term coined by Broom in 1938 after finding remains of this at Kromdrai and Swartkrans subject). The specific name (robustus) is a bit misleading, because from the neck down it would be, more or less, like a modern chimpanzee.
2.1.- Paranthropes and the first Homo.
From the late 1950s onwards, the Tanzanian Olduway sites came to the world's attention. Indeed, the most important discoveries of the time were made there. After more than two decades of arduous and unsuccessful work, Louis and Mary Leakey found in 1959 the remains of a Paranthropus boisei (specifically named after their patron) * (5) , which was dated to 1.8 million years ago.
A few months later (on 2 November 1960), fortune smiled on the Leakeys again, for they found, also at Olduway, the fossilised remains of the oldest human species found to date: Homo habilis, at almost 2 Ma. They called him so because his remains were found near some admittedly "rudimentary" tools, not far from which the boisei had appeared before, but whose difficult manufacture did not match the archaic appearance of the boisei.
The decade was characterised by a discussion about the true status of habilis, as it was true that the few remains found of its post-cranial skeleton were reminiscent of that of Australopithecus. A discussion that is still alive today.
In 1967, Yves Coppens and Camille Arambourg found the first remains of a new species of Paranthropus in a site on the Omo River (in southwestern Ethiopia), which they called aethiopicus. It was a jaw that was about 2.6 Ma. All Paranthropus are characterised by a notorious sagittal crest (a sharp bony ridge located in the upper central part of the skull and running from the front to the back, giving the subject a certain punkish appearance) whose purpose was to serve as an anchorage or insertion point for a powerful musculature designed to move a notoriously robust jaw that allowed it to chew very abrasive food. Paranthropus also shared very pronounced zygomatic arches (the bones that form the cheekbones), so that the cheekbones protruded far outwards from the face.
Lucy. The most famous hominid.
In the 1970s the star was "Lucy". It is a female Australopithecus afarensis (so called because it was found in 1974 in the Ethiopian town of Hadar, in the country of the Afar). At 3.2 Ma, it was, at the time, the oldest known hominid, hence its discoverers called it the "mother of mankind". The reconstruction of its hip, as well as other details (such as the shape of the neck of the femur or the bones of the feet) made it possible to determine that it was already a clearly bipedal being. As luck would have it, more than half of its skeleton was found. A year later, the remains of eleven more afarensis were found, group colloquially known as "the first family" * (6) . Unfortunately, the war that broke out from 1976 onwards between Somalia and Ethiopia, which took place in the Ethiopian Ogaden desert, whose western foothills are not far from Hadar, prevented the research team working in that area (led by Donald Johanson, Tim D. White and Yves Coppens) from returning to work for some time.
In the late 1970s the family tree of human evolution was very simple: Australopithecus afarensis was the oldest known hominid and would have given rise to Africanus on the one hand (which would have given rise to Paranthropus, an extinct evolutionary branch) and Homo habilis on the other; the latter would have given rise to Homo erectus which would have given rise to Neanderthals on the one hand (who would have become extinct without leaving descendants) and to us: Homo sapiens. And that's it. That was it. It was as simple as that. But the mysterious plot of human evolution held many, many surprises for researchers. Surprises that were not long in coming.
The 1980s saw the resurgence of surname Leakey. Indeed, in August 1984, 22 years ago, Kamoya Kimeu, one of the most famous members of the "hominid gang", found in Nariokotome (on the eastern shore of Lake Turkana in Kenya) the skeleton of a boy who was 1.6 Ma. The so-called "Nariokotome Boy" or "Turkana Boy", died, probably when he was 11 years old. At the time of his death he was already over six feet tall, and, possibly, once he had completed his development he could have reached six feet. His skeleton sample has a graceful anatomy reminiscent of our own. To which species should he be assigned? Richard Leakey decided to name it: Homo ergaster (meaning: Working Man).
3.1.- In search of the roots.
The 1990s marked a new impetus for palaeoanthropological work. Indeed, peace between Ethiopia and Somalia allowed researchers to return to the country, and the results were not long in coming. On 17 December 1992, the team co-led by Tim D. White (the star palaeontologist of the decade thanks to his exceptional discoveries), Gen Suwa and Berhane Asfaw, found a hominid tooth in a site, Aramis, in the middle course of the Awash River in Ethiopia. They subsequently found half a hundred hominid fossils, belonging to at least 17 individuals, mixed with 600 remains of other animals. As the hominid bones showed numerous fractures, it can be assumed that they were a feast for large carnivores.
The remains were 4.4 Ma. old, the oldest known evidence for the existence of hominids. They were initially assigned to the Australopithecus ramidus clade * (7) . However, it had a set of characteristics: large canines and thin tooth enamel, hominids have small canines and thick tooth enamel, and the shape of the skull made them more similar to chimpanzees than to Lucy. This led the researchers to suspect that this was not just another species of australopithecine. However, it did not appear to be an anthropoid. As Berhane Asfaw pointed out, this species had already separated from the great apes and had begun to evolve into what would become humans. So in 1995 they changed the name and created a new genus for these fossils: Ardipithecus ramidus. Ardipithecus means "ground primate" and ramidus means "root", thus emphasising that its discoverers considered it to be at the base or root of the hominid family tree.
Although today the Awash area is very arid and semi-desert, 4.4 Ma ago it was a forested area. If, indeed, the Ardipithecines were bipedal hominids, then all our knowledge and assumptions to date regarding the origin of bipedalism must be reconsidered. Indeed, it was traditionally held that bipedalism, one of the distinctive features of hominids, would have arisen in the savannah when the rainforest had retreated to a savannah landscape; or when the subtropical woodlands had shrunk, creating clearings in a semi-forested savannah-dominated habitat, so that primates occupying these habitats must have adapted to the new circumstances by evolving bipedalism as a means of locomotion to move between clearings in order to move from copse to copse. Along with bipedalism, they would have retained the skill to climb trees in order to spend the night in them, seeking refuge from large predators. However, if ramidus was already bipedal, this whole theory about the origin of bipedalism falls apart. And all the evidence seems to point in the same direction: bipedalism emerged among hominids when they were still living in a dense environment of trees, so bipedalism was not an adaptive response to the emergence of the savannah, since it already existed as an effective means of locomotion among hominids almost three million years before the savannah made its appearance in the geographical areas occupied by hominids.
3.2.- Abel. The australopithecine of Chad.
The next hominid to break through in the 1990s was Abel. At 3.5 Ma, it surprised the entire scientific community because it was a specimen of Australopithecus found in the Chadian locality of Bahr el Ghazal. For this reason, the director of the team that discovered it, Michel Brunet (director of the laboratory of human palaeontology of the University of Poitiers, France), decided to include it in a new genus of australopithecine which he called: Australopithecus bahreghazali * (8) . Abel was found in 1995 and made public in 1996. Although it is only a mandible with seven teeth, and although some do not accept that it is a proper species of australopithecine but consider that it must have been a local variant of Australopithecus afarensis, Abel has the surprising fact that it was found 2,400 km west of the usual areas of Ethiopia and Kenya where australopithecine specimens from east-central Africa have been found. Whether Abel is a bahrelghazali or an afarensis, his finding shows that three and a half million years ago the australopithecines had undergone a radiation, probably from east-central Africa, which had led them to overcome the geographical barrier represented by the Rift Valley and had spread at least as far as the present territories of Chad. Following Abel's finding , doubts arose about hypotheses about the local origin of Australopithecus.
3.3.- The Lake Turkana australopithecine.
In 1995 a new species of australopithecine was discovered at finding : A. anamensis * (9) which, at 4.2 Ma. old, is to date the oldest specimen of this hominid genus. Its remains were found in Kanapoi and Allia Bay, both on the shores of Lake Turkana. There, the team led by Meave Leakey (director of the palaeontology division of the National Museums of Kenya, in Nairobi) and Allan Walker (professor of anthropology and biology at Pennsylvania State University, USA) found a jaw with clear archaic features that brings anamensis closer to chimpanzees, as this jaw has a tendency to look like a U, like that of the apes mentioned, while the human jaw is V-shaped.
However, the tibia that was found distances anamensis from chimpanzees. Indeed, the tibia of chimpanzees has a "T" shape. In contrast, the tibia of anamensis, like that of humans, widens at the top of the bone in order to accommodate a greater amount of spongy tissue, the purpose of which is to absorb the stress of bipedal movement. In fact, the tibia of anamensis is very similar to that of afarensis, only a whopping one million years older.
The humerus of anamensis also has very modern features. Large African anthropomorphs (gorillas and chimpanzees) move by means of a very specific quadrupedal locomotion subject : they rest their forelimbs on the middle phalanges of their fingers (not on their knuckles, as it is often said). This way of moving is technically known as "knuckle walking" and has a very singular effect on the humerus. In effect, it produces the appearance of an oval hole in the lower part of the humerus, just where the ulna fits in, thus making the joint with the elbow firmer. It is obvious that humans, because they do not move in this way, do not have such a hole; well, neither do anamensis. This is further evidence that these australopithecines were already efficient bipeds, test .
In 1998 more fossils of anamensis * (10) were discovered. And this same year, 2006, the announcement was made of more specimens of this species, finding , with the peculiarity of having been found in Ethiopian and not Kenyan sites, very close to where the remains of Ardipithecus had been discovered. We will therefore return to Australopithecus anamensis* (11).
3.4.- Garhi: The big surprise?
The latest australopithecine to join the hominin family for the time being is Garhi. In 1997 the team of Tim D. White and Berhane Asfaw found (at the Hata beds site in the town of Bouri) in the middle course of the Awash River (near where the remains of ramidus were found) a skull of 2.5 Ma. Its endocranial volume is 450 cc, not bad for an australopithecine of that age. Its teeth were similar to those of early humans, which are of a similar age, but the lower half of its face is prominent like that of the great apes, bearing a strong resemblance to that of afarensis. Its skull is so strange that its discoverers have named this new species of australopithecine Garhi. Garhi means "surprise" in Afar. The finding was unveiled in 1999 * (12) .
But garhi's biggest surprise is that it appeared relatively close to fossil remains of horses, antelopes and other animals, which showed traces on their bones typical of the marks left by a lithic tool when the bone is removed. An antelope jaw has marks that suggest they were made when the language was removed. One of the bones of an antelope was probably cut open at the ends in order to extract the marrow, one of the most nutritious parts. If confirmed, this would be evidence of meat consumption by australopithecines. But, more importantly, it would also confirm that they used stone tools, and the logical question would be whether they also produced them.
The finding of some leg bones and some arm bones suggest that garhi had upper limbs as long as lower limbs. This contrasts with both humans (who have longer lower limbs) and other australopithecines (who have longer upper limbs). This would mean that in the history of human evolution the lengthening of the legs preceded the shortening of the arms. But it is not known why this was the case. In any case, it has yet to be confirmed that the arm and leg bones to which we have alluded belong unquestionably to garhi.
It also remains to be confirmed that they were the first to make tools, as they could have been made by Homo habilis or Homo rudolfensis.
3.5.- Homo antecessor and Homo cepranensis.
During the 1990s in Spain there were some very important discoveries. One of the most noteworthy is proposal of a new human species, by the Atapuerca team. Indeed, on July 8, 1994, the paleontologist Aurora Martín discovered a human tooth in level TD 6 of the Gran Dolina site (since then, the place where it appeared has been called the Aurora Stratum). The tooth was around 800,000 years old and was, at the time, the oldest human remains found in Europe. That morning, amid great excitement, more human fossils were found belonging to at least six individuals. Two died when they were three or four years old. Another was between 9 and 11 years old. Another would have been 13 or 14 when he died and two were under 20 at the time of his death. But... What was the cause of death? Atapuerca held a big surprise: the marks of anthropogenic origin (i.e.: caused by other humans) on their bones suggested that they were the victims of a cannibal holocaust, the oldest known to date. Why were they eaten? Was it for "religious" reasons, say, to keep their spirits in them, or was it more an act of anthropophagy out of sheer starvation, or was it perhaps for hygienic reasons, such as to prevent the corpses from decomposing and to keep large predators away? Y... Who ate them: members of the same species or humans of a different species? Not all questions can be answered at the moment, but the fact that these human bones were treated in the same way as the other animals (in fact they were found mixed in with them) points to the idea that these humans were just another food item on the per diem expenses of those who ate them.
The remains found in level 6 of the Trinchera Dolina (TD) have been assigned to a new human species: Homo antecessor * (13) , whose origin would be in Africa because, according to the theory of its discoverers, it would have come from there, having arisen from Homo ergaster (which we have already mentioned). But this point, core topic in its genealogy, has not yet been empirically confirmed with the finding of Homo antecessor remains in Africa.
What does seem to be more solidly grounded is that these antecessors would be the direct predecessors of the humans found in the Sima de los Huesos, a few metres from the Gran Dolina: Homo heidelberguensis; who, in turn, would have given rise to the Neanderthals.
In the same year that Homo antecessor was discovered in Spain, a human skull between 800,000 and 900,000 years old was discovered in Italy, in the province of Frosinone (89 km southeast of Rome). The finding was found during road works and the scientific work was carried out by the archaeologist Italo Biddittu at position . The reconstruction of the skull took a year. Initially considered to be a European Homo erectus, it was later considered to be an ancestor, but finally it has been included in a new species: Homo cepranensis * (14) .
As can be seen, as discoveries were made, new species were proposed. This has been a constant in this branch of science, which sees its activists divided between those in favour of naming many species and those who are more inclined to try to make broader groups that include different forms representative of a wide intraspecific variety.
4.- The latest discoveries.
It was absolutely necessary to explain briefly what some of the great discoveries in human palaeontology have been in order to understand the value and significance of the great discoveries that have been made in the last six years.
At the beginning of the 21st century the situation was as follows:
The oldest hominid was Ardipithecus ramidus at 4.4 Ma (Ethiopia), and there was (and still is) the question of whether it was bipedal or not. Then we had Australopithecus anamensis at 4.2 (Kenya) and the question of whether it was a descendant of ramidus. Then came A. afarensis (Lucy) with an antiquity of between 3 and 3.9 Ma. Its ancestry was unknown and it was claimed to have given rise to A. africanus on the one hand * (15) (and these to Paranthropus) and to Homo on the other. Homo in turn had two species of proto-humans: habilis and rudolfensis which would have given rise to ergaster (the African Homo erectus) and erectus (the Asian version of ergaster). Heidelbergensis would have arisen from erectus (or antecessor) and would have been the ancestor of neanderthalensis, which would have become extinct without descendants. We Homo sapiens would have arisen from some African variant of erectus (e.g. Homo rhodesiensis, which we have not discussed here, and which is represented by the skull of Kabwe, the ancient Broken Hill in Zambia).
This was broadly the picture at the end of the last century. But at the beginning of this century there have been substantial changes and truly astonishing discoveries. Both in number and in their significance and importance.
Indeed, in just six years as many major discoveries have been made in the field of human evolution as in the previous 146 years. And the importance of these discoveries is comparable to those described in the preceding pages.
So far, we have been succinctly presenting the major milestones of human evolution in order to get an idea of the context in which the great discoveries that have been made recently are framed. However, we have avoided the technical data, as it was only a question of having an approximate idea of how the knowledge of our ancestors had been developed over time. From now on, we will pay a little more attention to the technical data.
4.1- The millennium man.
In October 2000 the team led by Martin Pickford (from the department of Palaeontology and Prehistory of the College de France, Paris), Brigitte Senut (from the Muséum National d'Histoire Naturalle de Paris) and Eustace Gitonga (Director of the Community Museums of Kenya, CMK, an NGO founded in 1997) was working in the Tugen Hills in the Baringo region of Kenya. They were not looking there by chance. Indeed, they were. They were looking at sediments that were six million years old, around the time of the split between the lineages that would lead to chimpanzees on the one hand and hominids on the other, so there might be a trace of an early hominid in those sediments. But... But what made the team leaders think that there might be early hominin fossils there? The answer is simple. A very young Martin Pickford had found a hominid molar right there, at the Cheboit site in the Tugen Hills? 26 years earlier, in 1974!
A number of unrelated events * (16) prevented Pickford from returning to work there until the autumn of 2000. On 13 October of that year, fortune smiled on the team. One of its members, Evalyne Kiptalan, discovered a phalanx of a hand at the Kapcheberek site. It was not until the following month that a few more fossils were discovered. On the fourth of November Pickford himself discovered a fragment of a femur at the Kapsomin site. The following day, at the same site, Senut found a right humeral diaphysis and Dominique Gommery another fragment of proximal femur. During the rest of the month, more fossils were found. In total there are fourteen pieces representing a minimum number of six individuals, and it is not known whether they were males or females. What is known is that one of them must have been a very small child, as a baby tooth has been found. Another individual must have been about one metre and forty centimetres tall and weighed about fifty kilograms.
As it was discovered just before the turn of the millennium, its discoverers decided to call it: Millenium man and also Millenium ancestor. However, in February 2001, when the official result of the study of these remains was presented * (17) they decided to change the name of this specimen to: Orrorin tugenensis. The generic name, Orrorin, means, in language tugen, "Original Man", while the specific name, tugenensis, refers to the place where the remains were found: the Tugen Hills.
These fossils are almost 6 Ma. old (arrived at separately by two independent teams of geologists) and were presented to the public at press conference in Nairobi in early December, i.e. a few days after finding of the last remains and without the time to do a proper technical study. This earned them some criticism, but Senut justified this haste by citing pressure from the then President of Kenya, Daniel Arap Moi. Naturally, this haste further increased the natural scepticism of the scientific community when faced with such spectacular hypotheses as those proposed by the Orrorin discoverers advertisement . According to them, his position in the family tree of hominids would be at the base, as he would be the ancestor and last common ancestor of all of them, thus giving rise to the various genera and species of hominids.
Indeed. Its discoverers claim that Orrorin was already a bipedal being with more human-like features than those of australopithecines. For example, Orrorin's teeth have the peculiarity of being small, which is interpreted as a modern trait, but with thick enamel and set in a strong jaw, representing archaic characters. Analysis of these teeth reveals that Orrorin's per diem expenses was basically frugivorous, although it is assumed that it must have occasionally eaten meat.
The most contentious issue is the supposed bipedalism of Orrorin. That bipedalism was one of the means of locomotion of the Lukeino specimens is something that its discoverers deduced from the study of the structure of the femur fragments found. According to the researchers, their bipedalism must have been at least as efficient as that of "Lucy". However, these femurs are missing the part that corresponds to the knee joint, without which it will be difficult to irrefutably prove their bipedalism, providing only the anatomy of the femur as test . One of the femur fragments has two marks that could very well correspond to those produced by the canines of a large predator; this suggests that the tugenensis in question may have been hunted and eaten by a big cat.
Regardless of whether Orrorin was bipedal or not, what seems certain is that it retained the skill to climb trees, as the small phalanges of the hands and the lateral straightness of the humerus suggest. It is possible that they slept in the trees at night to protect themselves from predators. What does not seem likely is that they moved through the trees by swinging from branch to branch (brachiation), as orang-utans do today.
But the controversy related to Orrorin does not only refer to its supposed bipedalism, but also extends to the position it occupies in the family tree of hominids proposed by Pickford and Senut; a controversy that is heightened by the form that these scientists attribute to this tree. For these French researchers, the phylogeny of the hominid family would be as follows: starting with Samburupithecus (a hominoid from the Upper Miocene that could be between 10 and 9 Ma, and whose remains were found at the Samburu Hills site, not far from where those of Orrorin * (18) ) between 9 and 8 Ma. ago. The Ardipithecus lineage, which would give rise to the Ardipithecus on the one hand and the hominids on the other, could have evolved from this lineage; Pickford and Senut rule out the possibility that the Ardipithecines are part of the hominid lineage, which would rather have given rise to the genus Pan (which includes the two species of chimpanzees that exist today: Pan paniscus -bonobos- and Pan troglodytes -common chimpanzee-). Between 8 and 7 Ma. ago, Australopithecus would also have separated from the evolutionary lineage that would give rise to hominids (something that totally revolutionises the family tree of hominids). Orrorin would be the first genus of hominids which, through thePraeanthropus * (19) would give rise to the genus Homo. This genealogy clashes head-on with all the proposals to date, reviving the old and recurrent controversy about the shape of the hominid family tree.
Those in favour of considering Ardipithecus as the first hominid argue that Orrorin is not sufficiently proven to be a hominid, claiming that it could be one of the last hominids of the Miocene or even the last common ancestor of hominids and anthropomorphs. What is the true status of Orrorin? At the moment it may be too early to determine, but we may well be looking at the first hominid, if not the first hominid, then at least one of the first * (20) .
4.2- The oldest Ardipithecines.
A few months after the advertisement of the finding of Orrorin tugenensis, Yohannes Haile-Selassié announced * (21) the finding of new fossil remains assignable to the genus Ardipithecus. These fossils include a mandible with teeth, bones of the hand and foot, fragments of the arm and part of the mandible, belonging to an nmi 5. The size of the lower jaw and the size of some bones suggest that its stature must have been that of a modern chimpanzee. Firstly, they were assigned to a subspecies of Ardipithecus ramidus: Ardipithecus ramidus kadabba (this means that the 4.4 Ma. ardipithecus remains found in the 1990s and discussed above should be included in the subspecies: Ardipithecus ramidus ramidus), stating that they are between 5.2 and 5.8 Ma old. This last figure brings ramidus kadabba very close to the age of Orrorin (remember that the age of the remains of this genus of hominid is between 5.8 Ma and 6 Ma). This data, in relation to other data related to dentition, will be very interesting to venture a hypothesis that we will comment on later: that, in the opinion of the team led by Tim D. White, Orrorin, Ardipithith Ardipith and Orrorin are very close to the same age. Orrorin, Ardipithecus and Sahelanthropus could be members of the same genus.
The persistence of archaic features in the dentition and the back of the skull indicate that ramidus was phylogenetically close to the common ancestor of hominids and chimpanzees. Kadabba at language Afar means "basal family ancestor" and thus refers to the belief of its discoverers that the Ardipithecines are at the base of the human family tree.
Three years later, in 2004, a new study was published * (22) which included the presentation of more fossils (this time from the site of Asa Koma3) and concluded that the remains of A. r. kadabba should be elevated to species status. Thus, a distinction must now be made between: Ardipithecus ramidus and Ardipithecus kadabba.
Fossil finds of A. kadabba include a phalanx of the foot. As it has a proximal joint with an orientation very similar to that of humans, it is inferred that its locomotion must have been bipedal. "However, a single phalanx is not a conclusive test on the mode of locomotion of any species and we must await the publication of new fossils to know whether or not Ardipithecus was bipedal" * (23). When the discovery of the Kadabba fossils was published in July 2001, the hominid status and bipedality of Orrorin was at plenary session of the Executive Council discussion . It is still not absolutely certain that Orrorin was an effective biped and as the definitive results on the anatomy of ramidus have not yet been published, there is still uncertainty as to whether it was a biped or not. In the event that ramidus is shown to have been bipedal, it would appear that bipedalism would have begun in a wooded environment and not in the savannah, as had been believed until recently. The environment in which Orrorin, whose discoverers also say that he was bipedal, moved was also wooded, and open forest was also the habitat occupied by Sahelanthropus, the oldest of the candidates for the first hominid, which we will see below.
4.3.- Toumaï: The oldest hominid?
In July 2002, just one year after the advertisement of finding of more fossilised remains of Ardipithecus, Michel Brunet (the discoverer of Australopithecus bahreghazali) together with his collaborators of the Mission Paleoanthroplogique Franco-Tchadienne (MPFT), announced * (24) the finding of some fossil remains that could be close to 7 Ma old. Its discoverers attributed them to a new genus and a new species of hominid: Sahelanthropus tchadensis; the generic name refers to the African region of Sahel, bordering the southern Sahara, where the fossils were found. The specific name is a tribute to the country where they were found.
If these data (the antiquity and hominid status of Sahelanthropus) are confirmed, we would be looking at the oldest fossil remains of the hominid family, finally entering one of the most important moments in the history of human evolution: the period of the divergence of chimpanzees and hominids from their common stock.
The finds were made in July 2001 and consist of a nearly complete skull, two jaw fragments and three teeth. These remains are believed to correspond to an nmi. 5 (a minimum number of five individuals).
However, the dating of these fossils is still controversial * (25). This has been done by comparing the fauna of the Toros-Menalla fossiliferous area in the Djurab desert in northern Chad with other sites with similar faunas. Comparison of the faunas suggests that the Toros-Menalla fossils may be between 6 and 7 Ma old.
The skull represents the holotype (paradigmatic specimen) of this species and is preserved in fairly good condition, although its right side is almost completely flattened. The surprising thing about this skull is that its posterior part resembles that of a chimpanzee, but its anterior part resembles the face of a hominid of about 2 Ma. On the other hand, its teeth are small, and although its canines are more primitive than those of Ardipithecus, this would seem to reinforce the relationship between tchadensis and the human lineage. In any case, in Chris Stringer's opinion, Toumaï presents a combination of traits "not seen in any fossil ape [nor] in later hominids" * (26).
Its discoverers have decided to baptise this skull with the name: Toumaï, which in the language goran means: "Life expectancy" and refers to babies born just before the dry season. The technical nomenclature with which this skull is identified is: TM 266-01-060-1, which indicates that it is fossil number 266 from Toros-Menalla). The endocranial volume of Toumaï, and by extension of the Sahelanthropus, is estimated to be between 320 and 380 cc; similar, therefore, to that of present-day chimpanzees. However, the researchers affirm that the global aspect of Toumaï's morphology would not resemble that of chimpanzees, nor that of gorillas, nor that of any of the hominids known to date.
In order to classify Toumaï within the hominid family, it is of paramount importance to determine whether it was already bipedal. As no bones have been found from any of the parts of the body that could give clear clues (feet, hands, arms, legs or hips), it is impossible to affirm the bipedality of Sahelanthropus. To make matters worse, the position of the foramen magnum (the hole where the spinal cord inserts into the skull, which in bipeds is in the basic skull and in quadrupeds in the back of the skull) does not clear up the unknowns. However, its discoverers do not rule out the possibility that tchadensis was already a biped.
If it is confirmed that Toumaï already walked on two legs, then it could be claimed that: "the divergence between the human and chimpanzee lineages occurred earlier than most molecular biology studies indicate" * (27). The conclusion drawn by its discoverers is that: "Sahelanthropus is the earliest and most primitive member of the hominid clade, close to the time of divergence of hominids and chimpanzees" * (28).
However, not everyone accepts that Toumaï unequivocally represents a hominid. Opinions are divided on this issue. Milford Wolpoff, Brigitte Senut and Martin Pickford have so far spoken out against it. According to them * (29) the skull TM 266 looks more like that of a female gorilla than that of a human * (30). Brunet replies to these authors in a text published in Nature just after the above-mentioned * (31). According to the French palaeoanthropologist, it is logical that Toumaï presents archaic and ape-like characters, since we are talking about the oldest hominid found to date.
Hominids from 7 Ma. in central Africa. This has led Brunet's team to question the paradigm held by most members of the scientific community regarding the origin of hominids, known as the "East Side Story Hypothesis". This paradigm, proposed by the French paleoanthropologist Yves Coppens, postulates that hominids would have originated east of the Rift Valley, most likely in East Central Africa, but in any case some 2500 km east of the site where the remains of Sahelanthropus were found. For Brunet's team, this location represents a serious objection to the East Side Story hypothesis, questioning its basic postulate and "suggests that an exclusively East African origin of the hominid family is somewhat improbable" * (32).
To underline the importance of Toumaï's finding , Daniel Lieberman (Harvard University) has stated that in the field of human palaeontology: "it would have an impact similar to that of a small nuclear bomb" * (33). For his part, Bernard Wood (from department of Anthropology at George Washington University) affirms that: "we are gathering evidence that indicates that our origins are much more complex and difficult to trace than any other organism group " * (34). And while he acknowledges that: "Sahelanthropus tchadensis is a candidate at the root of hominids", he also states that "from my point of view it is impossible to prove. My view is that S. tchadensis is the tip of the iceberg representing the taxonomic diversity that occurred during human evolution between 5 and 7 Ma". * (35). To further complicate the controversy, Tim D. White argues that the fossils attributed to Sahelanthropus, as well as those of Orrorin, could perhaps belong to Ardipithecus. As can be seen, the same fact is interpreted in different ways. While Lieberman is convinced that Toumaï is a hominid, Wood doubts it and White, taking the water to his own mill, maintains that it could be an Ardipithecus. In the face of this avalanche of contradictory information dictated by true eminences on the subject website, caution is called for when it comes to pronouncing on such interesting specimens as these, while awaiting the finding of new fossils that could clear up the panorama a little more.
What is the conclusion we can draw from the findings that have been made in recent years concerning the first hominids? First of all, a very important fact must be highlighted: "These three taxa, all more than 5 million years old, have been assigned to three different genera, although each one is based on incomplete material that does not allow for comparison. Where matching parts, such as canines and molars, are available, they are similar to each other, indicating that they may in fact be the same thing, but the evidence does not tell us to whom they might be related, apes or humans. The retention of primitive traits, such as the tapering of the third premolar, does not indicate affinity with apes per se, but neither does the scant evidence for bipedalism indicate affinity with humans. The solution is yet to come" * (36).
Which of the three recently discovered specimens was the first hominid? We do not know for sure. For some the best candidate is Ardipithecus * (37), for others it is Orrorin * (38). For others, as is the case of the prestigious Tim D. White, the similarities between the few remains that coincide would be an indication that would reveal that the three belong to the same genus, which he identifies with Ardipithecus. We are certainly facing an exciting moment in human evolution: the origin of our family. But with the data currently available, it is not yet possible to make a definitive verdict on who was the founding member of the hominid family, the first in a saga that would eventually give rise to our own species.
Will future discoveries unravel this mystery? Some believe so. According to this view, new fossils would settle the question definitively. But other specialists do not take the same view and believe that our ignorance about who was the first hominid and, therefore, the founding member of our biological family, is not a purely circumstantial ignorance that will be resolved with the finding of new fossils, but rather they consider it to be a structural ignorance. Let us explain.
Those who are of this opinion argue that: "if man and the African anthropomorphic apes have a common ancestor, it is obvious that the closer one is to the trunk, the more difficult it is to isolate the ape-like characters of humans. Hence this intense scientific discussion " * (39). Thus: "the closer we get to the divergence or to the common ancestor, the more undifferentiated the characters are and the more difficult it is to decide in favour of one lineage or the other. In fact, there is no magical character that allows us to make a decision.... The history of the appearance of man remains a fragmentary history, with its few certainties (the fossils) and its fragile convictions (the theories)" * (40).
Thus, there is no shortage of difficulties to be encountered by those who seek to determine which was the founding member of our evolutionary lineage. This is why some have graphically described the complexity of this question by stating that: "researchers who try to shed some light on this obscure stage of hominid evolution find themselves like in the fable of the blind men who try to define the shape of an elephant, each of them feeling a different part of the animal (trunk, leg, ear...) and thus drawing a completely different picture in each case. At final, a good puzzle that perhaps reflects the very complexity of human evolution at the peak of the bifurcation between gorillas, chimpanzees and bipedal hominids" * (41).
4.4.- Kenyanthropus platyops: The killjoy.
Like Sahelanthropus, Orrorin or Ardipithecus (both ramidus and kadabba) Kenyanthropus platyops isone of the star discoveries made in recent years* (42).
In March 2001 the renowned palaeoanthropologist Meave Leakey (Director of the Palaeontology Division of the National Museums of Kenya in Nairobi) together with Fred Spoor (from department of Anatomy and development biology at the University College of London) presented the fossils belonging to a new genus and species of hominid: Kenyanthropus platyops * (43) (which literally means: "Kenyan Flat-faced Man"). The generic name Kenyanthropus is a tribute to recognise the important role Kenya has played in the understanding of human evolution through the numerous species and genera of hominids and hominoids discovered in this country. The specific name: platyops comes from two Greek words: platus and opsis meaning, respectively, flat and face, referring to one of the main characteristics of this skull: a flattened face. The generic name is somewhat misleading because the authors themselves recognise that it is not a member of the genus Homo (which includes all human species), nor does it match the morphology of australopithecines. So they were forced to create a new genus. The hypothesis that it is a direct ancestor of man being ruled out, it is thought to be an extinct lateral branch (in relation to humans, of course) of the hominid family tree.
The holotype is a skull catalogued under the abbreviations: KNM-WT 40000 * (44). The skull was found by Justus Erus in the Nachukui Formation on the banks of the Lomekwi River in northwestern Kenya. Numerous fossils belonging to 30 individuals were recovered between 1998 and 1999, ranging in age from 3.2 to 3.5 Ma, i.e. they were contemporary with Lucy. There is no doubt that the finding of Kenyanthropus will be talked about, among other reasons, because of the changes in the genealogical tree proposed by its discoverers. For the time being, they suggest that Homo rudolfensis, until now considered one of the first human beings, should be classified as a species of this new genus. Predictably, this is a proposal which, at least initially, has not been well received by the majority of the scientific community. It is not easy to accept that someone who has been considered a human being for decades should end up in a genus of non-human hominids.
4.5.- Homo georgicus. The Caucasian surprise.
As we saw earlier, when talking about Eugen Dubois, during the last quarter of the 19th century it was thought that the origin of mankind could be in Asia. The finding of Pithecanthropus erectus seemed to corroborate this. But from the second half of the 20th century onwards it was clear that Africa seemed to be the cradle of humanity. This is where the australopithecines and paranthropes, as well as the first humans, came from. This led to the idea that the Javanese were the descendants of Homo erectus, who must have left Africa a little over a million and a half years ago with sufficiently advanced technology to enable them to survive the crossing from Africa to Indonesia and with large brains of around 1000cc. The Tel Ubeidiya site in Israel testifies that humans passed through there 1.4 million years ago. However, a Caucasian site was to shake up, albeit very slowly, all the classical ideas about the first human exodus out of Africa.
The Dmanisi site is in Georgia, about 85 km southwest of the Georgian capital, Tbilisi, and very close to the Turkish border. It was 24 September 1991 and that year's campaign was coming to an end. A German student, Antje Justus, was working carefully and painstakingly in his field when a human jawbone, D-211, appeared. Leo Gabunia and Abesalom Vekua proceeded to study it and were able to determine that it belonged to an adult individual more than 1.7 million years old. This is truly amazing. Humans in the southern foothills of the Caucasus almost 1.8 Ma. Where did they come from? How did they get there? Who were they? These and other questions kept going round and round in the heads of their discoverers.
At that time there was a discussion between the supporters of Long chronology and those of Short chronology. That is to say: between those who argued that Europe had been populated for more than a million years and those who maintained that the first Europeans should not have been more than half a million years old. The doubt was dispelled with the finding of Homo antecesor at Atapuerca (780,000 years old) and with the confirmation, in 1999, by geochronologist Carl Swisher that the volcanic tuff in which the Dmanisi jawbone was found was 1.8 Ma. old, so that the jawbone would be very close to that date.
On 31 May 1999, on level V, the first Dmanisi human skull (D-2,280) was found. On 22 July, the second (D-2.282) was found. The first thing that surprised us was its reduced cranial capacity: 780 cc. for the first one and 650 cc. for the second one, something that put paid to the idea that the first humans who left Africa were provided with a voluminous brain. Specifically, D-2.282, with its 650 cc. was clearly below the lower thresholds of Homo ergaster and squarely in the middle of the Homo habilis range.
On 26 September 2000, when the campaign was over, Gocha Kiladze returned to the site to accompany David Lordkipanidze, Henry de Lumley and Christophe Falguères to take samples of the volcanic ash from level VI. They did not go to the same sector where they had worked in the summer, as it is sealed, but to a cut close to it, 13m away. The second mandible, D-2,600, appears there. On 24 August 2001 they found the third skull: D-2.700. Its capacity is even smaller than that of the two previous ones: 600 cc. At the end of August 2002, Slava Ediberidze finds a fourth skull: D-3.444, which also has a very small endocranial capacity leave: 650 cc.
But Dmanisi had another big surprise in store. It was the fourth jawbone found in August 2003: it had no teeth! It belonged to an adult that had lost its teeth many years before it died. How did it survive? Undoubtedly thanks to the care of the other members of group , who probably even chewed his food so that he could swallow it. If it is confirmed that the humans of Dmanisi had cared for this old man, this would be the oldest known act of human solidarity to date.
Because of the size of the skulls and some of their archaic physical characteristics, it was decided to group them into a new species: Homo georgicus * (45), intermediate between Homo habilis and Homo ergaster/erectus * (46). Dmanisi is a site where research work is being carried out on an area of one hundred square metres, but it is supposed to have a potential wealth of eleven thousand square metres (a hundred times more than has been worked to date!). It is not surprising, then, that Dmanisi is a site to keep an eye on, as it is sure to hold many surprises yet to be discovered.
4.6.- Our most ancient direct ancestors I. Homo sapiens idaltu.
It has always been a great enigma to know who our oldest direct ancestors were. In the late sixties of the 19th century it was assumed that they were the Cro-Magnons, a little more than thirty thousand years old. But in the 1930s in Israel (Mugharet et-Skhul cave or Djebel Qafzeh cave), 90,000-year-old remains of anatomically modern humans (morphologically similar to us but with slightly archaic features) were discovered. Genetic studies developed during the 1980s eventually suggested that our origin was in Africa and that we must be between 150,000 and 200,000 years old. Although there was strong controversy, the numerous studies that were carried out during the 1990s did not fail to confirm this data. But there was no physical evidence. Finally, in 2003, it was made public.
Indeed, on 12 June 2003, the ineffable Tim D. White announced that his team had discovered (in 1997) at the Ethiopian site of Herto (in the middle reaches of the Awash River) * (47) the oldest known human remains of Homo sapiens to date. White has assigned them to a subspecies of our genus: Homo sapiens idaltu. The latter name means "old man" in Amharic, a Semitic language spoken in northern and central Ethiopia. The remains are between 155,000 and 160,000 years old* (48) , and are therefore older than those found at the mouth of the Klasies River (Klasies River Mouth, South Africa), which could be up to 120,000 years old.
One of the most spectacular characteristics of these fossil remains is that they show that they were subjected to ritual cannibalism. If this is confirmed, this would be the oldest known symbolic behaviour to date.
4.8.- Our earliest direct ancestors II. The Omo Kibish skulls.
A year and a half after the advertisement news of the existence of the Herto fossils, new news has come to light about who could be the oldest human fossils of our species.
In 1967 a research team led by a young Richard Leakey (the same man who led the team that found the skeleton of the Nariokotome Boy or Turkana Boy) found two Homo sapiens skulls in the Kibish Formation on the banks of the Omo River in Ethiopia (located a few hundred kilometres south of Herto).
Two problems soon arose in connection with these skulls. On the one hand, Omo I had markedly more modern features; on the other hand, there was the question of dating. First, it was assumed that they were about 130,000 years old, which was in itself very old. Later it was claimed that they could be up to 160,000 (the same age as the Herto remains). But in February 2005 Ian McDougall (Australian National University, Canberra), Francis Brown (University of Utah) and John Fleagle (Stony Brook University, New York) published an article in the journal Nature* (49) in which they stated that the new dating of the two skulls (technically known as Omo I and Omo II, and anatomically modern in constitution) gives them an age of 195,000 years.
To do this new dating, McDougall's team went to the same place where the skulls were found to collect rocks on which the fossil remains had been deposited. Fortune smiled on them and, in addition, they also found a sapiens femur. The analysis of these geological testimonies, using different dating methods, led these researchers to maintain that the age of these anatomically modern human remains may well be 195,000 years old. They would thus be the oldest human remains of members of our species. However, the authors of this research themselves acknowledge that there is a possibility that the fossil remains are 104,000 years old, although they believe that the higher date is more likely.
If the "long chronology" for these remains is confirmed, it would corroborate the hypothesis that the origin of our species is in Africa ("Out of Africa" hypothesis); this would also agree with the vast majority of genetic data, which states that our species originated on that continent between 150,000 and 200,000 years ago. What is less clear is Francis Brown's view that modern human behaviour appeared 50,000 years ago. Data from Henshelwood in South Africa (Blombos Cave and Klasies River Mouth, for example) seem to testify to the existence of clear signs of modern human behaviour, expressed through the cultural elements that have come down to us in the archaeological record, from at least 80,000 years ago* (50).
4.9.- The little human of the Island of Flores.
At the end of October 2004, Mike Morwood and Peter Brown announced to the world the existence of a new human species: Homo floresiensis * (51). The news caused great admiration in the field of human palaeontology and was listed by the magazineScience as the finding of the year. It was a hominid little more than a metre tall and with an astonishingly small brain (at the time it was estimated to have an endocranial volume of 380 cc, similar to that of a chimpanzee). It was attributed to the manufacture of tools from the Mousterian subject (the same as those used by Neanderthals and Sapiens more than 50,000 years ago). According to Morwood and Brown, it would have descended from Homo erectus and would have evolved towards its peculiar morphology due to geographical isolation, becoming extinct around 18,000 years ago.
After much controversy, its discoverers, in collaboration with the palaeoanthropologist Dean Falk and the radiologist Charles Hildebolt, published the results of their study of the LB1 skull (the acronym refers to the site where it was found: the Liang Bua cave) * (52). The new volume now assigned to the brain is 417 cc. * ( 53), a figure that includes it within the parameters assigned to the gracile Australopithecus, subject Lucy, 3 million years ago. However, what struck Falk most was not so much the volume, but the structure of the brain: a size typical of an australopithecus but with a clearly human structure. The brain does not fossilise, but leaves unmistakable marks on the inner wall of the skull (the endocranium). The study of the endocranium of the Liang Bua hominid has revealed that it had highly developed temporal lobes (areas that in our genus are associated with language comprehension, including Wernicke's area and Broca's area) and the frontal lobe (area associated with the control of rational skills and planning for the future). These data allow us to speculate with the possibility, as it is only a hypothesis, that Homo floresiensis was able to plan complex future actions, as well as to master some form of spoken language.
From the very moment of the presentation of this new human species, the controversy around it has been very lively. In the first place there are researchers (Collin Groves) who believe that Homo floresiensis could have evolved from Homo habilis, or from some other human species, previous to Homo erectus, not yet discovered * (54) (possibility considered by Falk, Morwood, Brown * (55) and others). Of course, if this is so, the entire history of the evolution of the entire human race over the last two million years would have to be rewritten. Others (Teuko Jacob, on the one hand, and Maciej Henenberg together with Alan Thorn, on the other) believe that we are in fact dealing with a sapiens who had problems growing up. The Hobbit discoverers' answer is blunt: "We have seven individuals with a similar body, with teeth and with facial proportions like those of the Liang Bua specimen. What is the possibility that they represent the form of modern humans? None" * (56). Giants of human palaeontology, such as Tim D. White and Chris Stringer also disagree with Jacob's interpretation. The controversy has even extended to the custody of and access to the fossils. Until March 2005 they had been in the hands of Jacob (Dean of paleoanthropology in Indonesia and who did not belong to the team researcher) without their discoverers having access to them; however, many of the fossils, fortunately, are now available again to the team that discovered them for their study. Of course, Homo floresiensis is going to give a lot to talk about in the near future, as its fossilised remains have become, for several reasons, authentic "bones of discord" * (57).
Little by little, new studies on the fossil remains of this new human species are coming to light. Thus, on 13 October 2005, Nature published an article signed by Morwood and Brown, among others, in which they announced their latest discoveries about Homo floresiensis. These are human remains belonging to at least nine individuals with anatomical characteristics similar to those found in 2003. The fossils present a set of distinctive features that do not occur among our species, Homo sapiens, the anatomically modern humans: extremely small skulls, with an endocranial capacity that does not exceed 420 cc. (the same that is attributed to the australopithecines of subject archaic, such as the afarensis, whose most famous representative is Lucy, and only slightly above the average brain volume of the chimpanzees, 380cc.). Although the facial features and the size of the teeth clearly suggest that it belongs to the human genus. The bones of the postcranial skeleton (i.e. from the neck down) reveal that the stature of these humans was around one metre tall.
Two years ago it was found (in sector VII of the Liang Bua cave, on the island of Flores, Indonesia) part of the skeleton, including the skull, of an adult female (as can be seen by the shape of the hip) (the wear of the teeth indicates that she must have died when she was about thirty years old), which must have measured just over 90 cm, This is why it was popularly known as: Hobbit, in memory of that tribe of tiny humans that appears in the saga: The Lord of the Rings; although its technical name is: LB1 (i.e.: specimen 1 of Liang Bua). Now fossils have been found that correspond to a three-year-old boy who was about 50 cm tall, and an adult who was even shorter than LB1. These fossils include a new mandible belonging to an adult individual, and postcranial remains corresponding to several specimens, as well as the arm bones of LB1, which were not originally found in 2003. Its discoverers estimate that the fossils found range in age from twelve thousand years old (the date calculated for their extinction before the first humans of our species arrived on the island, at least this is what is assumed for the moment) to ninety thousand years old for the oldest specimens.
The conclusions drawn by Morwood and Brown from the new findings are compelling. The evidence accumulates in favour of the thesis that we are dealing with a new human species that managed to survive until barely 12,000 years ago. The Flores men were humans who did not belong to our species. The fact that all the bones found have proportionally small dimensions shows that Hobbit, the female found two years ago, was not a dwarf woman, but that we are dealing with a human species that is really different from ours; and that presents, as the most relevant morphological characteristic, a diminutive stature. Logically, the duplication of fossil bones reinforces the idea that floresiensis corresponds to a population of tiny humans specifically different from any other human subject , thus ruling out the possibility that the skeleton of LB1 corresponded to an individual affected by a pathology or that it was some anatomically aberrant form of sapiens. Among the new discoveries announced is a tibia that suggests that the individual to which it belonged was no taller than 106 cm, for the moment the tallest Floriensis ever found. Moreover, the three-dimensional analysis of the skull of LB1 has revealed that it does not have the endocranial structure of a microencephalic (a disease that occurs among some people of our species and that consists of having an abnormally small brain), but it shows a normal endocranial structure only with very tiny dimensions.
But why is the physical build of Homo floresiensis so small? In the case of animals, the explanation is relatively simple: Flores is a not very big and small island, where food resources are scarce, so that it is practically impossible to maintain a population of large predators. Consequently, large herbivores no longer need very large bodies as a defence mechanism, as their high energy cost would make survival in resource-poor habitats unfeasible. In this way, natural selection favours the survival of those herbivores that reduce their body volume, so that the species can better manage food resources by making better use of them, thus making their viability possible. However, explaining the reduction in brain volume experienced by Hobbit is much more complex and less well documented in the fossil record. Palaeontologist Salvador Moyà, from the Institut Miquel Crusafont de Sabadell in Barcelona, found fossilised remains of Myotragus in the Balearic Islands, until now considered a Balearic goat species, but which recent studies relate more to sheep and which had reduced the size of its brain by half. Explaining the reduction in brain volume in humans, on the other hand, is extremely complex, as it is a predator (although lions and hyenas, which are also predators, may have reduced their brain volume by a third over the last quarter of a million years). The exact cause of this reduction has yet to be revealed: was it simply due to geographical isolation, or is there some other reason that escapes us for the moment?
Homo floresiensis really raises a whole series of questions that never ceases to surprise both locals and strangers and that can only plunge us into a deep perplexity. They were undoubtedly intelligent beings, despite having a brain slightly bigger than that of a chimpanzee. They hunted dwarf elephants (Stegodon), giant lizards such as the Komodo Dragon (still extant and truly impressive with its two-metre length and its carnivorous per diem expenses ) and other larger ones that are now extinct. They were masters of fire and made complex lithic tools. A complex discussion has been established on this point. For some authors, Richard Klein, for example, from the University of Stanford, the tools could not have been made by the Floriensis, because most of them were found far away from the fossil remains of this species. Colin P. Groves, from the Australian National University, argues that the stone tools found in Liang Bua are too complex to have been made by humans with such a tiny brain and are probably the work of sapiens who inhabited the island at a much earlier date than we know. The researcher team say that this is unlikely, as there are lithic tools that have been dated to more than 90,000 years ago. The most probable thing, then, is that Homo floresiensis was the author of those tools, and in that case there would be no doubt that, as Peter Brown indicates, they were very clever. And yet... their anatomy did not differ much from that of an australopithecine of three million years ago!
What is the origin of Homo floresiensis? The topic is very open, as there are many uncertainties. At the beginning, its discoverers were firm believers that the Floresiensis were descendants of the Homo erectus, who would have arrived in what is now Java and Sumatra 1.8 million years ago (as the findings of Modjokerto, Trinil or Solo indicate, and according to the dating of the geochronologist Carl Swisher). Although those islands were then joined to the Asian continent forming the Sonda Peninsula, Flores never was, it was always isolated by an arm of the sea that acted (relatively) as a biological barrier. This separation is known as "Wallace's Line". Human presence on Flores thus dates back more than 800,000 years, according to Morwood, claiming that this is indicated by the fact that lithic tools have been found on the island at that date. However, there are those who question this, arguing that its morphology is not of anthropogenic origin, but the result of the action of natural agents. However, most of the scientific community tends to credit the testimony of Morwood and Brown. The question then is: How was it possible for humans to navigate such dangerous waters 800,000 years ago? Did they land on Flores by chance? In any case, this fact is part of one of the many enigmas that remain to be solved in relation to the human presence in Flores.
At present, there are three main hypotheses to explain the origin of Homo floresiensis. On the one hand, there is the possibility that they are the descendants of some supposed erectus who would have arrived in Flores some 840,000 years ago (being the possible authors of the tools found in the Sonda depression), and who would have reduced their body dimensions as a means of adaptation to the scarce resources of the island. This was the hypothesis that the authors of the finding have so far favoured. Another possibility is that the Floriensis already arrived on the island with a significantly diminutive size, perhaps as a result of a process of dwarfism undertaken on other islands. This is currently the hypothesis considered most plausible by the directors of the team carrying out the work on Liang Bua. Although, in this case, the question remains as to the species from which the Floriensis would have evolved. However, it cannot be ruled out that these humans already arrived with extremely small body dimensions in Southeast Asia before occupying an island. In such a case, the possibility that they were directly descended from Homo habilis, or Homo georgicus, seems plausible. Not surprisingly, and as we have already seen, since the findings at Dmanisi, in the Caucasus, it has been possible to demonstrate that the first humans to leave Africa were not Homo ergaster (i.e. the so-called Homo erectusafricans; or, to be more precise, the African ancestors of the Asian Homo erectus) but a more archaic human species, possibly derived from Homo habilis: Homo georgicus. More surprising is Milford Wolpoff's proposal , which suggests that the Floresiensis may be descended from Australopithecus and that even these may have left Africa, being the architects of an early exodus to Southeast Asia * (58). Such a risky proposal would have to be based on minimally solid empirical evidence (some fossils that might suggest such a thing) in order to have some margin of credibility. However, nothing of the sort has been found, although Wolpof argues that it has happened, we just don't know how to see it, so that fossils hitherto ascribed first to Meganthropus and then to erectus should be re-examined in the light of the new findings to see if it was possible to ascribe them to Australopithecus. A proposal which is too heterodox and which, before acquiring any credibility, must see how the possibilities of more plausible and less revolutionary hypotheses are exhausted.
The future of Homo floresiensis is very promising. The published findings refer to fossils found in 2004; however, since the end of March 2005 the research team restarted the excavations in Liang Bua. In that campaign they worked on levels that are about 50,000 years old.
Are there more hobbits on the islands near Flores, is that the only place where this strange experiment in human evolution took place, and on the islands around Flores did humans evolve into new species that are as yet unknown to us? To try to answer these questions, M. Morwood went to the neighbouring island of Lombok, west of Wallace's line, at the end of March 2005, to find possible sites of interest for future excavations. However, there are other questions closer to home that still remain: Why did Homo floresiensis become extinct? Were we the cause of their disappearance? Did our ancestors interact with them? They are also trying to recover DNA from floresiensis in good condition to compare it with ours.
In May of this year, the controversy has flared up again. Robert D. Martin and his team* (59) insist that Floresiensis is a human of our species that has suffered from microcephaly, while Morwood and his team do not wield the arguments we have discussed.
As it can be seen, everything related to Homo floresiensis is still to be solved. But there is no doubt that Flores (and who knows if the surrounding islands) still holds many surprises that will come to light in the coming years.
4.10.- Anamensis and the origin of australopithecines.
In early March 2005 Yohannes Haile-Selassié announced that his team had found 4 million year old hominid remains that were already bipedal, but cannot yet be assigned to any genus or species. finding was released at press conference on 4 March 2005. Studies of these remains have yet to be published. Nature reported the news in a short grade signed by Rex Dalton * (60).
What is certain is that the team of Tim D. White (one of the most prestigious and world-famous palaeoanthropologists) had discovered new fossils of anamensis in the Ethiopian locality of Assa Isse. He announced this on 13 April in an article published in Nature* (61). There are about 30 fossils belonging to at least 8 individuals. The remains have been found at the Ethiopian site of Asa Isse (meaning "Red Hill" in language afar) and have been assigned to the genus and species: Australopithecus anamensis, estimated to be between 4.1 and 4.2 million years old. The remains found include teeth (including the largest hominid canine discovered to date, its large size brings it closer to the typical range of apes and is a sign of an archaic character, logical if we take into account that we are talking about the oldest species of australopithecus known to date), part of a femur, some hand and foot bones. Some of them were found in 1994 and others appeared in December 2005.
As mentioned above, specimens of anamensis were already known to be 4.2 million years old. They were found in Kanapoi and Allia Bay, on both shores of Lake Turkana (Kenya) by the team of Meave Leakey and Allan Walker, and were made public in 1996 (in fact, the first fossil of this species was discovered by Brian Patterson in 1964, although it was not assigned to any specific species of hominid at the time). What is surprising about the fossils that have now been found is not their age, but the fact that they were found almost a thousand kilometres north of where their Kenyan counterparts were found, and that they were found very close (a few kilometres away) to the sites where fossils of Ardipithecus ramidus have been found (also found by White's team, as we saw earlier). Although the discussion on the hominid status of a. ramidus is still open, it is quite possible that it is, so that, with its 4.4 Ma. it would be the ideal candidate to be the ancestor of australopithecine australopithecines anamensis. Geographical proximity works in favour of this hypothesis, but the fact that it is 4.4 Ma. old puts it too close in time to anamensis. However, White's team argues that there could have been a case of "punctuated gradualism" (alluding to Gould and Eldredge's theory of punctuated equilibrium, which asserts the possibility of drastic evolutionary changes in a short time; punctuated gradualism would assert the existence of gradual changes in a very short period of time; however, if this is the case, intermediate forms between ramidus and anamensis should be found, which are so far absent in the fossil record). Another possibility (also raised by their discoverers) is that anamensis descended from another, as yet unknown, hominin and that ardipithecines were a side branch (and therefore not directly involved in the emergence of the human lineage) that came to coexist with anamensis. Both hypotheses are consistent with the current data and only the finding of more remains will be able to decide which of the two alternatives is more plausible.
As far as the anamensis lineage is concerned, the consensus among scientists is much greater. It is generally accepted as the direct ancestor of Australopithecus afarensis, the species to which the famous Lucy belonged. Afarensis are australopithecines that lived between 3.9 and 3 Ma. and lived in the same geographic areas where the remains of anamensis have been found, both in Ethiopia and Kenya. So this is the first time that it has been possible to link these three species -ramidus, anamensis and yafarensis- in chronological succession in the same area (the Afar region of Ethiopia). The proximity of the new discoveries raises the possibility that anamensis is the ancestor of afarensis. This August, in the Journal of Human Evolution, Meave G. Leakey (the discoverer of A. anamensis), Donald C. Johanson (the discoverer of Lucy), Yoel Rak and others published an article in which they raised the question of whether or not anamensis was the direct ancestor of afarensis* (62) , betting on it. However, Lee R. Berger, for example, does not see things so clearly and doubts that anamensis can simply be the ancestor of afarensis because, he claims, the skull of the former is notoriously more primitive than that of the species to which Lucy belongs, the remains of the postcranial skeleton seem to be of a more modern morphological subject , and yet the specimens of anamensis are almost half a million years older than those of afarensis. Thus Berger asks: "How was it possible that a creature supposedly more ape-like in its cranial morphology than africanus and afarensis, and which had lived at least half a million years earlier, was more advanced in terms of anatomical evolution from the neck downwards?" * (63).
4.11.- Genetics and human evolution.
In recent years, many other great discoveries have been made (as is the case, for example, of the Miocene hominoid: Pierolapithecus catalaunicus * (64) ) in addition to those mentioned here. But it is not the intention to make an exhaustive list of them, which, fortunately, would make this exposition tremendously long. However, we do not want to finish without mentioning the importance of genetic studies in the field of human evolution carried out in the last fifteen years. And we wish to end in this way for several reasons. Firstly, because genetic studies applied to human palaeontology are proving to be one of the great tools for understanding human evolution over the last 150,000 years. Secondly, because in May 2006 the world's most famous palaeogeneticist, Svante Pääbo, announced that his team had succeeded in sequencing, for the first time in history, Neanderthal nuclear DNA, something extremely difficult and which will be the subject of much discussion in the coming years* (65). Thirdly, because we began this conference talking about the Neanderthals, about how they (their finding) provided the opportunity for the birth of the science of human palaeontology and how now, just when it is 150 years since their birth finding, they are once again the protagonists thanks to the sequencing of a fragment of their nuclear DNA. In this way we give a circular tone to our exhibition. A circular tone which, as we will explain in our conclusions, will in fact end up being an upward spiral.
150 years ago now, in August 1856, the fossilised remains of the first human beings were discovered in Germany, and a few years later they were recognised as the first humans other than our own species. Neanderthal Man was born for science and with him the science of human evolution.
The question that followed was obvious: could these primitive morphological beings be our ancestors? The controversy on this point lasted more than a century, based exclusively on data from the palaeontological and archaeological record. In 1997, a powerful new discovery, tool , was added to discussion: mitochondrial DNA sequencing. The conclusions of that study and those of almost every study to date are the same: almost all genetic analyses of Neanderthal mitochondrial DNA point to the fact that Neanderthals were not our direct ancestors. In other words, they were not our siblings, but perhaps our first cousins. Genetic studies of mitochondrial DNA carried out to date largely suggest that today's humans come from a group of humans who lived in Africa between 150,000 and 200,000 years ago.000 years ago and from there spread to the rest of the world, replacing the human populations they encountered along the way (Out of Africa or Noah's Ark Hypothesis), as opposed to those who believe that present-day humanity has arisen from the evolution of the diverse populations that were once scattered across the Old Continent and Asia and Africa (Multiregional or Candelabra Hypothesis).
In any case, the multiregionalists argued that the proponents of the African origin of all present-day humans (the Africanists) could not present their hypotheses as conclusive until nuclear DNA from Neanderthals was sequenced (for reasons we shall see below). But this view is not only recognised by multiregionalists (a distinct minority among scholars of human evolution); Africanists also admit it. Such is the case of Ayala and Cela Conde who state quite clearly that: "Only the study of the nuclear DNA of Neanderthals will make it possible to obtain conclusive answers in this field" * (66). Written in 2001, these words see today how this is beginning to become a real fact.
Well, that time has come and the results confirm, for the moment, that we are not descended from Neanderthals. Although, for obvious reasons, no definitive statements can yet be made. We will not go into the details of the recent history of genetic studies of human evolution that has culminated in the sequencing of a fragment of Neanderthal nuclear DNA because it is not the subject of this dissertation. But we will have to summarise it very briefly in order to understand the value and significance of the sequencing of a fragment of Neanderthal nuclear DNA.
In the late 1980s Wilson, Cann and Stoneking published * (67) a study carried out with mitochondrial DNA (mtDNA is only transmitted maternally), suggesting that present-day humanity originated in Africa from a single woman. The African Eve or mitochondrial Eve hypothesis was born. These first anatomically modern human populations would have left Africa around 80,000 years ago and spread around the world, replacing indigenous populations as they were found. Opponents argued that populations newly arrived in an area interbred with aboriginal populations (Neanderthals in Europe and Erectus in Asia) to give rise to modern humans. Admittedly, their criticisms of the methods then employed in ancient mtDNA genetic analysis were consistent. But during the 1990s, however, an endless number of studies were carried out, with increasingly refined methods, which continued to yield data in favour of the replacement hypothesis.
It was in 1997 that a major event in this field took place. A team of geneticists led by Svante Pääbo succeeded in sequencing, for the first time, a fragment of ancient mtDNA from a Neanderthal who had lived 45,000 years ago* (68). This is the same individual that was found by miners in August 1856 in the Feldhofer cave in the Neander Valley (as you can see, this is an old friend of ours with whom we began this conference and with whom we will almost finish it), near Düsseldorf, and which was used to name the species: Homo neanderthalensis. The result study of this specimen, Feldhofer 1, also supported the hypothesis that Neanderthals and Cro-Magnons belonged to different species. Specialists such as Ruvolo, Stringer or Ward, recognised that although it was not test final the results indicated that it was highly improbable that Neanderthals had contributed their gene pool to that of present-day mankind. But this was not enough. More studies were needed (in 1999 the team of Pääbo and Krings succeeded in sequencing more mtDNA from Feldhofer 1, yielding the same conclusions* (69) ), preferably from multiple specimens.
Y... they arrived! In 2000, the sequencing of the mtDNA of a Neanderthal child from the Caucasian cave of Mezmaiskaya was published * (70). In the same year * (71) the study of more Neanderthal mtDNA was published; this time from a Croatian specimen: Vindija 75. The conclusions were the same.
The following year a team of Australian scientists supporting the multi-regional hypothesis claimed to have sequenced mtDNA from Lake Mungo Man (one of the earliest Australian sapiens) with an age of almost 60,000 years. As the sequence they obtained was very different from that of present-day humans, they concluded that the replacement hypothesis was plausible. However, the study has fallen into disuse because of the scientific community's rejection of it on the grounds that it does not meet any of the established criteria for authentication of ancient mtDNA proposed by the scientific community in order for this study subject to be valid. Although it was also inconclusive for the usual reasons (the bias of the sample), the results again suggested that Neanderthals had not participated genetically in the emergence of present-day humanity.
In 2003 there was an important new development. In this case, the sequencing of ancient mtDNA corresponded, for the first time, to two Cro-Magnons, Paglicci 12 and 25, just over 20,000 years old. As they were much more different from the genetic samples of Neanderthals than from us, it was once again clear that Neanderthals were very unlikely to be our direct ancestors. There were now Cro-Magnon mtDNAs that did link them directly to us. Although the morphological evidence had been overwhelming for more than a century.
The following year saw the simultaneous publication of the mtDNA analyses of four Neanderthals: the Old Man of the Chapelle aux Saints (France), Engis 2 (Belgium) and Vindija 77 and 80 (Croatia). The Iberian Peninsula, one of the last refuges of Neanderthals, has also contributed to this discussion. In 2005, * (72) made public the sequencing of a fragment of ancient mtDNA from an Asturian Neanderthal from the El Sidrón cave. This analysis also sample significant differences with the same sequences of present-day humans.
What was deduced, then, from all the sequences made from ancient mtDNA of Neanderthals and Sapiens? That: "the weight of molecular evidence favours the hypothesis of a recent African origin of modern humans" * (73). This is why Stoneking and Pakenford conclude that: "direct analysis of mtDNA from Neanderthal fossils and their contemporaries, the anatomically modern humans of Europe, indicates no contribution of Neanderthals to the mtDNA of modern humans" * (74).
Despite all the accumulating evidence, proponents of the multi-regional hypothesis continued to claim that only the study of Neanderthal nuclear DNA could ultimately clarify the doubts written request. Indeed, that is where the genes encoding basic aspects of metabolism, physiology, our external appearance, brain structure, sex, even - perhaps - some behavioural traits are located. There is no doubt that being able to access this wealth of information would be a quantum leap in the study of human evolution. So who has taken this giant step? Svante Pääbo and his team of palaeogeneticists. On 12 May, during a conference held at the Cold Spring Harbor Laboratory in New York, Pääbo announced that he had succeeded in sequencing, for the first time, the nuclear DNA of a Neanderthal, specifically 0.03% belonging to a 45,000-year-old male, whose remains had been found in Vindija.
It should be noted that the definitive study has not yet been published, but some conclusions have already been advanced. First, the date of divergence of the lineages leading to Neanderthals on the one hand and anatomically modern humans on the other has been refined. Previously it was assumed that this time may have been around 600,000 years ago, but it is now believed to have been 315,000 years ago. Secondly, it has been determined that the Y chromosome of Neanderthals was substantially different from that of chimpanzees, which is normal, but also from that of modern humans, which is yet another piece of evidence in favour of the idea that they are a different species from us.
Another criticism of ancient mtDNA studies by multiregionalists was that small DNA strands were sequenced. This is why Pääbo's team is tackling the daunting challenge task of deciphering the Neanderthal genome. The task could be completed within ten years. In the meantime, he has proposed to create a bank of ancient DNA, mitochondrial and nuclear, from Sapiens and Neanderthals, to compare the samples while awaiting the definitive test. Once the genomes of both species can be compared, it will be possible to know which are the specific genes of anatomically modern humans, those of Neanderthals and those common to both and, consequently, those specific to the human genus. In this way, we will be able to know which genes are only modified in Neanderthals and with this, we will be able to aspire to know which genes controlled Neanderthal morphology.
As you can see, the science of human evolution has been in existence for more or less a century and a half, if we coincide (admittedly somewhat arbitrarily, as it is true that other dates could be taken a little more recently) its birth with the date of finding of the Neanderthal fossils from the Feldhofer cave. Of these one hundred and fifty years, the last six years have seen as many spectacular and extremely important discoveries as in the previous 144 years. Both in significance for this field of science and in number.
We are objectively convinced that in the coming years there will be new great discoveries. And pay attention to the names you have heard here, because you can be sure that the Middle Awash River will continue to yield great discoveries, as will Atapuerca (this summer, for example, the fabulous site in Burgos has brought to light new fossils of great importance), Dmanisi (a site we have already said that only a very small part of its potential wealth is being investigated; what will happen when excavations are extended to other parts of the site? Don't doubt it, all indications point in the same direction: more human remains are sure to appear), Lake Turkana or the Djurab desert, to give just a few examples. And what about the Island of Flores? Don't stop looking there because it will be another of the eyes of the exciting hurricane that is the science of human evolution.
Now then. Despite all the great discoveries that have been made in the last six years (and, in general, in the last century and a half), the truth is that the big questions (those with which we opened this conference) still remain: Which was the first of the hominids that opened the lineage that would lead to us? How did human beings originate? When, where, and, above all, from which species of pre-human hominid did the human genus arise? Who were the first human beings? Incredible as it may seem to you, this is not clear either and is the subject of a lively discussion. How did our species originate? Where and when did it emerge? From whom did we humans evolve today? And more importantly: What is it to be human? Are we exclusively human beings Materials, or do we have spiritual dimensions? What is the destiny of each individual person and of humanity in general? These and many other such questions * (75) are still waiting for "the" clear answer final.
We must recognise the greatness of the science of human evolution, for every day it provides more and more important data, as we believe we have been able to demonstrate throughout this presentation, for the knowledge of the pathway biological of our evolutionary history. And there is no doubt that in the coming years it will continue to provide knowledge of great importance, as we have pointed out above, for a better understanding of our evolutionary past. But it is also true that there are scientific questions that it is becoming increasingly clear may never be able to resolve. Then, in human evolution, we must strive to distinguish between our circumstantial ignorance (from which we will progressively emerge as new discoveries are made) and our structural ignorance (that which derives from the nature of the topic in question). This should help him to recognise, with humility, his limits. It is evident that its own research methods prevent it from being able to answer (now and always) some of the fundamental questions that every human being asks as a human being; therefore, a distinction must be made between evolutionism as a scientific theory and the ideological use that is made of some of the conclusions reached by the studies at subject on human evolution. This use, and abuse, is entirely spurious to the science of human evolution itself. But the fact that the science of human evolution can never answer them does not mean that humans give up asking these questions and searching for a reasonable answer.
There are scientific questions related to human evolution that one day we will be able to resolve and know their truth with a very high Degree of reliability. There are other questions that, although scientific in nature, we may never be able to know with absolute clarity. And finally, there are other questions related to man, and extremely important for our lives, which by their very nature are beyond what the science of human evolution can provide. Hence it is necessary for us to listen to metaphysics and theology to see what they can really tell us about the fundamental questions that trouble human consciousness.
In our opinion, palaeoanthropology should be reminded that it cannot answer all the questions posed by human beings, and therefore should not look down on metaphysics and theology for the simple fact that they do not reason using the same methods. And they should be reminded that they should not look askance at the science of human evolution, accusing it of being materialistic. It is good for them to keep in mind the data and conclusions (however tentative they may be) provided by this science. They should also remember the words of John Paul II before the Pontifical Academy of Sciences on 22 October 1996, in which he explicitly stated that "the theory of [human] evolution is more than a hypothesis" * (76).
Human beings therefore need the sincere, respectful and honest input and collaboration of all branches of knowledge involved in explaining the most important questions we can ask ourselves as humans about ourselves.
After all that has been said, I would like to thank you for your presence and interest in these topics, as well as for your patience in listening to me. I would also like to thank the University of Navarra for having honoured me with their trust by inviting me to give this lecture on human evolution. Thank you very much to all of you.
Heraclitus of Ephesus 6th and 5th century B.C. (probably -544/-484) is a good example. Thus, according to the testimony of Plutarch, the Ephesian claimed that: "I went about searching for myself" (Fr. 101, Plutarch, adv. Colot. 20, 1118c).
Gamble, Clive: Gibraltar and the Neanderthals 1848-1998 ; Journal of human Evolution, Vol. 36, pp. 239-243, 1999.
A name borrowed from Aldous Huxley, who believed that the missing link must be something intermediate between man and ape and therefore called it: Pithecanthropus; and, naturally, it must not speak (alalus). In this respect, it is worth recalling the words of Ralph L. Holloway: "We will never know whether Australopithecus, Homo erectus, Homo habilis or Neanderthals could speak, unless something is invented that allows us to travel back in time"; Diari Avui, 17 November 2001, p. 34.
The text of his study on the Taung skull and his considerations on Australopithecus africanus were published in the scientific journal Nature. Cf. Raymond A. Dart: Australopithecus africanus: The man-ape of South Africa ; Nature, Vol. 115, no. 2884, pp. 195-199, 7.II.1925.
Although he was first called Zinjanthropus boisei. Zinjanthropus means: "East African man".
Representing the oldest and most numerous hominin group ever found together, group .
Cf. T.D. White, G. Suwa & B. Asfaw: Australopithecus ramidus, a new species of hominid from Aramis, Ethiopia ; Nature, Vol. 371, pp. 306-312, 1994.
M. Brunet et al.: The first australopithecine 2,500 kilometres west of the Rift Valley (Chad) ; Nature, Vol. 378, pp. 233-240; 1995. Cf. also M. Brunet et al.: Australopithecus bahrelghazali, une nouvelle espèce d'Hominidé ancien de la région de Koro Toro (Tchad). C. R. Acad. Sci. Paris , Ser. IIa 322, 907-913, 1996.
Cf. M.G. Leakey, A.C. Walker, C.S. Feibel & I. McDougall: New four-million-year-old hominid species from Kanapoi and Allia Bay, Kenya ; Nature, Vol. 376, pp. 565-571, 1995. Cf. also M.G. Leakey & A.C. Walker: Ancient hominid fossils in Africa; Research and Science, August 1997, pp. 70-75.
M.G. Leakey, A.C. Walker, C.S. Feibel, I. McDougall & C. Mark: New specimens and confirmation of an early age for Australopithecus anamensis ; Nature, Vol. 393, pp. 62-66, 1998.
For a detailed knowledge of the morphology of anamensis see M.G. Leakey, A.C. Walker & C.V. Ward: Morphology of Australopithecus anamensis from Kanapoi and Allia Bay, Kenya ; Journal of Human Evolution 41, 235-368, 2001.
B. Asfaw , T. D. White, O. Lovejoy, G. Suwa et al.: Australopithecus garhi: A new species of early hominid from Ethiopia. Science, 23 April 1999, Vol. 284, no. 5414, pp. 629-635. Cif. Also J. Desmond Clarck, Tim D. White et al.: Envairoment and behavior of 2.5-million-year-old Bouri Hominids; Science, 23 April 1999, Vol. 284, No. 5414, pp. 625-629.
J.M. Bermúdez de Castro, J.L. Arsuaga, E. Carbonell, et. al.: A hominid from the Lower Pleistocene of Atapuerca, Spain: Possible ancestor to neanderthals and modern humans ; Science 276, 30 May 1997, pp. 1392-1395.
Francesco Mallegni, et. al.: Homo cepranensis, sp. Nov. And the evolution of African-European Middle Pleistocene hominids ; Comtes Rendus Palevo, 2003, vol. 2, no. 2, pp. 153-159.
The relationship between afarensis and africanus is the subject of discussion. For some, afarensis is the ancestor of africanus. For others this is impossible and africanus should be the descendant of another species of Australopithecus, e.g. in South Africa, in the Sterkfontein cave, the skeleton of an Australopithecus yet to be determined is being patiently unearthed (Little Foot.). Lee R. Berger (of the University of the Witwatersrand, the same university where Raimond Dart worked) is of the opinion that afarensis cannot be the parent species of africanus, because, although it is true that the skull of afarensis is notoriously more archaic than that of africanus, it is also true that the rest of the postcranial skeleton of this hominid sample has more primitive features than that of the Hadar specimen. Thus both species, Berger argues, must be descended from a common ancestor that had an afarensis-style skull and a postcranial skeleton more similar to that of africanus.
All this may seem normal: theories are proposed, contrasted with the data collected in the excavations and a preferred choice is made, and all of this is done with the utmost normality. But in reality this is not the case. Debates in human palaeontology unleash passions among scientists. And all this to unsuspected extremes for those who are not familiar with this field of science. And the discussion that has been opened around whether afarensis spent more time in the trees or whether it was more bipedal is a good example of what we are saying. Lee R. Berger captures the tense atmosphere surrounding this controversy when he tells us that: "The vehemence that accompanies any discussion about human origins was not absent from this tree-climbing controversy. Indeed, the 1980s and early 1990s were a period of profound disagreement between the two camps, so sharp that interpretation of the function of a single muscle could lead to fierce public clashes between scientists. At lectures, some were excluded from their group for simply addressing a member of the opposing camp. Students like me were plunged into a cold war between men of science who challenged claims that were impossible to prove without a time machine..." (In the footsteps of Eve. The mystery of the origins of humanity. Ediciones B, 2001, p. 195).
Avatars that are, in part, recounted by Declan Butler in his article: The battle of Tugen Hills, Nature 410, 508-509, 29 March 2001.
Technical data published in Brigitte Senut, Martin Pickford, Yves Coppens et al.: First hominid from the Miocene (Lukeino Formation, Kenya) ; Comptes Rendus de l'Académie des Sciences, Paris, series IIa, Sciences de la Terre et des Planètes, no. 322, pp. 137-144, 2001.
Cf. M. Pickford & H. Ishida: A new late Miocene hominoid from Kenya: Samburupithecus kiptalami gen, et sp. nov. ; C. R. Acad. Sci. Paris 325, pp. 823-839, 1998.
A genus of hominids proposed by Weinert in 1950 and which at the end of the nineties of the last century saw some authors (Bernard Wood and Mark Collard, for example) proposing its rehabilitation. According to Pickford and Senut, this genus would be made up of specimens that have so far been poorly catalogued; and would include some fossils erroneously attributed to Australopithecus afarensis, as well as the mandible from Chad assigned by Michel Brunet to Australopithecus bahrelghazali.
In this sense Ron Clarke (researcher of the department of Anthropology and Human Genetics in Frankfurt, Germany, and of the Sterkfontein Research Unit, department of Anatomy of the School of Medicine of the University of the Witwatersrand, Johannesburg, South Africa) states that: "Orrorin tugenensis definitively proves the existence of hominids 6 Ma. ago"; C.R. Clarke: New fossil genera; Scientific World, no. 228, p. 28, 2001.
Yohannes Haile-Selassie: Late Miocene hominids from the Middle Awash, Ethiopia ; Nature, Vol. 412, pp. 178-181, 2001.
Yohannes Haile-Selassie; Gen Suwa & T. D. White 2004: Late Miocene Teeth from Middle Awash, Ethiopia, and Early Hominid Dental Evolution. Science 303: 1503-1505.
Carlos Lorenzo: First hominids. Genera and species. In VV.AA.: Homínidos. Las primeras ocupaciones de los continentes; Ed. Ariel, Barcelona, 2005, p. 108.
M. Brunet, D. Pilbeam, Y. Coppens, L. De Bonis, Marcia Ponce De Leon, Christoph Zollokofer, et alt.: A new hominid from the Upper Miocene of Chad, Central Africa ; Nature, 418, pp 145-151, 11. Cif. Also Carlos A. Marmelada: Descubierto en Chad el posible antepasado más lejano del hombre; Aceprensa, 17 July 2002, Service 103/02.
Cf. Patrick Vignaud et al.: Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature, 418, pp. 152-155, 11.VII.2002.
Chris Stringer: La evolución humana; Ed. Akal, Madrid, 2005, p. 115.
M. Brunet et al.: A new hominid from the Upper Miocene of Chad, Central Africa ; Nature, 418, p. 145.
M. Wolpoff, M. Pickford & B. Senutt: Sahelanthropus or "Sahelpithecus"? Nature, Vol 419, 10 October 2002, pp. 581-582.
Cif. Carlos A. Marmelada: Toumaï: Homínido o mono?; Aceprensa, 23 October 2002, service 138/02.
Brunet et. al. reply: Sahelanthropus or "Sahelpithecus"? Nature, Vol 419, 10 October 2002, p. 582.
M. Brunet et al.: A new hominid from the Upper Miocene of Chad, Central Africa ; Nature, 418, p. 151.
Cf. Henry Gee: Toumaï, face of the deep ; Nature, Vol. 18, 11.
B. Wood: Paleoanthropology: Hominid revelation from Chad ; Nature, Vol. 418, pp. 133-135, 11.
"The discussion is still open, but the species best placed to be considered the first hominid is still Ardipithecus, thanks to its dental morphology, especially its small and incisiviform canine". Carlos Lorenzo: op. cit. p. 109.
"A long time ago (...) some peculiar primates were able to exploit the possibilities of a particular ecological niche (...) The protagonist of this evolutionary achievement, crucial for our phylogenetic history, we consider to be the first member of an evolutionary lineage leading to us (...) This being is known as Orrorin tugenensis". Camilo José de Cela Conde and Francisco Ayala: La piedra que se volvió palabra; Alianza publishing house, Madrid, 2006, pp. 14-15.
Brigitte Senut: La aparición de la familia del hombre; in VV.AA.: Los orígenes de la humanidad. Vol. I, Ed. Espasa, Madrid, 2004, p. 189.
Jordi Agustí and David Lordkipanidze: From Turkana to the Caucasus; National Geographic, RBA, Barcelona, 2005, p. 62.
For a discussion of the impact of all these discoveries on the various phylogenetic proposals see Leslie C. Aiello & Mark Collard: Our newest oldest ancestor? Aiello & Mark Collard: Our newest oldest ancestor?; Nature, Vol. 410, pp. 526-527, 29. Cf. also Daniel E. Lieberman: Another face in our family tree; Nature, Vol. 410, pp. 419-420, 22.III. 2001, who calls Kenyanthropus a "spoiler" for having complicated the hominin family tree, showing that the variability and diversity of the hominin family tree is much greater than hitherto assumed. Cf. also Clarke, Ron: New Fossil Genera; Scientific World, no. 228, pp. 24-28 and Cohen, Claudine: Our Ancestors in the Trees; Scientific World, no. 228, pp. 28-33.
Cf. M. Leakey, F. Spoor et al.: New hominin genus from eastern Africa shows diverse middle Pliocene lineages ; Nature, vol. 410, pp. 433-440, 22.
KNM stands for Kenyan National Museums and WT refers to the geographical area in which finding took place: the west of Lake Turkana in north-western Kenya.
Leo Gabunia, Marie Antoine de Lumley, Abesalom Vekua, David Lordkipanidze, Henry de Lumley: Discovery of a new hominid at Dmanisi (Transcaucasia, Georgia); Comtes Rendus Paleov, September 2002, vol. 1, no. 4, pp. 243-253. Cif. also, Ann Gibbons:Oldest members of Homo sapiens discovered in Africa ; Science, Vol. 300, 13 June 2003, p. 1641.
For more information on Homo gorgicus and all things related to Dmanisi see, for example, Jordi Agustí and David Lordkipanidze: From Turkana to the Caucasus ; Leo Gabunia, Abesalom Vekua, David Lordkipanidze, Carl C. Swisher, Marie-Antoinette de Lumley, et al. Swisher, Marie-Antoinette de Lumley, et al.: Earliest Pleistocene Hominid Cranial Remains from Dmanisi, Republic of Georgia: Taxonomy, Geological setting, and Age ; Science 2000, May 12; 288: 1019-1025. Abesalom Vekua, David Lordkipanidze, Jordi Agustí, Marcia Ponce de León, Christoph Zollikofer, et al.: A new skull of early Homo from Dmanisi, Georgia ; Science 2002, July 5, 297: 85-89.
Cif. T. D White, B. Asfaw, G. Suwa et al.: Pleistocene Hom sapiens from Midle Awash, Ethiopia ; Nature, Vol. 423, 12 June 2003, pp. 742-747. For some of the reactions to Homo sapiens idaltu among experts see Chris Stringer: Out of Ethiopia; Nature, Vol. 423, pp. 692-695, 12 June 2003; Ann Gibbons: Oldest member of Homo sapiens discovered in Africa; Science, Vol. 300, p. 141, 13 June 2003; Sarah Graham: Skulls of Homo sapiens recovered; Scientific American Digital(http://www.sciam.com). On the official website of the University of Berkeley(http://www.berkeley.edu/news/average/releases) you can find videos recorded on site, photos, interviews with Tim D. White, articles giving scientific details and anecdotes related to the findings.
J. Desmond Clark et al.: Stratigraphic, chronological and behavioral context of Pleistocene Homo sapiens from Middle Awash, Ethiopia; Nature, Vol. 423, 12 June 2003, p. 747 et seq. And William K. Hart: Geochronology (communication arising): Dating of the Herto hominin fossils ; Nature, Vol. 426, 11 December 2003, p. 622 et seq.
an McDougall, Francis Brown and John Fleage, Stratigraphic placement and age of modern humans from Kibish, Nature 433, 17 February 2005, pp. 733-736.
Christopher Henshelwood et al.: Emergence of modern human behaviour: Middle Stone Age engravings from South Africa , Science 295 (February 2002), p. 1279. On the emergence of modern human behaviour, cf. Carlos A. Marmelada: El origen de la conducta humana moderna ; Aceprensa, 11 September 2002, Service 117/02.
P. Brown, M.J. Morwood, et. al.: A new small-bodied hominin from thelate Pleistocene of Flores, Indonesia ; Nature, 431, 28 October 2004, pp. 1055-1061. Cf. also Marta Mirazón and Robert Foley: Human evolution writ small; Nature 431, 28 October 2004, pp. 1043-1044. For knowledge of the archaeological context and dating of the site see M.J. Morwood, R.G. Roberts, et. al.: Archaeology and age of a new hominin from Flores in eastern Indonesia; Nature 431, 28 October 2004, pp. 1087-1091.
D. Falk, Ch. Hildebolt, M. Morwood, P. Brown, et. al.: The brain of LB1, Homo floresiensis ; Science Express, 3 March 2005. Cf. also, Michael Balter: Small but smart? Flores hominid shows signs of advanced brain ; Science 307, 4 March 2005, pp. 1386-1389.
Data calculated from a virtual reconstruction of the skull using computed tomography (CT) techniques.
View expressed by Groves in Larry Barham: Some initial informal reactions to publication of the discovery of Homo floresiensis and replies from Brown & Morwood ; in Before Farming 2004/4 article 1, p. 2.
Morwood and Brown's reply to Groves in Larry Barham: Some initial informal reactions to publication of the discovery of Homo floresiensis and reptils from Brown & Morwood ; Before Farming 2004/4 article 1, p. 5.
"Bones of contention" is a phrase that is becoming common currency in the world of human palaeontology.
"There is no a priori reason to think that australopithecines (or even H. habilis -shouldn't it be the other way around? grade of the author-) did not colonise other continents. But if Australopithecus left Africa and survived in Flores until recently, we would have to ask ourselves why more fossils do not appear to support this hypothesis. According to Wolpoff, these may already have been found. In the forties of the last century a set of remains were found in Indonesia which have been classified by several authors as Australopithecus, Meganthropus and, more recently, H. erectus. They should now be re-examined in the light of the new human fossils from Flores" (Kate Wong: The Flores Man; Research and Science, April 2005, no. 342, p. 28).
R. D. Martin et al.: Comment on "The brian of LB1. Homo floresiensis"; Nature, Vol. 312, 19 May 2006, p. 999b.
Anthropologists walk tall after unearthing hominid ; Nature 434, 10 March 2005, p. 126. Something similar can be seen in Science; cf. Ann Gibbons: Skeleton of upright human ancestor discovered in Ethiopia ; Science 307, 11 March 2005.
T.D. White, B. Asfaw, G. Suwa, Y Haile-Selassie, Elisabeth S. Vrba, C. Owen Lovejoy, et al.: Assa Isse, Aramis and the origin of the Australopithecus ; Nature, Vol. 440, 13 April 2006, pp. 883-889.
William H. Kimbel, Meave Leakey, Donald C. Johanson: Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record ; Journal of human evolution, Vol. 51, issue 2, August 2006, pp. 134-152.
Lee R. Berger: In the Footsteps of Eve; Ediciones B, Madrid, 2001, p. 222.
Cif. Carlos A. Marmelada: Is Pierolapitheucs catalaunicus the missing link?; Aceprensa, 15 December 2004, Service 161/04.
Cif. Carlos A. Marmelada: Los neandertales no son antepasados nuestros; Aceprensa, 14 June 2006, Service 068/06.
Camilo José de Cela Conde and Francisco Ayala: Senderos de la evolución humana; Alianza publishing house, Madrid, 2001, p. 418.
Cann, R. L.; Stoneking, M. and Wilson, A. C.: Mitochondrial DNA and human evolution ; Nature, 325, 31-36, 1987.
Krings, Matthias; Pääbo, Svante et al.: Neandertal DNA Sequences and the Origin of Modern Human ; Cell, 90, 19-30, 1997.
Krings, M.; Pääbo, S. et al.: DNA sequencing of the mitochondrial hyper variable region II from the Neanedertal type specimen ; Pro. Natl. Acad. Sci., Vol 96, pp. 5581-5585, May 1999.
Ovchinnikov, Igor V. et al.: Molecular analysis of Neanderthal DNA from the northern Caucasus; Nature, 404, 30 March 2000, pp. 490-493. Cif also Höss, Matthias: Ancient DNA: Neanderthal population genetics ; Nature 404, 30 March 2000, pp. 453-454.
Krings, Matthias; Pääbo, Svante et al.: A view of Neanderthal genetic diversity ; Nature genetics, Vol. 26, October 2000, pp. 144-146.
Lalueza Fox, Carlos; Bertranpetit, Jaume; Rosas, Antonio et al.: Neanderthal Evolutionary Genetics: Mitochondrial DNA data from the Iberian Peninsula. Molecular Biology and Evolution vol. 22, 2 February 2005, pp. 1077-181.
Cela Conde, Camilo José de and Ayala, Francisco: Op. cit.; p. 431.
Stoneking, Mark and Pakenford, Brigitte: Mitochondrial DNA and human Evolution ; Annual Review Genomics Human Genetics; Vol. 6, pp. 165-183, 2005.
Cif. Carlos A. Marmelada: Luces y sombras en el estudio de la evolución humana; Universidad de Navarra,http://www.unav.es/cryf/lucesysombras.html.
John Paul II, Message to the Pontifical Academy of Sciences; 22 October 1996, n. 4: in L'Osservatore Romano, edition in Spanish, 25 October 1996, p. 5.