Homo floresiensis. The great little mystery of human evolution

Author: Carlos A. Marmelada
lecture pronounced at: Cardenal Herrera University, Valencia
Date of publication: 19 April 2005

Introduction

The finding of a new human species that must have become extinct, at the latest, around 12,500 years ago (12.5 Kyr.) and, therefore, coeval with our own, with a little over a metre in height, a brain of a size analogous to that of the australopithecines of between three and four million years ago, and scarcely larger than that of today's chimpanzees, has been considered the most important finding of the last fifty years in the field of human palaeontology. Science magazine even ranked it as the most important scientific finding of 2004.

Palaeoanthropology is a branch of science that has the good fortune or misfortune to see how each of its major discoveries generates more questions than answers* (1). It opens more doors than it closes. The case of Homo floresiensis is not an exception. Sometimes this fact reaches limits bordering on paroxysm: human palaeontology is the branch of science in which it is more frequent to see how once or twice a year an important finding is presented by its discoverers as a revolutionary fact that forces to restructure all the elements that make up the building of this science. In no other branch of scientific knowledge is a paradigm shift, or at least a serious restructuring of the existing paradigm, proposed so frequently* (2).

The most ill-intentioned minds may think that, in the uphill struggle for a share of the scarce funds for research in this field, the most spectacular and revolutionary projects have a better chance of getting a share of the cake. We are of the opinion that the real causes must lie elsewhere. Let's look at it.

Although the first human fossils were discovered in 1830, palaeoanthropology is a very young science. In fact, at that date, the Belgian anatomist Phillip Charles Schmerling found three skulls in the Belgian cave of Engis; the first was very deteriorated, the second belonged to an anatomically modern human (i.e. someone of our species), but the third is that of a Neanderthal child. In 1848, during fortification work on the Rock of Gibraltar, another fairly complete Neanderthal skull was discovered at Forbes Quarry. However, in neither case were these fossils recognised as human remains belonging to a species other than our own and now extinct. This event did not occur until 1864, when William King (Professor at Queen's College, Galway, Ireland) proposed to include the fossilised remains found in 1856 in the Feldhofer cave, 20 metres above the river Düssel, in the Neander valley (this is precisely the literal meaning of the word "neander-tal"), near the German city of Düsseldorf, in a new human species, which he called: Homo neanderthalensis. Then in 1868 the remains of direct ancestors of ours were discovered with a little more than 30 Kyr, the so-called "Cro Magnon Man". In 1891 the Dutch doctor Eugen Dubois discovered in Java human remains that were more than one million years old and that nowadays are assigned to Homo erectus, which, for the time being, is one of the main candidates for the direct ancestor of Homo floresiensis.

Although since then, fortunately, there have been many discoveries, some of them really important, the truth is that we still have a lot to know. Unfortunately, we cannot share the triumphalist views that proclaim that the essentials of human evolution have been discovered and that only small details remain to be worked out. According to this way of interpreting the current state of our knowledge on subject of human evolution, it would seem that the edifice of our knowledge in this field would be practically finished, all that remains to be done is to put a framework on that door, an embossed fence on that window, and a few more coats of paint here and there.

Frankly, we would like this to be the case, but, as we have already said, we see status differently. It is true that we know so much more today than we did only a few years ago. In just a decade, new discoveries have been made:

a.- Four new hominid genera with their respective species: Sahelanthropus tchadensis*(3), Orrorin tugenensis*(4),Ardipithecus*(5)ramidus kadabba* (6)and A. ramidus ramidus ramidus and Kenyanthropus platyops*(7)).

b.- Three new species of Australopithecus: A. anamensis*(8), A. bahrelghazali*(9)and A. garhi*(10).

c.- Four new human species: Homo georgicus* (11), H. cepranensis*(12), H. antecessor*(13) and H. floresiensis* (14).

d.- And a subspecies of our species: Homo sapiens idaltu*(15).

In addition to this, there have been numerous finds of hominin remains assignable to already known genera and species, but also a large number of remains not yet assigned to any genus and species; for example, early last March Yohannes Haile-Selassie announced that his team had found hominin remains 4 million years old (4 Ma.) old hominid remains that were already bipedal, but cannot yet be assigned to any genus or species*(16); the same goes for "Big Foot", fossil remains more than 3 Ma. old found by Ron Clarke in Sterkfontein, South Africa, last decade.

It is true that the fossil record, always very meagre* (17), has recently become much fatter; and, fortunately, it looks set to become much fatter in the very near future. But it is also true that the questions core topic remain unanswered, without a satisfactory answer. Thus, we still do not know which was the Miocene hominoid that gave rise to the hominid family, i.e. we do not know who was the last common ancestor of hominids, panids and gorillids*(18), nor which was the first hominid that opened the path that would lead to our lineage. Nor do we know which pre-human hominid gave rise to our genus* (19). It is not even entirely clear who the first humans were* (20); indeed, palaeoanthropologists are finding it increasingly difficult to define what is man? This is just one button sample of the problems we have in relation to phylogenies*(21); but the difficulties are no less in other matters: we thus have only a highly hypothetical sketch of the emergence of human consciousness in general and modern human consciousness in particular. We do not know who were the first humans to speak, nor when they began to do so; moreover, we will never know what their mental Structures were, that is, we will never know what was the symbolic universe that flowed through their minds. Not only do we not know how our genus emerged (sit venia verbo), but it is also unclear from where our species emerged* (22). We could go on listing many other important questions that are still awaiting not only a solution to the enigma, but at least a satisfactory answer (when did bipedalism emerge and what was its cause? Who was the maker of the first tools? etc.).

The cause of all this? H. Vallois was able to explain it clearly when he stated that reconstructing human phylogeny from the fossil record we have is a bit like trying to reconstruct the plan of Paris from the protruding towers of a flood that would have inundated it all. We liked to use the example of the jigsaw puzzle, until three years ago, when we found it explained by Jean Chalin, to whom we therefore gladly cede the floor: "Imagine," says the French palaeontologist, "that we embark on an operation to put together a puzzle of more than a million pieces of which we only have between 150 and 200, and that we ignore the details of the final drawing for which we only have a few points from reference letter in the upper part of the puzzle, that is, from the current data (...)...) That is the goal of palaeontologists"* (23). No comment is necessary.

Although human palaeontology has almost a century and a half of factual existence, as a science in the strict sense of the term it is much younger. Only in the last few decades has it been making explicit the methodological elements that have allowed it to grow as a fully-fledged empiriometric science. Perhaps in this relative youth lies one of the keys to understanding the incessant convulsions that its paradigm undergoes every year. It is very striking to see how, in this branch of science, almost every major finding forces us to rethink everything. In palaeoanthropology, the outline described by Thomas S. Khun in his work The Structure of Scientific Revolutions does not seem to apply. Here, there have never been long periods of calm in which the paradigm has lived peacefully in the quiet lap of the academic community, those periods which Khun calls "normal science". In this branch of scientific knowledge the paradigm has always been the subject of a lively and heated discussion.

Then we will see: where, when and how Homo floresiensis was discovered: the last great milestone that forces us to rethink the history of the human evolution, as we understood it until now. Then we will see its morphological characteristics (what it was like); its ecology (how it lived); what lithic industries it made (its technology); what its intellectual capacities might have been; the problem posed by its origin and evolution; the controversy surrounding the custody and study of its remains, as well as their interpretation. We will also have to pay close attention to result of the genetic programs of study which has already been commissioned. Finally, what other surprises may the future of palaeoanthropological research in this geographical area hold for us: will there be other human species other than ours and floresiensis waiting to be discovered? Alexander Koyré defined the Renaissance as the time when everything was possible: mutatis mutandis, it seems that, from the finding of Homo floresiensis, we can say the same about the human evolution. Or at least we have to recognise that this finding has to open our minds and make us aware that most probably there are still many surprises to be discovered in human palaeontology, some of which will undoubtedly be linked to Homo floresiensis.

1.-Location of the Island of Flores

Flores is a small tropical island in the Indonesian archipelago. To the west are the islands of Java and Bali, to the northwest Borneo, to the north the Celebes (Sulawesi), to the southeast Timor and to the south Australia.

It is approximately 360 km long and ranges in width from a maximum of 60 km (in the western part) to less than 20 km in parts of the eastern part. At 14,000 km2 Flores is almost three times the size of the Balearic Islands.

To the west of Flores is the island of Comodo, famous for the largest reptiles in the world: the Commodus Dragon, which was apparently part of the per diem expenses of Homo floresiensis.

2.- The finding and its publication

In October 2004 Flores became world famous when it was announced that the skeleton of a human being measuring just over one metre had been discovered there. It was the remains of a woman who had died as an adult, having died some 18,000 years ago (18 Kyr). The surprising thing is that her size and her physical features seemed to justify assigning her to a new, hitherto unknown human species: Homo floresiensis. To make matters worse, it turned out that her brain did not exceed the size of a chimpanzee; moreover, her remains had appeared in the same stratum in which thousands of lithic tools were found, with a level of development similar to what they had reached among other humans, such as the Neanderthals or the Sapiens.

Each of the above-mentioned elements alone presents a whole challenge for the scientific research . The universal media impact was therefore more than justified. From a scientific point of view, the news was truly unbelievable. If a paleoanthropologist had wanted to play a joke on a colleague on 28 December, it simply would not have stuck; no one would have believed such a thing.

But it was no joke. The advertisement of such a fabulous finding was published in the prestigious journal Nature. The articles concerning the finding had passed the sieve of a rigorous committee of experts and had the nihil obstat of the prestigious archaeologist Christopher Stringer. A magazine that puts its reputation on the line, week in, week out, cannot risk publishing speculative nonsense. The finding of the existence of a new human species that had been contemporary to us and had recently become extinct was serious.

The finding had been made in September 2003, when a team of research led by: Mike Morwood and Peter Brown (both from the University of New England, Armidale, Australia) found in sector VII of Liang Bua cave the skull and part of the postcranial skeleton of an individual belonging to a new human species.

3.- Location of the finding

Liang Bua is a karst cave located in the centre of the western part of the island, about 14 km northwest of Ruteng, the capital of Manggarai department ; and about 25 km from the northern coast, washed by the Flores Sea. It is 500 metres above sea level, and its training is due to the action of the Wae Racong River, which is now about 200 metres away from the cave and 30 metres below the level of the cave.

Sector VII is the place where the skeletal remains of Hobbit (affectionate nickname with which her discoverers have decided to name this female of Homo floresiensis, due to her short stature* (24)) have been found. It is a small area of 4 m2 located very close to the eastern wall. The skeleton was found at a depth of almost six metres (5.9 m.), in a very small area: approximately 500 cm2 (20x30 cm). Animal remains and stone tools were found at the same level. Dated by the carbon-14 method, the upper layers of this level date to between 11 and 13 Kyr.

At first, its discoverers thought they had stumbled upon the skeleton of a child. But when they analysed the teeth, they were able to see that the wear and tear was consistent with the longevity of an adult. Judging by the shape of the pelvis, it seems that the skeleton was that of a woman who may have died at the age of 30.

If it was not a boy, then could it be a pygmy subject of our species? The authors of the finding discard this hypothesis, arguing that the short stature of pygmies is due to the fact that their body growth stops just at the beginning of adolescence, but the brain has already finished its normal growth rate, so it is already the size it will be when the individual is an adult. That is to say: a pygmy sapiens is very tall leave but has a brain with the average volume of our species and, therefore, with a much higher rate of encephalisation than that of floresiensis.

Nor are we looking at a female with growth anomalies, as isolated remains have been found from other individuals that point in the same direction: small size as a specific characteristic and not as a sign of a growth anomaly.

Despite their diminutive size, they hunted animals such as extinct dwarf elephants (Stegodon), mainly their young; giant lizards, the famed Comodo dragon (still extant), snakes, turtles, frogs, rodents and bats. Since the bones of some of these animals have been found charred, it is believed that floresiensis must have mastered fire.

Thousands of lithic tools used for skinning, butchering, tanning or drilling have also been found at Liang Bua. Many of these tools appear in sediments that are 78 Kyr old. We know that sapiens did not arrive in Flores until about 12 Kyr ago. Who is the author of these tools from Flores, so similar to those made by the Neanderthals in Europe and the sapiens in Africa at that time? We still do not know for sure.

Shortly after her death, her body was covered by a thin layer of sediments. Radiocarbon and luminescence dating methods have been used to determine the age of these sediments in order to infer the exact dating of this hominid's remains. Two samples of the skeleton were dated by carbon-14 and both yielded a similar result : 18 Kyr.

In sector IV, a premolar was found with the same morphological characteristics as those found in the complete mandible of the hominid from sector VII (Hobbit), and has therefore been assigned to the same species; it is also attributed an age of 18 Kyr. Below this premolar, a molar belonging to a young individual of Stegodon has been found which, dated by thermoluminescence, gives an approximate age of 74 Kyr.

Even more ancient are the skeletal remains of a hominid that could be around 95 Kyr. In any case, no less than 74 Kyr. The remains include a radius of an adult individual who must also have been about a metre long. This stature is what has made them to be provisionally assigned to Homo floresiensis, while awaiting the realization of programs of study that can further specify or confirm their specific assignment.

What were Hobbit's intellectual capacities? After a lively controversy, to which we will refer later, his discoverers, in partnership with the palaeoanthropologist Dean Falk and the radiologist Charles Hildebolt, have carried out a study of the LB1 skull, which was published at the beginning of March*(25). When Hobbit was presented to society in October 2004, it was estimated to have a brain volume of 380 cc, identical to the average volume of today's chimpanzees, and a far cry from the 1350 cc of today's humans. The new volume attributed now to the brain of floresiensis is 417 cc. * (26), a figure that includes it within the characteristic parameters of the gracile Australopithecus, subject Lucy, 3 million years ago. However, what most caught Falk's attention was not so much the volume as the structure of the brain: a cranial size typical of an australopithecus but with a clearly human brain structure. Y... how can we know this? The brain does not fossilise, but it 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: a.- it had highly developed temporal lobes (areas that in our genus are associated with language comprehension, in them we find Wernicke's area and Broca's area ), and the cerebral area that controls hearing and b.- the frontal lobe (area associated with the control of rational abilities and planning for the future) is also highly developed. These data allow us to speculate on 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 * (27)(a possibility also considered by Falk*(28), Morwood, Brown*(29)and others*(30)). Of course, if this is the case, 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"* (31). Giants of human palaeontology, such as Tim D. White and Chris Stringer also disagree with Jacob's interpretation. The controversy has even reached issues such as custody and access to the fossils. Until now they had been in the hands of Jacob (Dean of palaeoanthropology 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 once again at his disposal for their study. Of course, Homo floresiensis is going to give a lot to talk about in the near future, as its semi-fossilised remains have become, for several reasons, some real "bones of discord", as we will be able to see a little further on.

4.- How did Homo floresiensis arise?

One of the great enigmas surrounding this hominid is how its species arose. For the moment, its discoverers suppose that it must have originated from Homo erectus. It is not for nothing that this human species was discovered in Java at the end of the 19th century by the Dutch doctor Eugen Dubois.

In 1887 he set off for Indonesia to find fossil evidence that would prove Darwin right. In 1859, Darwin had published his famous work, The Origin of Species, in which he claimed that present-day living things came by evolution from earlier ones, and these from others, until they were traced back to a first living thing from which all living things that had ever existed descended. The mechanism by which this phenomenon took place, the engine of evolution, was the natural selection of mutations which, arising at random, favoured adaptation to the environment and, therefore, survival. Dubois was born a year before the publication of Darwin's work and grew up in the midst of all the controversy raised by his thesis , especially when applied to our species, after the publication in 1883 of The Origin of Man. In this work Darwin argued that we were no exception in nature; that is, that man also came about by biological evolution from other animal forms and by the same mechanisms (natural selection of random genetic mutations). All the qualities that defined man as such had emerged, progressively, from his purely biological evolution. The then famous German biologist Ernst Haeckel, a fervent supporter of Darwin's thesis , deduced that there must be an intermediate form between present-day man and the primates, which would undoubtedly be the missing link postulated by Darwin. Haeckel called this intermediate form Pithecanthropus alalus ("Speechless ape-man").

As mentioned above, Dubois travelled to Indonesia in 1887 to find this missing link*(32). After several years of work , fortune finally smiled on him in 1891. On a terrace of the Solo River near the village of Trinil, he found a calotte (the cranial vault), a femur and a molar. The femur's unmistakable signs of bipedal gait led Dubois to assign it to a new species: Homo erectus. Controversy rages over the age of these fossils. Originally it was thought that they were about 1.2 million years old; they could even be as old as 1.4 million. But in the 1990s, geochronologists Carl Shiwsher and Garniss Curtis assigned much older ages to the fossils than previously assumed. They claim that the Trinil remains could be astonishingly old as 1.8 million years. But many scientists are sceptical of the latter date and claim that there may have been stratigraphic contamination of the sediments. More controversial are the dates of their extinction, which, according to Shiwsher, would be as old as 30,000 years. If they were true, they would turn the erectus of Java into contemporaries of the sapiens and floresiensis.

In principle, it is reasonable to assume that Homo floresiensis comes from Homo erectus. The assumption is based on a number of shared traits, but also on the fact that erectus is the only ancestral species we have documented in the fossil record from that area.

On the other hand, there are those who claim to see more resemblance with Homo habilis. In fact, Homo floresiensis shows traits of a mosaic evolution: together with derived characters it preserves other shared ones; among its anatomical traits there are some that, indeed, evoke H. habilis (for example the stature) or even Homo georgicus (a human species named after the remains found in Dmanisi, Georgia). Such is the view of Juan Luis Arsuaga, one of the three famed co-directors of the popular Atapuerca palaeoanthropological sites in Burgos. But it is also the view of Colin Groves of the Australian National University in Canberra*(33). Even Morwood and Brown, in their reply to Groves admit that they consider the possibility that floresiensis could derive from a human form previous to erectus; maybe Homo habilis; even some human species, not yet found, and which had already reduced its size in a state of isolation in other small islands. Both options are tremendously revolutionary and in the absence of conclusive evidence it is best to opt for a conservative position: Homo erectus was present in Java 1.8 Ma. ago, so it had more than enough time to reach Flores, in one way or another, and evolve there into the human species we are discussing.

What would happen if Homo floresiensis descended from Homo habilis or Homo georgicus? Quite simply: a large part of the history of human evolution would have to be rewritten, changing many concepts of the classical paradigm, for example: that Homo habilis had never left Africa. This idea begins to be questioned from the moment it is recognised that the remains from Dmanisi are more similar to habilis, although not identical, than to Homo ergaster or erectus; so it has been decided to assign them to a new species: Homo georgicus. We must stop to discuss, even very briefly, the case of the Dmanisi fossils, since it is not totally ruled out that they may be related to the Flores fossils.

In 1991 the team of Leo Gabunia, Abesalom Vekua and David Lordkipanidze happened to find a series of human remains in the Georgian town of Dmanisi. It was estimated to be as old as 1.8 Ma., a truly spectacular discovery that was greeted with great scepticism at the time, as the first humans to leave Africa were assumed to have left much later. The site at Tel Ubeidiya (Israel) yields maximum dates close to 1.4 million years old, the same date that was then attributed to the Indonesian sites of Modjokerto, Trinil and Solo.

The Dmanisi remains were initially attributed to either Homo ergaster or Homo erectus. But in 1999, two new skulls were discovered that forced the question to be reconsidered. The small volume of the skulls, as well as other archaic features, suggested that these human remains did not belong to ergaster or erectus, but were more reminiscent of habilis, although they were not completely identical, as they showed some more modern features not detected in habilis. Therefore, the Georgian team of scientists opted to include it in a new human species: Homo georgicus.

It need not be impossible that habilis left Africa and along the way evolved into georgicus; in fact it is a matter of advancing the outline which proposed that ergaster was the first human to leave Africa, giving rise to the erectus clade during its migration through the Near East. That would be a lot, but to suppose that Habilis or georgicus reached Java and there evolved into floresiensis, or that they sailed to Flores to give rise to that species on that island, is something for which we are not yet mentally prepared, let alone to accept that it was Australopithecus who made such a journey, as Kate Wong suggests, alluding to Milford Wolpoff*(34). Let us leave aside, for the moment, this hypothesis, although, from what we are seeing, in human evolution we cannot close our minds to anything that makes sense.

Let us focus on the hypothesis that, for the moment, seems most plausible. Attribute an arbitrary age of 20 years to each generation and assume that a generation moves an average of 20 km. This would give us a rate of movement of one kilometre per year for these human groups. This means that in less than 40,000 years, Ergaster people starting a migratory movement from Kenya or Ethiopia could have reached any part of Southeast Asia or the Chinese coast, after leaving Africa through the Palestine corridor and skirting the Red Sea and Persian Gulf along the coast of the Arabian Peninsula, and continuing along the Indian coastline to Southeast Asia and Java, which at certain periods has been joined with Indochina and Malaysia to form the Sunda Peninsula.

It is therefore perfectly plausible that Homo ergaster left Africa 1.8 Ma ago, and shortly afterwards, from the point of view of geological time, was already in present-day western Indonesia. If Carl Shiwsher's dating is correct, this hypothesis would be corroborated by empirical data. In any case, Homo erectus was already in present-day Java more than a million years ago.

Did Homo erectus colonise the island of Flores? If so, when did he do it? In 1999, Morwood and Brown's team unveiled to the world finding stone tools that could be 840,000 years old. The authors argue that they are of anthropogenic origin, which means that humans could have inhabited these lands by that date. Some experts advise caution before ruling out the possibility that their origin is due to purely natural causes, i.e. the action of meteorological agents rather than intentional human manipulation.

Let's suppose they really are stones carved by humans. Who made them? Until now it has been assumed that it would have been theerectus; but, in view of what we have seen, we cannot close the door to new surprises related to these dates. However, the authorship of the morphology of these stones is not the only admirable thing in this case. If humans were responsible for the carving of these artefacts, how were they able to reach Flores 840 Kyr ago if it seems that the island was never connected by an arm of land to the mainland?

When the Earth's climate cools, water tends to freeze and concentrate at the poles. Then the sea level leave and many continental shelf lands emerge. Some islands are joined to the continent by arms of land. Although the morphological configuration of the continents has not essentially changed in the last hundred thousand years, the land space potentially habitable by humans has; many regions now covered by water since the end of the last ice age have been emerged for millennia. The same was true almost a million years ago. At times, the sea level was as much as a hundred metres lower than it is today. There are numerous striking examples of this phenomenon: many of the islands that today form the Indonesian archipelago have been joined to the Asian mainland to form the Sunda Peninsula; Australia, New Guinea and Tasmania have been joined to form a single continent: Sahul; and Alaska and Siberia were linked by an arm of land called Beringia, right where the Bering Strait is today. But Flores seems never to have been linked to the Sunda Peninsula. Indeed, it remained beyond the visual horizon.

The great naturalist Alfred Russell Wallace, co-discoverer with Darwin of the theory of evolution by natural selection of randomly acquired characters, spent several years in the East Indies, then under Dutch political control, studying the boundary between two of the three great zones into which the faunas of terrestrial vertebrates are geographically divided. These two kingdoms are: the Arctogea (including Eurasia, Africa and North America) and the Notogea (including Australia, New Guinea and Tasmania). The third kingdom is the Neogene and includes South and Central America. In 1863 Wallace drew the natural boundary between the Arctogea and Notogea to the east of the islands of Mindanao (in the Philippines), Borneo and Bali. Thus, Sulawesi (or Celebes), the Moluccas, the smaller Sunda Islands and Timor were on the Notogean side. Thomas Henry Huxley, famous, among other things, as Darwin's great apologist, named this biogeographical divide after him: the "Wallace Line". Later scholars, however, pushed the line further and further east. There are no impenetrable geographical barriers, so the boundaries between the various biogeographic regions are always blurred and often overlap. To the west of Wallace's Line is the Sound shelf, and to the east the Sahul shelf. Crossing the Wallace Line is only possible in two ways: flying or sailing, either by chance or intentionally. The key questions are, then, who were the first humans to reach Flores? And when did they do so?

Let us continue assuming that the stones found by Morwood and Brown's team are lithic tools carved by men who lived on Flores 840,000 years ago (as they are not associated with bone remains we cannot attribute them to any specific species, although, for the moment, the best candidate is Homo erectus), this would obviously mean that the island was already populated at that time. The question, therefore, would now be, how did they manage to get there?

There are two hypotheses: navigation of fortune and intentional navigation. Although the exact origin of the primates of the New World is not known, some palaeontologists believe that they must have arisen from African congeners that crossed the Atlantic during the Oligocene period thanks to fortunate navigation. Although South America and Africa were then separated by 3,000 km, there are fossilised remains of rodents on both sides of the ocean that are so similar that researchers do not hesitate to link them, claiming that they managed to cross that great distance by chance, perhaps covering the route via islands.

But if it is already remarkable that Australia's first settlers sailed there 60,000 years ago at the latest, it is even more spectacular to suppose that the authors of those tools sailed to Flores 840,000 years ago!

If navigation was intentional, a minimum of shipbuilding and navigation techniques should have been mastered, however rudimentary they may have been. That the erectus, or any other human species of those times, had sufficient knowledge for the construction of some subject boat, however elementary it was, and of the minimum technique to navigate with an intention behind a deliberate goal , is something so exceptional that it is almost unbelievable; not even in the case that in that colonisation the technique of "frog-jumping" was used, that is: moving from islet to islet and from island to island, until arriving to Flores from Java. Between Bali, which was linked to the Sonda Peninsula, and Flores there are two relatively large islands: Lombok and Sumbawa, and other smaller ones, among them: Comodo. Although the distances from one to the other are not very great, many are beyond visual range. Therefore, even assuming erectus was able to navigate, how could he have known that by going out to sea he would find land? We can think of two reasons why he might suspect that not far from the farthest point his sight could reach there might be land:

1. The migratory flight of birds. Although we now know that they are capable of flying for hundreds of kilometres without resting, the first humans who supposedly sailed across Wallace's Line may have taken a very risky decision with a fortunate ending without being fully aware of the dangers involved.

2. Another option that might have awakened them to the belief that there was land signature beyond the horizon may have come from observing the plumes of smoke rising from some spectacular fire. A few years ago, a devastating fire in Indonesia was infamous for raising huge plumes of smoke, visible for hundreds of kilometres.

Whether fortunately or more or less deliberately, it is remarkable that just over 800,000 years ago there were already humans on the island of Flores. test Since no human fossils have been found from that time, the indirect evidence that the island was already inhabited by members of our genus is provided by the lithic industry mentioned above reference letter . Let us suppose that, indeed, they are stones carved by humans: what happened then with the population that was confined in the island? What was their evolution along the hundreds of thousands of years that passed from this supposed date of arrival until the extinction of the Homo floresiensis 12,000 years ago? *(35) Did the human species which arrived in Flores and, supposedly, gave rise, with time, to the Homo floresiensis, occupy other islands where they also evolved towards this same human morphology? Perhaps they did it towards other forms?

Why is the physical build of Homo floresiensis so small? Flores is a relatively 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 make a better management use of food resources by making better use of them, thus making their viability possible.

Spectacular cases of body volume reduction have been reported in situations of geographical isolation on small islands. In Sicily, for example, adult elephants averaged as little as 250 kg. Fossilised remains of hippopotamuses weighing 400 kg have been found in Cyprus and Malta. On other Mediterranean islands, fossils of deer the size of dogs have been found.

However, explaining Hobbit's reduction in brain volume is much more complex and less well documented in the fossil record. Palaeontologist Salvador Moyá, from the Institut Miquel Crusafont de Sabadell in Barcelona, found fossilised remains of Myotragos, a species of ox that had reduced the size of its brain by half* in the Balearic Islands (36). Explaining the reduction of brain volume in humans is extremely complex, since it is a predator (although it is possible that lions and hyenas, which are also predators, have reduced their brain volume by a third in the last 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? According to its discoverers, the two most plausible hypotheses are: On the one hand, that Floresiensis are the descendants of a population of Erectus that was confined to the island and drastically reduced its size in order to survive. But, on the other hand, the idea is gaining strength that floresiensis is the descendant of a population of pre-erectus (habilis, georgicus, or -perhaps- another species still to be discovered?) that arrived to Flores much longer ago than imagined until now and, therefore, they arrived already with a small body and brain size, without a process of reduction too significant. We have to remember that Homo habilis measured little more than one metre and its brain is around 600 cm3. Regarding these parameters, those of floresiensis are not particularly distant. Of course, if we compare him with the 1000 cm3 of endocranial capacity of erectus, the reduction of his brain is spectacular. Which of the two hypotheses is the correct one? Time will tell. Is there a third alternative? We shall see.

5.- The bones of discord

Following the publication of the spectacular finding a nasty controversy broke out. Teuko Jacob, the leading Indonesian authority on subject on human evolution, was outside the research, but through a colleague who was part of the team working at Liang Bua he was able to gain access to the Hobbit skeleton. Initially it was to be for a limited time, but nervousness and suspicions began to grow when he missed the successive submission deadlines to which he had committed himself. The protests of the Morwood and Brown team grew because even they could not access the research of the remains they had discovered. The exchange of reproaches was really serious*(37). Jacob was even accused of having kidnapped Hobbit's remains. Besides, the latter did not cease to maintain that the female floresiensis found was nothing more than a member of our species suffering from a growth anomaly, explaining the diminutive size of the brain by a microcephaly, something that Morwood and Brown rejected, with good judgement, out of hand.

Finally, in early March 2005, Jacob returned the Hobbit remains to his discoverers. But their surprise was great when they realised that their worst suspicions had been realised: the Teuko team's handling of the semi-fossilised remains of the female Florfloresiensis had been badly damaged*(38): the pelvis had split; the mandible was missing an incisor; the lower part of the mandible had fragmented in several places (the reconstruction had necessarily changed the physiognomy of this maxillary area); the upper rear part of the mandible was missing a fragment of bone; an empty space, previously non-existent, had been created between the canine and the premolar. In short! Unbelievable and disappointing. Really a very unfortunate status .

6.- The future of Homo floresiensis

The future of Homo floresiensis is very promising. At the end of March the team of research restarted the excavations in Liang Bua. This season they are going to work in levels that are about 50,000 years old, with the conviction that new remains of this species will appear, which will settle any possible controversy about its true status.

Certainly, what we are going to say now is, for the moment, pure speculation, but it is too tempting an idea to pass up: are there more hobbits on the islands near Flores? Is that the only place where this strange experiment in human evolution took place? 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 to find possible sites of interest for future excavations*(39).

However, there are other closer questions that still remain: Why did Homo floresiensis become extinct? Were we the cause of their disappearance? Did our ancestors interact with them? What is the difference between their gene pool and ours? Today these are questions for which we still do not have solutions. What is certain is that, as Boyd and Silk state: "hominin evolution is more complex than we had imagined"* (40).

We said at the beginning that in human evolution, great discoveries always generate more questions than answers, and the "casofloresiensis" is no exception. The good news is that, on this occasion, we will not have to wait long to begin to have reasonable explanations for the questions raised here. However, we should be careful not to forget the words of the pre-Socratic philosopher Heraclitus of Ephesus when he said: "Nature loves to hide". The truth seems to do the same, so we have to admit that we may never succeed in unravelling all the enigmas surrounding our evolutionary history, including some of the most important questions concerning the admirable Homo floresiensis: that great little mystery of human evolution.

Notes

1. Ayala and Cela Conde recognise this fact, but attribute it to basic errors: "Each finding of a previously ignored fossil form usually resolves some of the previous doubts, but at the price of raising new ones that often produce the sensation that the panorama of our origins is something very confusing about which there is a lack of reliable knowledge (...)....) In reality, the problems caused by the new findings are, in many cases, the result of having previously sustained excessively speculative and false hypotheses" (Camilo José Cela Conde and Francisco Ayala: Senderos de la evolución humana; Alianza publishing house, Madrid, 2001, p. 86). Although it seems that they end up opting for caution: "There is still not enough evidence to be able to give an accurate portrait of the phylogeny of hominids in the Pliocene. More fossils are therefore needed to resolve the doubts. But those that continue to appear, if they clarify any dilemma at all, usually do so at the price of leading us to several more" (ibidem; p. 284). Lee R. Berger expresses himself with meridian clarity: "Each new finding raises as many questions about the nature of primitive hominids and their relationships as it provides answers" (Lee R. Berger: In the Footsteps of Eve; B.S.A., Barcelona, 2001, p. 42). An idea to which José María Bermúdez de Castro seems to agree when he states that: "Each finding comes to answer one or more questions, but always raises new questions" (J.M. Bermúdez: El chico de la Gran Dolina; Ed. Crítica, Madrid, 2002, p. 27). Nor does Jaume Bertranpetit Busquets seem to be alien to this line of thought, at least this is what is perceived when he maintains that: "The more we know, the more detailed we want to analyse the processes of change and, therefore, new gaps appear in the knowledge" (J. Bertranpetit: Viaje a los orígenes; Ed. Península, Barcelona, 2000, p. 109). This is why Luigi Luca Cavalli-Sforza says: "the scientist devotes a large part of his efforts to sowing doubts" (L.L. Cavalli-Sforza: Who are we?; Ed. Crítica, Barcelona, 1994, p. 85). And elsewhere he states in the following terms: "By way of final reflection, the impression one has when attending a scientific discussion like this is that there are many unanswered questions, and this is normal, because the more we know, the more questions we ask ourselves. I would divide them into two subgroups: a few recurring questions that remain unanswered, and a multitude of new questions that just a few years ago we did not even ask ourselves, the result of new findings and new interpretations" (VV.AA.: Antes de Lucy; Tusquets Editores, Barcelona, 2000, p.286).
2. This fatalistic sentiment is well captured by Berger, for whom we are always doomed to see: "somewhere, somehow, another fossil will appear that will force a revision of the prevailing theories" (op. cit.; p. 64).
3. M. Brunet, D. Pilbeam, Y. Coppens, L. De Bonis, Marcia Ponce De Leon, Christopher Zollikofer, et al.: A new hominid from the Upper Miocene of Chad, Central Africa; Nature, 418, pp. 145-151, 11. Cf. also, Patrick Vignaud et al.: Geology and paleontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature, 418, pp. 152-155, 11.VII.2002. And Cf. Henry Gee: Toumaï, face of the deep; Nature, Vol. 18, 11.VI.2002. As well as Bernard Wood: Paleoanthropology: Hominid revelation from Chad; Nature, Vol. 418, pp. 133-135, 11.VII.2002.
4. 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.
5. Cf. Tim D. White, Gen Suwa & Berhane Asfaw: Australopithecus ramidus, a new species of hominid from Aramis, Ethiopia; Nature, Vol. 371, pp. 306-312, 1994.
6. Y. Haile-Selassie: Late Miocene hominids from the Middle Awash, Ethiopia; Nature, Vol. 412, pp. 178-181, 2001.
7. 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. 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?; 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 hominid family tree by demonstrating that the variability and diversity of the hominid family tree is much greater than hitherto assumed. Cf. also Ron Clarke: New Fossil Genera; Science World, no. 228, pp. 24-28 and Claudine Cohen: Our Ancestors in the Trees; Science World, no. 228, pp. 28-33.
8. 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, C.S. Feibel, I. McDougall & C. Mark: New specimens andconfirmation of an early age for Australopithecus anamensis; Nature, Vol. 393, pp. 62-66, 1998. Cf. also M.G. Leakey & A.C. Walker: Ancient hominin fossils in Africa;research and Science, August 1997, pp. 70-75. For a more detailed knowledge on 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.
9. Cf. 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.
10. B. Asfaw , t. White, O. Lovejoy, G. Suwa et al.: Australopithecus garhi: A new species of early hominid from Ethiopia. Science 284, 629-635, 1999.
11. 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.
12. 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.
13. 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 1977, pp. 1392-1395.
14. M.J. Morwood, R.G. Roberts, et al.: Archeology and age of a new hominin from Flores in eastern Indonesia; Nature 431, 28 October 2005, pp. 1087-1091. 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.
15. Tim D. White, Berhane Asfaw, et al.: Pleistocene Homo sapiens from Middle Awash, Ethiopia; Nature 423, 12 June 2003, pp. 742-746. Cf. also, J. Desmond Clark, et. al.: Stratigraphic, chronological and behavioural contexts of Pleistocene Homo sapiens from Middle Awash, Ethiopia , Nature 423, 12 June 2003, pp. 747-752. 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.
16. The finding was released on press conference on 4 March 2005. The programs of study of these remains have yet to be published. Nature reported the news in a short grade signed by Rex Dalton: 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.
17. Sometimes one hears such pessimistic statements as those made by Boy and Silk when they state that: "The uncertainties of the hominid fossil record easily discourage us and make us doubt that we know certain facts about our ancestors"; (Robert Boyd and Joan B. Silk: How Humans Evolved; Ariel, Barcelona, 2001, p. 328).
18. Boyd and Silk are of this opinion when they state that: "the late Miocene fossil record tells us little about the creature that connects the great apes of the jungle with modern humans" (op. cit., p. 290). Ayala and Cela Conde are of the opinion that: "When talking about the evolution of hominoids during the Miocene (...) it is not easy to establish evolutionary connections going back to that time. It must be recognised that we do not have any certain evidence about the phylogenetic relationships existing between the Miocene hominoids and both the great apes and the present-day hominids" (F. Ayala and C. J. Cela Conde: op. cit., pp. 169-170). Roger Lewin states in the following terms: "Establishing phylogenetic relationships vertically or within any particular time period is therefore extremely risky, if not impossible, with the present patchy fossil record. Given the fossil gap that precedes the fossil hominoid record and the even greater hiatus that precedes the modern African great apes, any conjecture about the identity of the ancestor of modern hominoids can be no more than a conjecture" (R. Lewin: Evolución humana; Ed. Salvat, Barcelona, 1994, p. 167).
19. Most palaeoanthropologists think that we must be an australopithecine, without agreeing on agreement on which species. However, very authoritative voices (Richard Leakey, for example) disagree and claim that we come from some as yet unknown species of hominid.
20. For some it was habilis, for others rudolfensis; but there are those who believe (Bernard Wood) that habilis is actually Australopithecus, while some scientists (Meave Leakey and Allan Walker) maintain that rudolfensis is not a human but a member of the genus Kenyanthropus. So, as Lee R. Berger says, to the question: What was the first species of Homo (we have to answer that) at the moment there is no answer final" (op. cit., p. 51).
21. With great perspicacity Arsuaga observes that: "if there are classification problems with living species, let the reader judge what problems the palaeontologist encounters when working with fossils" (J.L. Arsuaga: La especie elegida; Ediciones Temas de Hoy, Madrid, 1999, p. 41).
22. Richard Leakey expresses himself with this forcefulness in this respect: "The important question of the origin of modern humans remains unresolved, despite the wealth of information that has been contributed to its interpretation" (R. Leakey: The Origin of Humanity; Ed. discussion, Barcelona, 2000, p. 137).
23. Jean Chalin: Un millón de generaciones; Ed. Península, Barcelona, 2002, p. 73.
24. In fact, its technical name is: LB 1, i.e. Liang Bua specimen 1.
25. 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.
26. Data calculated from a virtual reconstruction of the skull using computed tomography (CT) techniques.
27. 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.
28. D. Falk, et. al.: The brain of LB1, Homo floresiensis; op. cit.
29. 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.
30. Juan Luis Arsuaga, for example; even José Manuel Bermúdez de Castro.
31. In Larry Barham: op. cit., p. 6.
32. It is curious that Dubois went to Indonesia to look for the missing link as a convinced Darwinist, since the Down biologist postulated that it should be found in Africa, since that is where humans coexisted with the current large anthropomorphs that most resemble them (gorillas and chimpanzees).
33. In Larry Barham: op. cit.
34. "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: Flores Man; research and Science, April 2005, no. 342, p. 28).
35. Of course, what Tattersall says about the erectus of Ngandong in Java would be totally valid for the floresiensis. Given that: "the age of the erectus of Ngandong, in Java, is 40,000 years old, it means that it was necessary to admit an evolutionary history of their own for the hominids of that region, perhaps, for millions of years" (Ian Tattersall: Contemporary hominids;research and Science, March 2000, nº 282, p. 18).
36. Meike Köhler and Salvador Moyá: Reduction of brain and sense organs in the fossil insular bovid Myotragus. Brain Behav. Evol. 63, 125-140 (2004).
37. Rex Dalton: Fossil finders in tug of war over analysis of hobbit bones; Nature 434, 3 March 2005. Cf. also Elisabeth Culotta: Battle erupts over the "Hobbit" bones; Science 307, 25 February, p. 1179.
38. Cf. Elisabeth Culotta: Discoverers Charge Damage to 'Hobbit' specimens; Science 307, 25 March 2005, 1848.
39. Rex Dalton: Looking for theancestors; Nature 434, 24 March 2005, pp. 432-434.
40. R. Boyd and J.B. Silk: How Humans Evolved; op. cit., p. 328.

Introduction

The finding of a new human species that must have become extinct, at the latest, around 12,500 years ago (12.5 Kyr.) and, therefore, coeval with our own, with a little over a metre in height, a brain of a size analogous to that of the australopithecines of between three and four million years ago, and scarcely larger than that of today's chimpanzees, has been considered the most important finding of the last fifty years in the field of human palaeontology. Science magazine even ranked it as the most important scientific finding of 2004.

Palaeoanthropology is a branch of science that has the good fortune, or misfortune, to see each of its major discoveries generate more questions than answers1. It opens more doors than it closes. The case of Homo floresiensis is no exception. Sometimes this fact reaches limits bordering on paroxysm: human palaeontology is the branch of science in which it is more frequent to see how once or twice a year an important finding is presented by its discoverers as a revolutionary fact that forces to restructure all the elements that make up the building of this science. In no other branch of scientific knowledge is a paradigm shift, or at least a serious restructuring of the existing paradigm, proposed so frequently2 .

The most ill-intentioned minds may think that, in the uphill struggle for a share of the scarce funds for research in this field, the most spectacular and revolutionary projects have a better chance of getting a share of the cake. We are of the opinion that the real causes must lie elsewhere. Let's look at it.

Although the first human fossils were discovered in 1830, palaeoanthropology is a very young science. In fact, at that date, the Belgian anatomist Phillip Charles Schmerling found three skulls in the Belgian cave of Engis; the first was very deteriorated, the second belonged to an anatomically modern human (i.e. someone of our species), but the third is that of a Neanderthal child. In 1848, during fortification work on the Rock of Gibraltar, another fairly complete Neanderthal skull was discovered at Forbes Quarry. However, in neither case were these fossils recognised as human remains belonging to a species other than our own and now extinct. This event did not occur until 1864, when William King (Professor at Queen's College, Galway, Ireland) proposed to include the fossilised remains found in 1856 in the Feldhofer cave, 20 metres above the river Düssel, in the Neander valley (this is precisely the literal meaning of the word "neander-tal"), near the German city of Düsseldorf, in a new human species, which he called: Homo neanderthalensis. Then in 1868 the remains of direct ancestors of ours were discovered with a little more than 30 Kyr, the so-called "Cro Magnon Man". In 1891 the Dutch doctor Eugen Dubois discovered in Java human remains that were more than one million years old and that nowadays are assigned to Homo erectus, which, for the time being, is one of the main candidates for the direct ancestor of Homo floresiensis.

Although since then, fortunately, there have been many discoveries, some of them really important, the truth is that we still have a lot to know. Unfortunately, we cannot share the triumphalist views that proclaim that the essentials of human evolution have been discovered and that only small details remain to be worked out. According to this way of interpreting the current state of our knowledge on subject of human evolution, it would seem that the edifice of our knowledge in this field would be practically finished, all that remains to be done is to put a framework on that door, an embossed fence on that window, and a few more coats of paint here and there.

Frankly, we would like this to be the case, but, as we have already said, we see status differently. It is true that we know so much more today than we did only a few years ago. In just a decade, new discoveries have been made:

a.- Four new hominid genera with their respective species: Sahelanthropus tchadensis3, Orrorin tugenensis4,Ardipithecus5ramidus kadabba6 and A. ramidus ramidus and Kenyanthropus platyops7).

b.- Three new species of Australopithecus: A. anamensis8, A. bahrelghazali9 and A. garhi10 .

c.- Four new human species: Homo georgicus 11, H. cepranensis12, H. antecessor13 and H. floresiensis 14.

d.- And a subspecies of our species: Homo sapiens idaltu15 .

In addition to this, there have been numerous finds of hominin remains assignable to already known genera and species, but also a large number of remains not yet assigned to any genus and species; for example, early last March Yohannes Haile-Selassie announced that his team had found hominin remains 4 million years old (4 Ma.) old hominid remains that were already bipedal, but cannot yet be assigned to any genus or species16 ; the same is true of "Big Foot", fossil remains more than 3 Ma. old found by Ron Clarke in Sterkfontein, South Africa, last decade.

It is true that the fossil record, always very meagre , has become much fatter recently; and, fortunately, it looks set to become much fatter in the very near future. But it is also true that the questions core topic remain unanswered, without a satisfactory answer. Thus, we still do not know which was the Miocene hominoid that gave rise to the hominid family, i.e. we do not know who was the last common ancestor of hominids, panids and gorillids18 , nor which was the first hominid that opened the path that would lead to our lineage. Nor do we know which was the pre-human hominid that gave rise to our genus .19 It is not even entirely clear who the first humans were;20 indeed, there are palaeoanthropologists who are finding it increasingly difficult to define what man is. This is just one button sample of the problems we have in relation to phylogenies21; but the difficulties are no less in other matters: we thus have only a highly hypothetical sketch of the emergence of human consciousness in general and modern human consciousness in particular. We do not know who were the first humans to speak, nor when they began to do so; moreover, we will never know what their mental Structures were, that is, we will never know what was the symbolic universe that flowed through their minds. Not only do we not know how our genus emerged (sit venia verbo), but it is also unclear where our species came from .22 We could go on listing many other important questions that still await not only the solution to the enigma, but at least a satisfactory answer (When did bipedalism emerge and what was its cause? Who was the maker of the first tools? etc.).

The cause of all this? H. Vallois was able to explain it clearly when he stated that reconstructing human phylogeny from the fossil record we have is a bit like trying to reconstruct the plan of Paris from the protruding towers of a flood that would have inundated it all. We liked to use the example of the jigsaw puzzle, until three years ago, when we found it explained by Jean Chalin, to whom we therefore gladly cede the floor: "Imagine," says the French palaeontologist, "that we embark on an operation to put together a puzzle of more than a million pieces of which we only have between 150 and 200, and that we ignore the details of the final drawing for which we only have a few points from reference letter in the upper part of the puzzle, that is, from the present-day data (...)....) That is the goal of the palaeontologists"23. No comment is necessary.

Although human palaeontology has almost a century and a half of factual existence, as a science in the strict sense of the term it is much younger. Only in the last few decades has it been making explicit the methodological elements that have allowed it to grow as a fully-fledged empiriometric science. Perhaps in this relative youth lies one of the keys to understanding the incessant convulsions that its paradigm undergoes every year. It is very striking to see how, in this branch of science, almost every major finding forces us to rethink everything. In palaeoanthropology, the outline described by Thomas S. Khun in his work The Structure of Scientific Revolutions does not seem to apply. Here, there have never been long periods of calm in which the paradigm has lived peacefully in the quiet lap of the academic community, those periods which Khun calls "normal science". In this branch of scientific knowledge the paradigm has always been the subject of a lively and heated discussion.

Then we will see: where, when and how Homo floresiensis was discovered: the last great milestone that forces us to rethink the history of the human evolution, as we understood it until now. Then we will see its morphological characteristics (what it was like); its ecology (how it lived); what lithic industries it made (its technology); what its intellectual capacities might have been; the problem posed by its origin and evolution; the controversy surrounding the custody and study of its remains, as well as their interpretation. We will also have to pay close attention to result of the genetic programs of study which has already been commissioned. Finally, what other surprises may the future of palaeoanthropological research in this geographical area hold for us: will there be other human species other than ours and floresiensis waiting to be discovered? Alexander Koyré defined the Renaissance as the time when everything was possible: mutatis mutandis, it seems that, from the finding of Homo floresiensis, we can say the same about the human evolution. Or at least we have to recognise that this finding has to open our minds and make us aware that most probably there are still many surprises to be discovered in human palaeontology, some of which will undoubtedly be linked to Homo floresiensis.

1.-Location of the Island of Flores

Flores is a small tropical island in the Indonesian archipelago. To the west are the islands of Java and Bali, to the northwest Borneo, to the north the Celebes (Sulawesi), to the southeast Timor and to the south Australia.

It is approximately 360 km long and ranges in width from a maximum of 60 km (in the western part) to less than 20 km in parts of the eastern part. At 14,000 km2 Flores is almost three times the size of the Balearic Islands.

To the west of Flores is the island of Comodo, famous for the largest reptiles in the world: the Commodus Dragon, which was apparently part of the per diem expenses of Homo floresiensis.

2.- The finding and its publication

In October 2004 Flores became world famous when it was announced that the skeleton of a human being measuring just over one metre had been discovered there. It was the remains of a woman who had died as an adult, having died some 18,000 years ago (18 Kyr). The surprising thing is that her size and her physical features seemed to justify assigning her to a new, hitherto unknown human species: Homo floresiensis. To make matters worse, it turned out that her brain did not exceed the size of a chimpanzee; moreover, her remains had appeared in the same stratum in which thousands of lithic tools were found, with a level of development similar to what they had reached among other humans, such as the Neanderthals or the Sapiens.

Each of the above-mentioned elements alone presents a whole challenge for the scientific research . The universal media impact was therefore more than justified. From a scientific point of view, the news was truly unbelievable. If a paleoanthropologist had wanted to play a joke on a colleague on 28 December, it simply would not have stuck; no one would have believed such a thing.

But it was no joke. The advertisement of such a fabulous finding was published in the prestigious journal Nature. The articles concerning the finding had passed the sieve of a rigorous committee of experts and had the nihil obstat of the prestigious archaeologist Christopher Stringer. A magazine that puts its reputation on the line, week in, week out, cannot risk publishing speculative nonsense. The finding of the existence of a new human species that had been contemporary to us and had recently become extinct was serious.

The finding had been made in September 2003, when a team of research led by: Mike Morwood and Peter Brown (both from the University of New England, Armidale, Australia) found in sector VII of Liang Bua cave the skull and part of the postcranial skeleton of an individual belonging to a new human species.

3.- Location of the finding

Liang Bua is a karst cave located in the centre of the western part of the island, about 14 km northwest of Ruteng, the capital of Manggarai department ; and about 25 km from the northern coast, washed by the Flores Sea. It is 500 metres above sea level, and its training is due to the action of the Wae Racong River, which is now about 200 metres away from the cave and 30 metres below the level of the cave.

Sector VII is the place where the skeletal remains of Hobbit (the affectionate nickname with which her discoverers have decided to name this female Homo floresiensis, due to her short stature24 ) have been found. It is a small area of 4 m2 located very close to the eastern wall. The skeleton was found at a depth of almost six metres (5.9 m), in a very small area: approximately 500 cm2 (20x30 cm). Animal remains and stone tools were found at the same level. Dated by the carbon-14 method, the upper layers of this level date to between 11 and 13 Kyr.

At first, its discoverers thought they had stumbled upon the skeleton of a child. But when they analysed the teeth, they were able to see that the wear and tear was consistent with the longevity of an adult. Judging by the shape of the pelvis, it seems that the skeleton was that of a woman who may have died at the age of 30.

If it was not a boy, then could it be a pygmy subject of our species? The authors of the finding discard this hypothesis, arguing that the short stature of pygmies is due to the fact that their body growth stops just at the beginning of adolescence, but the brain has already finished its normal growth rate, so it is already the size it will be when the individual is an adult. That is to say: a pygmy sapiens is very tall leave but has a brain with the average volume of our species and, therefore, with a much higher rate of encephalisation than that of floresiensis.

Nor are we looking at a female with growth anomalies, as isolated remains have been found from other individuals that point in the same direction: small size as a specific characteristic and not as a sign of a growth anomaly.

Despite their diminutive size, they hunted animals such as extinct dwarf elephants (Stegodon), mainly their young; giant lizards, the famed Comodo dragon (still extant), snakes, turtles, frogs, rodents and bats. Since the bones of some of these animals have been found charred, it is believed that floresiensis must have mastered fire.

Thousands of lithic tools used for skinning, butchering, tanning or drilling have also been found at Liang Bua. Many of these tools appear in sediments that are 78 Kyr old. We know that sapiens did not arrive in Flores until about 12 Kyr ago. Who is the author of these tools from Flores, so similar to those made by the Neanderthals in Europe and the sapiens in Africa at that time? We still do not know for sure.

Shortly after her death, her body was covered by a thin layer of sediments. Radiocarbon and luminescence dating methods have been used to determine the age of these sediments in order to infer the exact dating of this hominid's remains. Two samples of the skeleton were dated by carbon-14 and both yielded a similar result : 18 Kyr.

In sector IV, a premolar was found with the same morphological characteristics as those found in the complete mandible of the hominid from sector VII (Hobbit), and has therefore been assigned to the same species; it is also attributed an age of 18 Kyr. Below this premolar, a molar belonging to a young individual of Stegodon has been found which, dated by thermoluminescence, gives an approximate age of 74 Kyr.

Even more ancient are the skeletal remains of a hominid that could be around 95 Kyr. In any case, no less than 74 Kyr. The remains include a radius of an adult individual who must also have been about a metre long. This stature is what has made them to be provisionally assigned to Homo floresiensis, while awaiting the realization of programs of study that can further specify or confirm their specific assignment.

What were Hobbit's intellectual capacities? After a lively controversy, to which we will refer later, his discoverers, in partnership with the palaeoanthropologist Dean Falk and the radiologist Charles Hildebolt, have carried out a study of the LB1 skull, which was published at the beginning of March25. When Hobbit was presented to society in October 2004, it was estimated to have a brain volume of 380 cc; identical to the average volume of present-day chimpanzees, and a far cry from the 1350 cc of today's humans. The new volume now attributed to the brain of floresiensis is 417 cc.26, a figure that includes it within the characteristic parameters of the gracile Australopithecus, subject Lucy, 3 million years ago. However, what most struck Falk was not so much the volume, but the structure of the brain: a cranial size typical of an australopithecus but with a clearly human brain structure. Y... how can we know this? The brain does not fossilise, but it 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: a.- it had highly developed temporal lobes (areas that in our genus are associated with language comprehension, in them we find Wernicke's area and Broca's area ), and the cerebral area that controls hearing and b.- the frontal lobe (area associated with the control of rational skills and planning for the future) is also highly developed. These data allow us to speculate on 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 discovered27 (a possibility also considered by Falk28, Morwood, Brown29 and others30). 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. "31 Giants of human palaeontology, such as Tim D. White and Chris Stringer also disagree with Jacob's interpretation. The controversy has even reached issues such as custody and access to the fossils. Until now 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 at his disposal again for their study. Of course, Homo floresiensis is going to give a lot to talk about in the near future, as its semi-fossilised remains have become, for several reasons, some real "bones of discord", as we will be able to see a little further on.

4.- How did Homo floresiensis arise?

One of the great enigmas surrounding this hominid is how its species arose. For the moment, its discoverers suppose that it must have originated from Homo erectus. It is not for nothing that this human species was discovered in Java at the end of the 19th century by the Dutch doctor Eugen Dubois.

In 1887 he set off for Indonesia to find fossil evidence that would prove Darwin right. In 1859, Darwin had published his famous work, The Origin of Species, in which he claimed that present-day living things came by evolution from earlier ones, and these from others, until they were traced back to a first living thing from which all living things that had ever existed descended. The mechanism by which this phenomenon took place, the engine of evolution, was the natural selection of mutations which, arising at random, favoured adaptation to the environment and, therefore, survival. Dubois was born a year before the publication of Darwin's work and grew up in the midst of all the controversy raised by his thesis , especially when applied to our species, after the publication in 1883 of The Origin of Man. In this work Darwin argued that we were no exception in nature; that is, that man also came about by biological evolution from other animal forms and by the same mechanisms (natural selection of random genetic mutations). All the qualities that defined man as such had emerged, progressively, from his purely biological evolution. The then famous German biologist Ernst Haeckel, a fervent supporter of Darwin's thesis , deduced that there must be an intermediate form between present-day man and the primates, which would undoubtedly be the missing link postulated by Darwin. Haeckel called this intermediate form Pithecanthropus alalus ("Speechless ape-man").

As mentioned above, Dubois travelled to Indonesia in 1887 to find this missing link32 . After several years of work fortune finally smiled on him in 1891. On a terrace of the Solo River, near the village of Trinil, he finally found a calotte (the cranial vault), a femur and a molar. The femur's unmistakable signs of bipedal gait led Dubois to assign it to a new species: Homo erectus. Controversy rages over the age of these fossils. Originally it was thought that they were about 1.2 million years old; they could even be as old as 1.4 million. But in the 1990s, geochronologists Carl Shiwsher and Garniss Curtis assigned much older ages to the fossils than previously assumed. They claim that the Trinil remains could be astonishingly old as 1.8 million years. But many scientists are sceptical of this latest date and claim that there may have been stratigraphic contamination of the sediments. More controversial are the dates of their extinction, which, according to Shiwsher, would be as old as 30,000 years. If they were true, they would turn the erectus of Java into contemporaries of the sapiens and floresiensis.

In principle, it is reasonable to assume that Homo floresiensis comes from Homo erectus. The assumption is based on a number of shared traits, but also on the fact that erectus is the only ancestral species we have documented in the fossil record from that area.

On the other hand, there are those who claim to see more resemblance with Homo habilis. In fact, Homo floresiensis shows traits of a mosaic evolution: together with derived characters it preserves other shared ones; among its anatomical traits there are some that, indeed, evoke H. habilis (for example the stature) or even Homo georgicus (a human species named after the remains found in Dmanisi, Georgia). Such is the view of Juan Luis Arsuaga, one of the three famed co-directors of the popular Atapuerca palaeoanthropological sites in Burgos. But it is also the view of Colin Groves of the Australian National University in Canberra33. Even Morwood and Brown, in their reply to Groves admit that they consider the possibility that floresiensis could derive from a human form previous to erectus; perhaps Homo habilis; even some human species, not yet found, and which had already reduced its size in a state of isolation in other small islands. Both options are tremendously revolutionary and in the absence of conclusive evidence it is best to opt for a conservative position: Homo erectus was present in Java 1.8 Ma. ago, so it had more than enough time to reach Flores, in one way or another, and evolve there into the human species we are discussing.

What would happen if Homo floresiensis descended from Homo habilis or Homo georgicus? Quite simply: a large part of the history of human evolution would have to be rewritten, changing many concepts of the classical paradigm, for example: that Homo habilis had never left Africa. This idea begins to be questioned from the moment it is recognised that the remains from Dmanisi are more similar to habilis, although not identical, than to Homo ergaster or erectus; so it has been decided to assign them to a new species: Homo georgicus. We must stop to discuss, even very briefly, the case of the Dmanisi fossils, since it is not totally ruled out that they may be related to the Flores fossils.

In 1991 the team of Leo Gabunia, Abesalom Vekua and David Lordkipanidze happened to find a series of human remains in the Georgian town of Dmanisi. It was estimated to be as old as 1.8 Ma., a truly spectacular discovery that was greeted with great scepticism at the time, as the first humans to leave Africa were assumed to have left much later. The site at Tel Ubeidiya (Israel) yields maximum dates close to 1.4 million years old, the same date that was then attributed to the Indonesian sites of Modjokerto, Trinil and Solo.

The Dmanisi remains were initially attributed to either Homo ergaster or Homo erectus. But in 1999, two new skulls were discovered that forced the question to be reconsidered. The small volume of the skulls, as well as other archaic features, suggested that these human remains did not belong to ergaster or erectus, but were more reminiscent of habilis, although they were not completely identical, as they showed some more modern features not detected in habilis. Therefore, the Georgian team of scientists opted to include it in a new human species: Homo georgicus.

It need not be impossible that habilis left Africa and along the way evolved into georgicus; in fact it is a matter of advancing the outline which proposed that ergaster was the first human to leave Africa, giving rise to the erectus clade during its migration through the Near East. That would be a lot, but to suppose that Habilis or georgicus reached Java and there evolved into floresiensis, or that they sailed to Flores to give rise to that species on that island, is something for which we are not yet mentally prepared, much less to accept that it was Australopithecus who made such a journey, as Kate Wong suggests, alluding to Milford Wolpoff34. Let us leave this hypothesis aside for the moment, although, from what we are seeing, in human evolution we cannot close our minds to anything that makes sense.

Let us focus on the hypothesis that, for the moment, seems most plausible. Attribute an arbitrary age of 20 years to each generation and assume that a generation moves an average of 20 km. This would give us a rate of movement of one kilometre per year for these human groups. This means that in less than 40,000 years, Ergaster people starting a migratory movement from Kenya or Ethiopia could have reached any part of Southeast Asia or the Chinese coast, after leaving Africa through the Palestine corridor and skirting the Red Sea and Persian Gulf along the coast of the Arabian Peninsula, and continuing along the Indian coastline to Southeast Asia and Java, which at certain periods has been joined with Indochina and Malaysia to form the Sunda Peninsula.

It is therefore perfectly plausible that Homo ergaster left Africa 1.8 Ma ago, and shortly afterwards, from the point of view of geological time, was already in present-day western Indonesia. If Carl Shiwsher's dating is correct, this hypothesis would be corroborated by empirical data. In any case, Homo erectus was already in present-day Java more than a million years ago.

Did Homo erectus colonise the island of Flores? If so, when did he do it? In 1999, Morwood and Brown's team unveiled to the world finding stone tools that could be 840,000 years old. The authors argue that they are of anthropogenic origin, which means that humans could have inhabited these lands by that date. Some experts advise caution before ruling out the possibility that their origin is due to purely natural causes, i.e. the action of meteorological agents rather than intentional human manipulation.

Let's suppose they really are stones carved by humans. Who made them? Until now it has been assumed that it would have been theerectus; but, in view of what we have seen, we cannot close the door to new surprises related to these dates. However, the authorship of the morphology of these stones is not the only admirable thing in this case. If humans were responsible for the carving of these artefacts, how were they able to reach Flores 840 Kyr ago if it seems that the island was never connected by an arm of land to the mainland?

When the Earth's climate cools, water tends to freeze and concentrate at the poles. Then the sea level leave and many continental shelf lands emerge. Some islands are joined to the continent by arms of land. Although the morphological configuration of the continents has not essentially changed in the last hundred thousand years, the land space potentially habitable by humans has; many regions now covered by water since the end of the last ice age have been emerged for millennia. The same was true almost a million years ago. At times, the sea level was as much as a hundred metres lower than it is today. There are numerous striking examples of this phenomenon: many of the islands that today form the Indonesian archipelago have been joined to the Asian mainland to form the Sunda Peninsula; Australia, New Guinea and Tasmania have been joined to form a single continent: Sahul; and Alaska and Siberia were linked by an arm of land called Beringia, right where the Bering Strait is today. But Flores seems never to have been linked to the Sunda Peninsula. Indeed, it remained beyond the visual horizon.

The great naturalist Alfred Russell Wallace, co-discoverer with Darwin of the theory of evolution by natural selection of randomly acquired characters, spent several years in the East Indies, then under Dutch political control, studying the boundary between two of the three great zones into which the faunas of terrestrial vertebrates are geographically divided. These two kingdoms are: the Arctogea (including Eurasia, Africa and North America) and the Notogea (including Australia, New Guinea and Tasmania). The third kingdom is the Neogene and includes South and Central America. In 1863 Wallace drew the natural boundary between the Arctogea and Notogea to the east of the islands of Mindanao (in the Philippines), Borneo and Bali. Thus, Sulawesi (or Celebes), the Moluccas, the smaller Sunda Islands and Timor were on the Notogean side. Thomas Henry Huxley, famous, among other things, as Darwin's great apologist, named this biogeographical divide after him: the "Wallace Line". Later scholars, however, pushed the line further and further east. There are no impenetrable geographical barriers, so the boundaries between the various biogeographic regions are always blurred and often overlap. To the west of Wallace's Line is the Sound shelf, and to the east the Sahul shelf. Crossing the Wallace Line is only possible in two ways: flying or sailing, either by chance or intentionally. The key questions are, then, who were the first humans to reach Flores? And when did they do so?

Let us continue assuming that the stones found by Morwood and Brown's team are lithic tools carved by men who lived on Flores 840,000 years ago (as they are not associated with bone remains we cannot attribute them to any specific species, although, for the moment, the best candidate is Homo erectus), this would obviously mean that the island was already populated at that time. The question, therefore, would now be, how did they manage to get there?

There are two hypotheses: navigation of fortune and intentional navigation. Although the exact origin of the primates of the New World is not known, some palaeontologists believe that they must have arisen from African congeners that crossed the Atlantic during the Oligocene period thanks to fortunate navigation. Although South America and Africa were then separated by 3,000 km, there are fossilised remains of rodents on both sides of the ocean that are so similar that researchers do not hesitate to link them, claiming that they managed to cross that great distance by chance, perhaps covering the route via islands.

But if it is already remarkable that Australia's first settlers sailed there 60,000 years ago at the latest, it is even more spectacular to suppose that the authors of those tools sailed to Flores 840,000 years ago!

If navigation was intentional, a minimum of shipbuilding and navigation techniques should have been mastered, however rudimentary they may have been. That the erectus, or any other human species of those times, had sufficient knowledge for the construction of some subject boat, however elementary it was, and of the minimum technique to navigate with an intention behind a deliberate goal , is something so exceptional that it is almost unbelievable; not even in the case that in that colonisation the technique of "frog-jumping" was used, that is: moving from islet to islet and from island to island, until arriving to Flores from Java. Between Bali, which was linked to the Sonda Peninsula, and Flores there are two relatively large islands: Lombok and Sumbawa, and other smaller ones, among them: Comodo. Although the distances from one to the other are not very great, many are beyond visual range. Therefore, even assuming erectus was able to navigate, how could he have known that by going out to sea he would find land? We can think of two reasons why he might suspect that not far from the farthest point his sight could reach there might be land:

1. The migratory flight of birds. Although we now know that they are capable of flying for hundreds of kilometres without resting, the first humans who supposedly sailed across Wallace's Line may have taken a very risky decision with a fortunate ending without being fully aware of the dangers involved.

2. Another option that might have awakened them to the belief that there was land signature beyond the horizon may have come from observing the plumes of smoke rising from some spectacular fire. A few years ago, a devastating fire in Indonesia was infamous for raising huge plumes of smoke, visible for hundreds of kilometres.

Whether fortunately or more or less deliberately, it is remarkable that just over 800,000 years ago there were already humans on the island of Flores. test Since no human fossils have been found from that time, the indirect evidence that the island was already inhabited by members of our genus is provided by the lithic industry mentioned above reference letter . Let us suppose that, indeed, they are stones carved by humans: what happened then with the population that was confined in the island? What was their evolution along the hundreds of thousands of years that elapsed from this supposed date of arrival until the extinction of the Homo floresiensis 12,000 years ago?35 Did the human species that arrived in Flores and, supposedly, gave rise, with time, to the Homo floresiensis, occupy other islands where they also evolved towards this same human morphology? Perhaps they evolved towards other forms?

Why is the physical build of Homo floresiensis so small? Flores is a relatively 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 make a better management use of food resources by making better use of them, thus making their viability possible.

Spectacular cases of body volume reduction have been reported in situations of geographical isolation on small islands. In Sicily, for example, adult elephants averaged as little as 250 kg. Fossilised remains of hippopotamuses weighing 400 kg have been found in Cyprus and Malta. On other Mediterranean islands, fossils of deer the size of dogs have been found.

However, explaining Hobbit's reduction in brain volume is much more complex and less well documented in the fossil record. Palaeontologist Salvador Moyá, from the Institut Miquel Crusafont de Sabadell in Barcelona, found fossilised remains of Myotragos, a species of ox that had reduced the size of its brain by half, in the Balearic Islands36. Explaining the reduction of brain volume in humans is extremely complex, since it is a predator (although it is possible that lions and hyenas, which are also predators, have reduced their brain volume by a third over the last 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? According to its discoverers, the two most plausible hypotheses are: On the one hand, that Floresiensis are the descendants of a population of Erectus that was confined to the island and drastically reduced its size in order to survive. But, on the other hand, the idea is gaining strength that floresiensis is the descendant of a population of pre-erectus (habilis, georgicus, or -perhaps- another species still to be discovered?) that arrived to Flores much longer ago than imagined until now and, therefore, they arrived already with a small body and brain size, without a process of reduction too significant. We have to remember that Homo habilis measured little more than one metre and its brain is around 600 cm3. Regarding these parameters, those of floresiensis are not particularly distant. Of course, if we compare him with the 1000 cm3 of endocranial capacity of erectus, the reduction of his brain is spectacular. Which of the two hypotheses is the correct one? Time will tell. Is there a third alternative? We shall see.

5.- The bones of discord

Following the publication of the spectacular finding a nasty controversy broke out. Teuko Jacob, Indonesia's leading authority on subject on human evolution, was not on the sidelines of research, but through a colleague who was part of the team working at Liang Bua, he was able to gain access to the Hobbit skeleton. Initially it was to be for a limited time, but nervousness and suspicions began to grow when he missed the successive submission deadlines to which he had committed himself. The protests of the Morwood and Brown team grew because even they could not access the research of the remains they had discovered. The back-and-forth was really serious37 . Jacob was even accused of having kidnapped Hobbit's remains. Moreover, the latter did not cease to maintain that the female floresiensis found was nothing more than a member of our species suffering from a growth anomaly, explaining the diminutive size of the brain by a microcephaly, something that Morwood and Brown rightly rejected out of hand.

Finally, in early March 2005, Jacob returned the Hobbit remains to his discoverers. But their surprise was great when they realised that their worst suspicions had been realised: Teuko's team's handling of the semi-fossilised remains of the female Florfloresiensis had been badly damaged38: the pelvis has split; the mandible is missing an incisor; the lower part of the mandible has fragmented in several places (the reconstruction has necessarily changed the physiognomy of this maxillary area); the upper rear part of the mandible is missing a fragment of bone; an empty space, previously non-existent, has been created between the canine and the premolar. In short! Unbelievable and disappointing. Really a very unfortunate status .

6.- The future of Homo floresiensis

The future of Homo floresiensis is very promising. At the end of March the team of research restarted the excavations in Liang Bua. This season they are going to work in levels that are about 50,000 years old, with the conviction that new remains of this species will appear, which will settle any possible controversy about its true status.

Certainly, what we are going to say now is, for the moment, pure speculation, but it is too tempting an idea to pass up: are there more hobbits on the islands near Flores? Is that the only place where this strange experiment in human evolution took place? 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 travelled to the neighbouring island of Lombok, west of Wallace's line, at the end of March to find possible sites of interest for future excavations39.

However, there are other closer questions that still remain: Why did Homo floresiensis become extinct? Were we the cause of their disappearance? Did our ancestors interact with them? What is the difference between their gene pool and ours? Today these are questions for which we still do not have solutions. What is certain is that, as Boyd and Silk state: "hominid evolution is more complex than we had imagined"40.

We said at the beginning that in human evolution, great discoveries always generate more questions than answers, and the "casofloresiensis" is no exception. The good news is that, on this occasion, we will not have to wait long to begin to have reasonable explanations for the questions raised here. However, we should be careful not to forget the words of the pre-Socratic philosopher Heraclitus of Ephesus when he said: "Nature loves to hide". The truth seems to do the same, so we have to admit that we may never succeed in unravelling all the enigmas surrounding our evolutionary history, including some of the most important questions concerning the admirable Homo floresiensis: that great little mystery of human evolution.

Notes

1. Ayala and Cela Conde recognise this fact, but attribute it to basic errors: "Each finding of a previously ignored fossil form usually resolves some of the previous doubts, but at the price of raising new ones that often produce the sensation that the panorama of our origins is something very confusing about which there is a lack of reliable knowledge (...)....) In reality, the problems caused by the new findings are, in many cases, the result of having previously sustained excessively speculative and false hypotheses" (Camilo José Cela Conde and Francisco Ayala: Senderos de la evolución humana; Alianza publishing house, Madrid, 2001, p. 86). Although it seems that they end up opting for caution: "There is still not enough evidence to be able to give an accurate portrait of the phylogeny of hominids in the Pliocene. More fossils are therefore needed to resolve the doubts. But those that continue to appear, if they clarify any dilemma at all, usually do so at the price of leading us to several more" (ibidem; p. 284). Lee R. Berger expresses himself with meridian clarity: "Each new finding raises as many questions about the nature of primitive hominids and their relationships as it provides answers" (Lee R. Berger: In the Footsteps of Eve; B.S.A., Barcelona, 2001, p. 42). An idea to which José María Bermúdez de Castro seems to agree when he states that: "Each finding comes to answer one or more questions, but always raises new questions" (J.M. Bermúdez: El chico de la Gran Dolina; Ed. Crítica, Madrid, 2002, p. 27). Nor does Jaume Bertranpetit Busquets seem to be alien to this line of thought, at least this is what is perceived when he maintains that: "The more we know, the more detailed we want to analyse the processes of change and, therefore, new gaps appear in the knowledge" (J. Bertranpetit: Viaje a los orígenes; Ed. Península, Barcelona, 2000, p. 109). This is why Luigi Luca Cavalli-Sforza says: "the scientist devotes a large part of his efforts to sowing doubts" (L.L. Cavalli-Sforza: Who are we?; Ed. Crítica, Barcelona, 1994, p. 85). And elsewhere he states in the following terms: "By way of final reflection, the impression one has when attending a scientific discussion like this is that there are many unanswered questions, and this is normal, because the more we know, the more questions we ask ourselves. I would divide them into two subgroups: a few recurring questions that remain unanswered, and a multitude of new questions that just a few years ago we did not even ask ourselves, the result of new findings and new interpretations" (VV.AA.: Antes de Lucy; Tusquets Editores, Barcelona, 2000, p.286).
2. This fatalistic sentiment is well captured by Berger, for whom we are always doomed to see: "somewhere, somehow, another fossil will appear that will force a revision of the prevailing theories" (op. cit.; p. 64).
3. M. Brunet, D. Pilbeam, Y. Coppens, L. De Bonis, Marcia Ponce De Leon, Christopher Zollikofer, et al.: A new hominid from the Upper Miocene of Chad, Central Africa; Nature, 418, pp. 145-151, 11. Cf. also, Patrick Vignaud et al.: Geology and paleontology of the Upper Miocene Toros-Menalla hominid locality, Chad. Nature, 418, pp. 152-155, 11.VII.2002. And Cf. Henry Gee: Toumaï, face of the deep; Nature, Vol. 18, 11.VI.2002. As well as Bernard Wood: Paleoanthropology: Hominid revelation from Chad; Nature, Vol. 418, pp. 133-135, 11.VII.2002.
4. 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.
5. Cf. Tim D. White, Gen Suwa & Berhane Asfaw: Australopithecus ramidus, a new species of hominid from Aramis, Ethiopia; Nature, Vol. 371, pp. 306-312, 1994.
6. Y. Haile-Selassie: Late Miocene hominids from the Middle Awash, Ethiopia; Nature, Vol. 412, pp. 178-181, 2001.
7. 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. 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?; 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 hominid family tree by demonstrating that the variability and diversity of the hominid family tree is much greater than hitherto assumed. Cf. also Ron Clarke: New Fossil Genera; Science World, no. 228, pp. 24-28 and Claudine Cohen: Our Ancestors in the Trees; Science World, no. 228, pp. 28-33.
8. 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, C.S. Feibel, I. McDougall & C. Mark: New specimens andconfirmation of an early age for Australopithecus anamensis; Nature, Vol. 393, pp. 62-66, 1998. Cf. also M.G. Leakey & A.C. Walker: Ancient hominin fossils in Africa;research and Science, August 1997, pp. 70-75. For a more detailed knowledge on 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.
9. Cf. 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.
10. B. Asfaw , t. White, O. Lovejoy, G. Suwa et al.: Australopithecus garhi: A new species of early hominid from Ethiopia. Science 284, 629-635, 1999.
11. 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.
12. 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.
13. 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 1977, pp. 1392-1395.
14. M.J. Morwood, R.G. Roberts, et al.: Archeology and age of a new hominin from Flores in eastern Indonesia; Nature 431, 28 October 2005, pp. 1087-1091. 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.
15. Tim D. White, Berhane Asfaw, et al.: Pleistocene Homo sapiens from Middle Awash, Ethiopia; Nature 423, 12 June 2003, pp. 742-746. Cf. also, J. Desmond Clark, et. al.: Stratigraphic, chronological and behavioural contexts of Pleistocene Homo sapiens from Middle Awash, Ethiopia , Nature 423, 12 June 2003, pp. 747-752. 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.
16. The finding was released on press conference on 4 March 2005. The programs of study of these remains have yet to be published. Nature reported the news in a short grade signed by Rex Dalton: 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.
17. Sometimes one hears such pessimistic statements as those made by Boy and Silk when they state that: "The uncertainties of the hominid fossil record easily discourage us and make us doubt that we know certain facts about our ancestors"; (Robert Boyd and Joan B. Silk: How Humans Evolved; Ariel, Barcelona, 2001, p. 328).
18. Boyd and Silk are of this opinion when they state that: "the late Miocene fossil record tells us little about the creature that connects the great apes of the jungle with modern humans" (op. cit., p. 290). Ayala and Cela Conde are of the opinion that: "When talking about the evolution of hominoids during the Miocene (...) it is not easy to establish evolutionary connections going back to that time. It must be recognised that we do not have any certain evidence about the phylogenetic relationships existing between the Miocene hominoids and both the great apes and the present-day hominids" (F. Ayala and C. J. Cela Conde: op. cit., pp. 169-170). Roger Lewin states in the following terms: "Establishing phylogenetic relationships vertically or within any particular time period is therefore extremely risky, if not impossible, with the present patchy fossil record. Given the fossil gap that precedes the fossil hominoid record and the even greater hiatus that precedes the modern African great apes, any conjecture about the identity of the ancestor of modern hominoids can be no more than a conjecture" (R. Lewin: Evolución humana; Ed. Salvat, Barcelona, 1994, p. 167).
19. Most palaeoanthropologists think that we must be an australopithecine, without agreeing on agreement on which species. However, very authoritative voices (Richard Leakey, for example) disagree and claim that we come from some as yet unknown species of hominid.
20. For some it was habilis, for others rudolfensis; but there are those who believe (Bernard Wood) that habilis is actually Australopithecus, while some scientists (Meave Leakey and Allan Walker) maintain that rudolfensis is not a human but a member of the genus Kenyanthropus. So, as Lee R. Berger says, to the question: What was the first species of Homo (we have to answer that) at the moment there is no answer final" (op. cit., p. 51).
21. With great perspicacity Arsuaga observes that: "if there are classification problems with living species, let the reader judge what problems the palaeontologist encounters when working with fossils" (J.L. Arsuaga: La especie elegida; Ediciones Temas de Hoy, Madrid, 1999, p. 41).
22. Richard Leakey expresses himself with this forcefulness in this respect: "The important question of the origin of modern humans remains unresolved, despite the wealth of information that has been contributed to its interpretation" (R. Leakey: The Origin of Humanity; Ed. discussion, Barcelona, 2000, p. 137).
23. Jean Chalin: Un millón de generaciones; Ed. Península, Barcelona, 2002, p. 73.
24. In fact, its technical name is: LB 1, i.e. Liang Bua specimen 1.
25. 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.
26. Data calculated from a virtual reconstruction of the skull using computed tomography (CT) techniques.
27. 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.
28. D. Falk, et. al.: The brain of LB1, Homo floresiensis; op. cit.
29. 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.
30. Juan Luis Arsuaga, for example; even José Manuel Bermúdez de Castro.
31. In Larry Barham: op. cit., p. 6.
32. It is curious that Dubois went to Indonesia to look for the missing link as a convinced Darwinist, since the Down biologist postulated that it should be found in Africa, since that is where humans coexisted with the current large anthropomorphs that most resemble them (gorillas and chimpanzees).
33. In Larry Barham: op. cit.
34. "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: Flores Man; research and Science, April 2005, no. 342, p. 28).
35. Of course, what Tattersall says about the erectus of Ngandong in Java would be totally valid for the floresiensis. Given that: "the age of the erectus of Ngandong, in Java, is 40,000 years old, it means that it was necessary to admit an evolutionary history of their own for the hominids of that region, perhaps, for millions of years" (Ian Tattersall: Contemporary hominids;research and Science, March 2000, nº 282, p. 18).
36. Meike Köhler and Salvador Moyá: Reduction of brain and sense organs in the fossil insular bovid Myotragus. Brain Behav. Evol. 63, 125-140 (2004).
37. Rex Dalton: Fossil finders in tug of war over analysis of hobbit bones; Nature 434, 3 March 2005. Cf. also Elisabeth Culotta: Battle erupts over the "Hobbit" bones; Science 307, 25 February, p. 1179.
38. Cf. Elisabeth Culotta: Discoverers Charge Damage to 'Hobbit' specimens; Science 307, 25 March 2005, 1848.
39. Rex Dalton: Looking for theancestors; Nature 434, 24 March 2005, pp. 432-434.
40. R. Boyd and J.B. Silk: How Humans Evolved; op. cit., p. 328.