La evolución, hoy. Evolucionismo: el hecho y sus implicaciones

Evolution today. Evolutionism: the fact and its implications.

Author: Mariano Artigas
Published in: Aceprensa, 44/95
date of on-line publication: 29 March 1995

Francisco J. Ayala, one of Spain's most internationally renowned scientists, has published a book in which he sets out, in a way accessible to the general public, the current state of the theory of evolution* (1). Ayala affirms that evolution is a proven fact, accepts the neo-Darwinian explanation of evolution, and points out that evolution is compatible with Christianity.

Francisco J. Ayala was born in Madrid in 1934, and has lived in the United States since 1961. He enjoys great prestige due to his work on biological evolution. He is a professor at the University of California and is currently President of the American Association for the Advancement of Science. Although he has already published several books on evolution, this book is aimed at a non-specialist audience. It attempts to explain in a clear way the central problems of biological evolution, and also touches on its cultural and religious significance.

Evolution as a scientific conclusion

The layman on subject often asks: to what extent has evolution been proven, can it be considered a scientific achievement or is it only a hypothesis that is still under discussion?

Ayala's answer is categorical: "The evolutionary origin of organisms is today an established scientific conclusion with a Degree of certainty comparable to other certain scientific concepts, such as the roundness of the earth, the rotation of the planets around the sun or the molecular composition of the subject. This Degree of certainty, which is beyond reasonable doubt, is what biologists point to when they claim that evolution is a "fact". The evolutionary origin of organisms is a fact accepted by biologists and by all well-informed people on the subject" (pp. 17-18); "the fact of evolution is already established final" (p. 19).

Ayala devotes a chapter of his book (chapter III) to setting out the main evidence for evolution, and stresses the importance of the evidence provided by recent advances in molecular biology. Of course, anyone who denies evolution today will have to confront all biologists and explain their unanimity. The anti-religious ideological conspiracy resource has little chance of succeeding, because both scientists and theologians often claim that evolution and religion are compatible. Theologians, as well as philosophers and almost everyone else, admit that evolution is a fact. About the only deniers are some fundamentalist Protestant groups in the United States, who continue to claim that the world is about 5,000 years old; meanwhile, scientists describe what the universe was like billions of years ago, study how the earth originated 4.5 billion years ago, and how life evolved from primitive organisms that existed on earth some 3.5 billion years ago.

At the end of chapter III, Ayala concludes that "there is probably no other scientific theory or concept that is as thoroughly corroborated as the evolution of living beings" (p. 62). In my view, he goes too far here, and sample that discussions of evolution are still often accompanied by an additional emotional charge. The evolution of life on earth is a unique historical process, whereas much other scientific knowledge concerns phenomena that can be repeated and even manipulated at will in laboratories.

The causes of evolution

How can evolution be explained? Ayala says that although much is known, much remains to be discovered. He is right. However, he perhaps fails to give an idea of all that remains to be discovered. The reason is that Ayala takes a clearly neo-Darwinian line and, in my opinion, tends to give too much credence to neo-Darwinian explanations.

In 1859, Darwin proposed his explanation of evolution by natural selection: heritable changes occur that provide advantages in the struggle for life, so that, in the long run, the organisms possessing these changes prevail. But Darwin knew nothing about these changes. Genetics, founded by Mendel and developed from 1900 onwards, made it possible to understand them: genetic mutations. In the 1930s, the synthetic theory of evolution (often called neo-Darwinism) was formulated, which explains evolution through a combination of mutations and natural selection. Many evolutionists accept that neo-Darwinism explains the essentials of evolution, and that there is no need to look any further.

Ayala writes: "By 1950 the acceptance of Darwin's theory of evolution by natural selection was already universal among biologists, the synthetic theory was accepted as correct, and controversies were limited to questions of detail" (p. 41). But Ayala's assessment is somewhat exaggerated, which is understandable because he is one of the leading authors of neo-Darwinism. According to other authors, as evolutionist as Ayala, Darwinian natural selection must be supplemented by important factors whose character we do not even know well at present.

There remain remarkable mysteries in evolution, especially concerning the origin of new organs and organisms. Neo-Darwinists often speak as if these mysteries are already essentially explained by natural selection. Ayala writes: "It is precisely as a consequence of natural selection that living things are organisms, i.e. they are well organised, consist of highly integrated parts that can carry out the functions appropriate to the organism's way of life" (p. 106). Natural selection is an "organising and creative process" (p. 141): like the artificial selection practised by farmers and breeders to improve plants and animals, natural selection would explain the production of new organs and organisms, without any plan, because the genetic changes that occur spontaneously in living things provide, in some cases, hereditary advantages that accumulate along the lines of better adaptation to the conditions of life.

The example Ayala provides to illustrate the effectiveness of natural selection refers to a rather simple case: the reproduction of bacteria and their resistance to streptomycin. The conclusion is clear: "as we illustrated with the bacterial example, natural selection acts step by step and thus produces combinations of genes that would otherwise be highly improbable" (p. 143). However, the real problem is much bigger: how did bacteria, and in general, all major types of organisation, come about, and is it correct to place all the responsibility on the combination of random genetic mutations plus natural selection?

Evolution and naturalism

At bottom, the problem has philosophical and theological dimensions. Modern physics was consolidated, in the 17th century, leaving aside metaphysical explanations: subject and its movement is what counts, as well as its mathematical and experimental study, and this has nothing to do with the old speculations. However, there still seemed to be a place for purpose in the world of the living, full of apparent plans and designs. Darwinism entered the fray, proposing an evolutionary explanation, in terms of random mutation and unplanned selection; thus evolution would complete the anti-metaphysical revolution.

Ayala poses the problem in exactly that way. He claims that Darwin is not only a great scientist, but "an intellectual revolutionary who inaugurates a new era in the cultural history of mankind. Darwin completes the Copernican revolution. ..... The workings of the universe cease to be attributed to the ineffable will of the Creator and pass into the domain of science, which is an intellectual activity that seeks to explain the phenomena of the universe by means of natural causes" (pp. 30-31). With his theory of natural selection, Ayala continues, "Darwin extends to the organic world the concept of nature derived from astronomy, physics and geology; the notion that natural phenomena can be explained as a consequence of immanent laws, without the need to postulate supernatural agents" (pp. 31-32); "he reduces to the domain of science the only natural phenomena that still remained outside it: the existence and organisation of living beings" (p. 33). The importance Ayala attributes to this fact is imposing: "Darwin completes the Copernican revolution, and with it Western man achieves his intellectual maturity: all the phenomena of the world of external experience are now within the reach of scientific explanations, which depend exclusively on natural causes" (p. 32).

Ayala's assertions are half-truths. They have their part of reason, no doubt: Copernicanism and Darwinism meant a broadening of the scope of science, which extended to many physical and biological phenomena. But they give a misleading impression when they seem to suggest that metaphysics has nothing to say about these phenomena.

Metaphysics has nothing to say, in fact, on the level of science itself. It cannot and should not enter skill with physics or biology in its own field. But it has something to say. Not much, of course; but what little it has to say is very important. In our case, the question core topic is: can it be admitted that everything that exists, including organisms and the whole system of nature, including the human person, is the simple result of blind natural forces, should it not be admitted, rather, that in nature we find metaphysical dimensions that science cannot explain, and that refer to explanations that lie beyond nature, in the metaphysical realm that philosophy and theology deal with?

In fact, Ayala has nothing against metaphysical dimensions. He even claims that science cannot deal with them, when he explains that evolutionism and Christianity are compatible.

Evolutionism and Christianity

On the one hand, Ayala explains that creation from nothing "is a notion which, by its very nature, remains and will always remain outside the realm of science", and adds that "other notions which are outside the realm of science are the existence of God and spirits, and any activity or process defined as strictly immaterial" (p. 147). Indeed, for something to be studied by the sciences, it must include dimensions Materials, which can be subjected to controllable experiments: and this is not the case with spirit, nor with God, nor with creation.

On the other hand, Ayala takes up the view of theologians that "divine existence and creation are compatible with evolution and other natural processes. The solution lies in accepting the idea that God operates through intermediate causes: that a person is a divine creature is not incompatible with the notion that he was conceived in the mother's womb and that he is maintained and grows by means of food.... Evolution can also be regarded as a natural process through which God brings living species into existence from agreement with his plan" (pp. 21-22).

Ayala adds that most Christian writers admit the theory of biological evolution. He mentions that Pope Pius XII, in a famous 1950 document, acknowledged that evolution is compatible with the Christian faith. And Pope John Paul II, in a 1981 speech , repeats the same idea.

When it is said that some Christian fundamentalists oppose evolution, it is important to bear in mind that these are almost always very active Protestant minorities in the United States. Ayala alludes to this problem, which he knows well, because these groups have brought major legal actions in the courts to implement their ideas about the teaching of evolution in schools, and Ayala is one of the most important scientists who have had to intervene in these proceedings to clarify what belongs to science and what belongs to religion. He states: "American anti-evolutionists continue to seek ways to prevent the teaching of evolutionary theory, which they still regard as anti-religious, rather than simply 'non-religious', as is any other scientific theory" (p. 24).

Ayala's ideas on the compatibility between evolution and Christianity are objective and clearly expressed. And they show that, alongside the phenomena studied by the sciences, there are metaphysical problems that cannot be solved using scientific data alone.

Unresolved issues

However, greater clarity could be achieved in some respects. Particularly on two: those concerning purpose and the human spirit.

With respect to finality, Ayala seems too intent, like many neo-Darwinists, on claiming that evolution explains the appearances of directionality in the living world: to understand this apparent finality, natural selection would suffice, which is a set of natural processes that is not directed towards any goal, that does not respond to any plan. However, Ayala also affirms, and rightly so, that evolution is compatible with the existence of a divine plan. This is indeed the case.

I would have liked Ayala to have explained these aspects better. One might think that perhaps that would have taken him too far from his purpose. However, Ayala has been writing about this topic, also in specialist journals, for many years. He says interesting things, acknowledges that there are some kinds of finality in nature, and even seems to think that there is a divine plan (because, if I am not mistaken, Ayala is a believer). But some aspects are not very clear. Admittedly, the problem is not a simple one: it is a question of recognising, at the same time, that in evolution there are many processes which, when viewed "from the tiles below" (for us), are coincidental, although when viewed "from the tiles above" (for God, who is the First Cause of everything) there is no such thing as chance. And to explain it clearly.

With regard to the human spirit, Ayala devotes a large part of the prologue to his book to it, and some other sporadic allusions. He implies that, in part, it can be studied by science, insofar as it has biological roots, and alludes, although he does not go into topic, to the Christian doctrine according to which the spiritual human soul is specially created by God. The problem, again, is not an easy one. Man is not pure spirit, but a unitary being that is both corporeal and spiritual. What Ayala says in this respect can be well understood, although it could also be expressed better and more clearly.

There are still more points that could be better explained. Indeed, although philosophical and theological studies in recent decades often include important references to evolution, we are still far from having achieved deep and clear explanations that integrate scientific knowledge with the metaphysical perspective.

In any case, Ayala's book deserves a welcome. It represents a fairly successful effort to make the main ideas related to evolution accessible to the general public, and it is by a world-class scientist. It explains clearly enough that evolutionism and Christianity are compatible, and why. I have pointed out some aspects which, in my opinion, could be improved; but I have also noted that these are not trivial problems, which are not even always clearly addressed by professional philosophers and theologians.

  1. Francisco J. Ayala. The theory of evolution. From Darwin to the latest advances in genetics. Ediciones Temas de Hoy,