Truth and False in Darwinism

Darwinism

 

The Darwinian theory, usually rendered in shorthand as the theory of “descent with modification by means of natural selection,” may be reduced to a syllogistic core that goes something like this:

 

(1)   Variation. All creatures that reproduce (sexually or asexually—it doesn’t matter) will produce offspring that vary slightly from themselves. An offspring might have slightly longer legs, or a slightly shorter beak, or slightly more hair, than its parents, and so it is said to vary. It is important to say that Darwin often claimed that he did not know how or why variations occur, only that they do occur. No parents’ child is identical to its parents, but how it will vary no one can predict. Darwin could often do no better than to say that any variation from parent to child is due to what we must, in our ignorance, call chance.

 

(2)   Heritability. Variations are often passed along in reproduction. Children with longer legs or more hair are likely to have children with these same traits, or even with these same traits more pronounced, and so on down the line of generation. In other words, variations often have a tendency to be preserved.

 

(3)   Competition  for survival. More creatures are born in  every species or group than can normally survive. They reproduce faster than the resources upon which they depend for sustenance. Therefore, some— actually many—must perish, as a regular fact of life. Only the few ever survive. This phenomenon came to be called by Darwin “survival of the fittest,” an expression that was invented by Herbert Spencer and brought to Darwin’s notice by the co-discoverer of the theory of natural selection, A. R. Wallace.

 

If these three events occur in nature—and Darwin was certain they did—then the mechanism of Natural Selection would allow evolution to happen.

 

(4)   Natural Selection. This principle determines who are the winners and losers in the perpetual struggle for existence. Those creatures that have varied in “favorable” directions are more likely to survive than those that have not varied, or have varied in unfavorable ways. For example, in a climate where longer hair provides a better protection against death by freezing than shorter hair, a variant individual with longer hair will be “selected” by nature to survive against its rivals who have been born with shorter hair, and this successful variant is likely to pass along the winning trait to its offspring. Again, Darwin did not claim to know how or why some individuals happened to vary—happened to be born with longer hair in our example—but only that if they did vary in favorable directions, they had a better chance to be selected for survival than ones that did not vary.

 

Of these four parts or ideas of the theory, this book is mainly about the first—variation—and even more narrowly, only variations that Darwin attributed to chance. The other ideas, of course, are fundamental to the theory, and no one believes that Darwin ever wavered from his belief in them, or in the primacy of natural selection among other factors that play a role in evolution. What is usually at issue in arguments for a changing Darwinism, rather, is the role played by “chance” in explaining variation. This idea more than any other sets Darwin’s theory apart from all other evolutionary theories in his day, and thus is important for establishing Darwin’s theory as distinctively “Darwinian.” The idea of “chance,” and the role it plays in the modification and “transmutation” of species, remained steadfast and the same in Darwin’s thought from his first revelations in 1837–1838 about what goes on in nature to all subsequent works where he addressed the question.  It is also, as I shall show, the one part of his theory that underwent the most dramatic changes in exposition.

 

These changes, directly and indirectly, account in turn for most of the suspicion that Darwin actually changed his mind, even though those who bring forward this argument have not been entirely clear about the importance of this shift for their own arguments. For example, one typical argument is that Darwin became more “Lamarckian” over the years. This is generally taken to mean that he came to strengthen a role for so-called “use-inheritance” in evolutionary change. What generally goes unnoticed in these accounts is that “use-inheritance” can only be strengthened by diminishing a role for something else, and that something else is usually “chance.” In fact the impression that Darwin strengthened “use-inheritance” is generated in part by the fact that he did (in words) reduce or even disguise the role that he had earlier assigned to chance. But if he did not really change his mind about chance, he did not really change his mind about use-inheritance.

 

 

Criticism of Darwinism

 

Indeed, there are few in America today who will defend naturalism perse; though they may hold it privately, they are reluctant to admit to it publicly.

 

We may ask, What do we mean by naturalism? There are at least three senses. First, naturalism is committed to a methodological principle within the context of scientific inquiry; i.e., all hypotheses and events are to be explained and tested by reference to natural causes and events. To introduce a supernatural or transcendental cause within science is to depart from naturalistic explanations. On this ground, to invoke an intelligent designer or creator is inadmissible. Natural science was able to develop freely in the sixteenth century only when it abandoned occult explanations. Similarly, the Darwinian revolution of the nineteenth century was so impressive because it sought naturalistic explanations for biological phenomena.

 

There is a second meaning of naturalism, which is as a generalized description of the universe. According to the naturalists, nature is best accounted for by reference to material principles, i.e., by mass and energy and physical-chemical properties as encountered in diverse contexts of inquiry. This is a nonreductive naturalism, for although nature is physical-chemical at root, we need to deal with natural processes on various levels of observation and complexity: electrons and molecules, cells and organisms, flowers and trees, psychological cognition and perception, social institutions, and culture. We cannot at this time reduce the concepts and explanations of psychology, economic politics, sociology, or anthropology to physics and chemistry, but need to leave room for naturalistic explanations on various levels of complexity.

 

But to so argue does not entail "spirit" or "purpose" in nature, and least of all a divine being for which there is insufficient evidence. The big-bang theory in physics and astronomy is a useful hypothesis introduced to explain a receding universe; it does not imply a creator or designer. To do so is to leap outside of the naturalistic universe. Thus, naturalists are skeptics, atheists, or agnostics about the God question; they reject the existence of the "soul" or belief that it survives the death of the body.

 

The philosophy of materialism had been developed historically prior to the emergence of modern science. It was attacked by some philosophers because it seemed based on purely abstract metaphysical speculation. Today, it is possible to defend the above form of naturalism, i.e., nonreductive materialism, on empirical scientific grounds. Naturalism thus provides a cosmic interpretation of nature. The universe is basically physical-chemical or material in structure, it is evolving in time; human life is continuous with other natural processes and can be explained in terms of them. To defend naturalism today is to say something significant, for it is an alternative to supernaturalism, which is, in the last analysis, based on a literature of faith and piety, supported by powerful religious institutions, and is unsupported by scientific evidence. It is time, in my view, that scientists defend naturalism forthrightly as the most appropriate generalization of what we have discovered about nature, without retreating into neutral agnosticism or blind faith.

 

Third, naturalism has an ethical dimension; for it relates human values and principles to the desires, interests, and needs of human beings. The critics of naturalistic ethics attempt to derive ethical values and principles from theological premises. Naturalistic ethics, by contrast, rejects the idea that you have to believe in God in order to be moral. If there is no evidence for a divine plan in the universe at large, then humans are responsible for their own destinies individually and socially. We have the opportunity to give life new meaning without mythological illusions, and to achieve a better life here and now. Naturalistic humanists believe that, although our ethical values are relative to human experience, some degree of objectivity is possible in ethics without depending on purely subjectivistic caprice. They maintain that it is possible to reconstruct our ethical values in the light of rational scientific inquiry.

 

The new critics of Darwinism properly perceive that, if the implications of Darwinism are fully accepted, this would indeed mean a basic change in our outlook of who we are, what we are, and also how we ought to live. Darwin's "most dangerous idea" is that natural selection and other causal factors provide a more adequate explanation for the descent of humans than the postulation of divine fiat or design. The efforts to re-crucify Darwin now underway, in my judgment, are motivated by fear. I submit that it is important that scientists and skeptics defend naturalism, not only as a method of inquiry, but as a scientific account of the cosmos and our place within it, and the basis for a new humanistic ethics appropriate to the world community. "No deity will save us; we must save ourselves," says Humanist Manifesto II. To realize this and accept it with courage could be the harbinger of a new, creative, moral future for humankind.