Molecular Genetics and the Foundations of Evolution

MOLECULAR GENETICS AND THE FOUNDATIONS OF EVOLUTION BERNARD D. DAVIS* In the century since Darwin developed his theory, largely on the basis ofcomparative morphology and paleontology, genetics and comparative biochemistry have provided a great deal of further support. And in a dramatic further advance molecular genetics has now yielded a new, more direct kind of evidence for evolutionary continuity, extending from bacteria to man. Indeed, unless we assumed that continuity the study of molecular genetics in bacteria would not help us to understand human cells. Yet various groups remain skeptical, for various reasons. Religious fundamentalists in die Judeo-Christian tradition object that the evolutionary view ofman's origin destroys an indispensable basis for morality. Extreme egalitarians have difficulty with the implication that the genetic diversity within each species, on which natural selection depends, must include mental (as well as physical and biochemical) traits in man. Some literary people, following the line of Arthur Koestler, falsely ascribe to science the goal of discovering absolute truths, and they then criticize evolution for failing to meet that goal [I]. And while a distinguished philosopher of science, Karl Popper, accepted evolution as a fact, he questioned whether Darwin's theory (even in its modern, neo-Darwinian version) meets the criterion that he has proposed for distinguishing a scientific from a metaphysical theory: the ability to generate falsifiable (i.e., testable, refutable) predictions [2]. Popper has now conceded that Much of this material, with more emphasis on its philosophical aspects, appears in a related paper: B. D. Davis, Molecular Genetics and the Falsifiability of Evolution, in E. Ullmann-Margolit, ed., The Kaleidoscope ofScience: Israel Colloquium Studies in History, Philosophy , and Sociology of Science, Vol. 1. Atlantic Highlands, N.J.: Humanities Press, 1984. ?Bacterial Physiology Unit, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115.© 1985 by The University of Chicago. AU rights reserved. 0031-5982/85/2802-0422$01.00 Perspectives in Biology and Medicine, 28, 2 ¦ Winter 1985 | 251 his criterion was too rigid [3, 4], but unfortunately creationists have continued to draw support from his original position [5].1 A recent poll of a representative sample of Americans [6] illustrates die extent of resistance to the theory of evolution: 44 percent of the respondents believed in the special creation ofman occurring within the past 10,000 years, two other groups conceded a longer time scale or else accepted the theory ofa directed evolutionary process, and only 9 percent accepted the scientific conclusion that our species has evolved by undirected natural selection. Though this result is discouraging it is not hard to understand. Scientific ideas on man's origin are relatively recent, while religious ideas carry the weight oflong tradition, have much more emotional appeal, and offer a simpler basis for a moral consensus. No wonder so many people find these ancient, poetic myths about man's origin more credible and more satisfying. Nevertheless, since the question of the origin of our species is a question of biology, only objective scientific inquiry, divorced from moral preferences, can provide an answer that corresponds to reality. And since nature has the last word on such questions it is hard to doubt that the scientific answer will ultimately prevail. But "ultimately" may be a long way off; for although liberal religion is primarily concerned with questions of value, and has given over to science its earlier function of also trying to explain the world ofnature, that is not true ofall religions. Meanwhile, the tensions between science and myths are likely to become worse, as advances in genetics, neurobiology, and sociobiology further contradict treasured preconceptions—political as well as religious— about human nature. Evolution is thus central to our attitude toward reality and to our assumptions about human nature. It is therefore essential, for the future harmony of our society, to try to teach the subject more effectively. In most of its development evolutionary biology has depended on morphological homologies, both in the fossil record and among living species; but this approach has not revealed the continuum of transition forms between species that Darwin predicted. Moreover, while he expected further research in paleontology to fill in the gaps, we no longer entertain that hope. But now, at last...