by Francisco Ayala
Introductory Essay by Peter MJ Hess
By now, the validity of the scientific approach to understanding the physical universe ought to be axiomatic. Yet it is still challenged. One of the more trying challenges is to the evolutionary explanation of the diversity of life, a question that should have been settled decisively in the previous century. In Darwin’s Gift, Francisco Ayala does a fine job of approaching this problem forthrightly with candor, erudition, and wit.
In the preface Ayala enunciates his book’s three aims: (1) To reaffirm that science and religious beliefs need not stand in contradiction; for people of faith, they ought to stand in a relationship that is mutually motivating and inspiring. (2) To inform people of faith that science is here to stay and that scientists continue to persist with integrity in their endeavor to advance human knowledge about the world. (3) To assert that science in general – and evolution in particular – are consistent with belief in God, whereas creationism (including so-called “intelligent design”) is at least in tension with it.
Rehearsing his signature claim, Ayala explains that Darwin’s articulation of evolution completed the great upheaval begun by Copernicus, and that together the cosmological and the biological revolutions ushered in modern science. Ayala argues that Darwin treasured his idea of natural selection over and above evolution because it offered a cogent scientific answer to the argument from design made most prominently by William Paley (he explores this in depth in his final chapter). He shows how Darwin used natural selection to account for the adaptive organization of organisms, and how such factors as hereditary variation, mutations, and geographical isolation embodied the interplay of chance and necessity that gave birth to the “tangled bank” of life.
The core of Ayala’s case for evolution lies in chapters 5-7, where he shows how Darwin’s insight has been reconfirmed over the past 150 years by the fossil record, anatomical homologies, embryonic development, biogeography, and numerous other strands of consilient evidence. Ayala’s outline of human evolution shows how Darwin’s theory of the “descent of man” has been confirmed by developments in paleo-anthropology and allied disciplines. Further evidence of evolution comes from sciences that arose or matured after Darwin’s death, such as microbiology and genetics.
Later, Ayala turns to the arguments adduced by proponents of “intelligent design,” arguing that they lack scientific cogency and religious merit. He adroitly exposes the philosophical naiveté of the claim that “evolution is only a theory,” showing how this misunderstands how theories operate in science. Ayala dispatches creationism’s favorite conundrums of the evolution of the eye, the bacterial flagellum, and blood clotting, explaining how each of these easily yields to evolutionary explanation.
Theologically, his critique of creationism focuses on the implication that God is responsible for “the dysfunctions, oddities, cruelties, and sadism that pervade the world of life” , a problem avoided by asserting that God creates through the secondary cause of evolution. Moving beyond biology in his final chapter, Ayala contends that science and religion are complementary ways of knowing, directing us to the ongoing integrative work of evolutionary theology.