The theory of evolution asserts ' that evolution has occurred and explains how it occurred. Biological evolution is a fact established beyond reasonable doubt. Living beings descend from other organisms more and more different as we go farther back into the past. Our ancestors of many millions of years ago were not human. We are related to the apes and other animals by common ancestry. Biological evolution is a fact established with the same degree of certainty as the rotation of the planets around the Sun or the roundness of the Earth.
The theory of evolution explains, on the basis of scientific evidence, how evolution happened. For example, scientists explain the functional organization of organisms as the result of natural selection. In a similar way, scientists use gravity for explaining the motions of the planets. Many details of the explanation (for example, whether the rate of change is more or less jerky) are debated by scientists, and some views change time. Similarly, scientist have changed from Newtonian mechanics to relativity theory as a better explanation for the planets' movements.
No biological concept has been more extensively tested and more thoroughly corroborated than the evolutionary origin of living organisms through millions of years of descent with modification. Moreover, nothing in modern biology makes sense except in the light of evolution.
Many religious people accept the fact of evolution. It is possible to admit that God is creator of the world without denying biological evolution, as it is possible to accept that a human being is a creature of God without denying that he has developed from a fertilized egg and embryo by natural processes.
To claim that the statements of Genesis are scientific truths is to deny all the evidence. To teach such statements in the schools as if they were science would do untold harm to the education of American students, who need scientific literacy to prosper in a nation that depends on scientific progress for national security and for indi-vidual health and economic gain.
The Council of the National Academy of Sciences has declared that "religion and science are separate and mutually exclusive realms of human thought whose presentation in the same context leads to misunderstanding of both scientific theory and religious belief."
Scientific reasoning and religious belief are distinct modes of thought. Let science and religion follow their separate courses. That is the American way, and only thus will rationality and common sense survive in our nation.
Ayala is professor of genetics at the University of California, Davis, 95616.