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 ...
