Answer:
Although Darwin’s theory is often described as the theory of evolution by natural selection, most commentators recognize that common ancestry (the idea that all organisms now alive on earth and all present day fossils trace back to one or a few “original progenitors”) is an important part of the Darwinian picture. What has been less explored in Darwin studies is how these two parts of Darwin’s theory – common ancestry and natural selection are related to each other. Ernst Mayr and others have noted that they are logically independent. But this leaves open how the two ideas are evidentially related. How does common ancestry affect the way in which evidence concerning natural selection should be evaluated? And how does natural selection affect the way in which evidence concerning common ancestry should be evaluated?
