Futuyma: It sometimes does but not

Futuyma: It sometimes does but not always. A great deal of evolution by natural selection can happen without the formation of new species. Natural selection is only the process of adaptation within species, and we see many examples of that. Under some circumstances natural selection does play a role in the origin of new species, by which I mean a splitting of one species lineage into two different lineages that do not interbreed with one another — for example, the splitting of one ancestral primate lineage into one that became today’s chimpanzee and the other that became the hominid line resulting in our own species. The process of splitting and becoming reproductively isolated, that is, incapable of breeding with one another, can often involve natural selection but perhaps not always.