There isn't much debate on this anymore in biology - practically every important evolutionary biologist accepts that speciation is driven by natural selection.

There isn't much debate on this anymore in biology - practically every important evolutionary biologist accepts that speciation is driven by natural selection. Of course other factors matter too, like goegraphic separation, and so forth; they can provide an opportunity for natural selection to drive changes between groups, that when they grow large enough become a difference in species. But it is natural selection that creates those differences. There is a small minority that think otherwise.