An even more impressive demonstration is the existence of ring species: https://en.wikipedia.org/wiki/Ring_species https://en.wikipedia.org/wiki/Ring_species H

An even more impressive demonstration is the existence of ring species: https://en.wikipedia.org/wiki/Ring_species https://en.wikipedia.org/wiki/Ring_species Here, you have a population whose geographic range is in the shape of a ring. Say, around the base of a mountain range. Members of the species may display some regional variation, but they can interbreed with their nearby kin. At some point on the ring though, there is a break. Here, regional variations will have accumulated to the point where the members are not able to interbreed and you have what appears to be two distinct, if similar, species. Only by following the line of population the long way around the ring do you find that the populations are still connected and actually the same species.