Well, that's where taxonomic hair-splitting below species level comes in. Below that is race/subspecies, of course, and then below THAT comes in behavioural differences within a race (called "ethnicity" in humans, or tribes). A black American is definitely of a different ethnicity than someone from Nigeria (or Australia, for that matter) even though they might share a more recent common ancestor with each other than with any other groups of humans, and the black American might seem behaviourally "white" in the Nigerian's eyes.

Yeah, this happens in other species as well, but it's not talked about much. We just mostly get the kindergarten view of evolution, as being caused by "random changes" caused by "geological separation" (mountains and oceans) on the timescale of geology, rather than biology. But, as Darwin noted, intra-species competition is probably more important than any other kind of pressure exerted on a species (ie, its social condition puts more evolutionary pressure on a population than predators, disease, climate, etc.) A change in behaviour might turn some off, and attract some, within a population, and then, when the two different groups grow so big and can't stand living with one another any more, migration happens. Like a guy named Abraham taking his family and like-minded sky-god worhshipping monotheistic friends across the desert to get away from people who were polytheists. The problem comes when an animal has no more room to spread and for new populations to claim new territory ...

And do note that domestication experiments indicate that changes in behaviour patterns are often accompanied by changes in appearance (eye and hair colour, for instance.)

Well, that's where taxonomic hair-splitting below species level comes in. Below that is race/subspecies, of course, and then below THAT comes in behavioural differences within a race (called "ethnicity" in humans, or tribes). A black American is definitely of a different ethnicity than someone from Nigeria (or Australia, for that matter) even though they might share a more recent common ancestor with each other than with any other groups of humans, and the black American might seem behaviourally "white" in the Nigerian's eyes.

Yeah, this happens in other species as well, but it's not talked about much. We just mostly get the kindergarten view of evolution, as being caused by "random changes" caused by "geological separation" (mountains and oceans) on the timescale of geology, rather than biology. But, as Darwin noted, intra-species competition is probably more important than any other kind of pressure exerted on a species (ie, its social condition puts more evolutionary pressure on a population than predators, disease, climate, etc.) A change in behaviour might turn some off, and attract some, within a population, and then, when the two different groups grow so big and can't stand living with one another any more, migration happens. Like a guy named Abraham taking his family and like-minded sky-god worhshipping monotheistic friends across the desert to get away from people who were polytheists. The problem comes when an animal has no more room to spread and for new populations to claim new territory ...