This is interesting because it provides a mechanism for speciation that doesn't involve sequestration in a lost valley or something like that: in an already est

This is interesting because it provides a mechanism for speciation that doesn't involve sequestration in a lost valley or something like that: in an already established population, once you have a herd or tribe that has translocated chromosomes floating around, that subgroup has much-lowered chances of (successful) mating outside the subgroup. That, in turn, means that any beneficial mutation that arises by random chance is kept "in-house", as it were, and refined in the crucible of inbreeding, while the subgroup begins to succesfully outcompete the rest of the local population—and that local population can't acquire the beneficial mutation because of the breeding problem. Keep in mind the very large numbers we're dealing with when we talk about speciation events. All of recorded human history is perhaps six or eight thousand years, but a hundred thousand years is a short time frame on an evolutionary scale; so even an incredibly rare mutation will happen many times.