The Out of Africa Crowd May Shit A Brick

[Anomalocaris]

Now, it seems to me that there are only three answers to this.

One. HSS and HNS did interbreed and were capable of producing fertile offspring ( no "ligers" here!) which accounts for the genetic mix detected...and which calls into question those definitions of "species" which hold that a species is a group capable of bearing fertile offspring. In fact, it suggests that HNS and HSS are not different "species" at all but more like what we call "racial" types.

You definition of "species" needs updating. A population must have more than the physical ability to interbreed and produce fertile offspring to be a single species. It must also exhibit natural mating behavior that would promote the frequent exchanging of genes within the whole population to qualify as a single species.

So take for example the African Elephant. There are two species of African elephant still in existence: Loxondonta africana and loxonodonta cyclicotis. They look similar, they can physically interbreed and produce fertile offsprings. But they are two different species for two reasons. The first is genetic. Although they can interbreed, We can tell that the last common ancestor to make major contributions to the gene pool of both africana and cyclists lived 2 million years ago. Since then any mating has not contributed much to keeping the two gene pools equilibrated. The second is behavioral. Although the offspring of mating between africana and cyclicotis are technically fertile, they are morphologically sufficiently different from pure blooded africana and cyclicotis that they have low probability of succeeding in getting mates. So although biologically fertile, they effective fertility is very low.

The same appears to apply between Homo Neanderthalensis and Homo Sapiens. Genetically the last common ancestor to contribute much to both populations seems to have lived 600,000 years ago. Later interbreeding has not succeeded in homogenizing the gene pools. Neanderthals and sapiens are morphologically different. Perhaps more importantly, their respective offsprings seems to develop differently, suggesting the rearing of results of interbreeding using the child raising behavior of one or the other group may not work well in bring the child up to integrate well with the group. So it may well also be that their mating may produce fertile offsprings, but those offsprings rarely mate successfully themselves.

Two. They did not interbreed successfully at all but both descended from a common ancestor ( Homo Erectus? Homo Ergaster?) which possessed these genes and passed them along to both.


Three. They were descended from HE/HErg and still managed to interbreed successfully because the condition of isolation which Darwin proposed gives rise to new species did not exist.

The notion of the hulking, dim-witted, brutish HNS has taken a number of serious hits in recent years. It was a Victorian prejudice that became "common" wisdom. Bottom line seems to be that they were not all that different from HSS.

But I love a mystery. Keeps the brain churning!

They are apparently all that different. It doesn't mean they were dim-witted or brutish, but the barriers to successfully homogenizing a population of both HSS and HNS appears to have been sufficiently formidable such that despite coexistence of thirty thousands years, it never really occurred. Only small percentage of genes may have made it across during all those years. Compare that against what is accomplished within the recognized species of homo sapiens. One would be hard pressed to point to any two modern HSS populations that coexisted for even a few hundred years without significant homogenization of the gene pools, regardless of seemingly colossal cultural and racial prejudice that might exist against interbreeding.