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.

[Minimalist]

Clarification....sort of....from the author.

Damned reporters!


http://www.nature.com/news/2010/101231/f...0.700.html

According to the paper, the teeth cannot be conclusively identified as belonging to a particular species of human, whether Homo sapiens — the first modern humans — Neanderthals, or other humans. But the press release and some of the articles that drew on it state that the teeth are evidence that Homo sapiens lived in the Levant as early as 400,000 years ago.

Followed by this Q & A between Nature.com and Gopher.

Do the teeth that you found in Qesem Cave really provide evidence that Homo sapiens did not evolve in Africa?

We don't know. What I can say is that they definitely leave all options open. There's been a tendency for people to get so accustomed to the "out of Africa" hypothesis that they use it exclusively and explain any finding that doesn't fit it as evidence of yet another wave of migration out of Africa.

Were you surprised by press reports making claims that didn't appear in your paper?

I told all the reporters I spoke to, to be very cautious what they wrote. But that's what happens. [Gopher also defended the press release as being worded "more sharply" than the paper but that "it was not incorrect"]

(The second answer is fascinating.)

Also today comes this announcement.

http://www.pasthorizons.com/index.php/ar...ld-adapted

Researchers have reported in the Journal of Human Evolution that the long held belief that the Neanderthal nose was a result of adaptations to extreme cold may not be all it seems.

So the beat goes on.

[Welsh cake]

It would answer the question of why humans ever left "Africa" in the first place.

And the ever changing climate variation that the Sahara desert has undergone in the last several hundred thousand years does not?

[Minimalist]

Not really, no. For one thing, if humans were in the Sahara then to get out of Africa they would have to cross the Nile...not an easy task for people who lack the concept of boats or at least rafts. Second, much of human development is supposed to have come from the Tanzania region which would at least get them on the right side of the Nile but is a bit too far south to be considered the "Sahara." Third, even today as the Sahara creeps south, people do not move. They sit there and watch their farmland turn to sand unless a war breaks out and then they become refugees.

The whole question of how and why people migrate is another fascinating topic, though.

[Anomalocaris]

1. There is no reason i know of to suppose the Nile was continuously a perennial swift flowing river impassible to wadders or primitive swimmers with primitive swimming aids like innflated animal bladders during the entire late pleistecene period. If the river nearly ran dry during just one particular dry season during the last 100000 years, that's enough.

2. Sahara is just an eye catching manifestation of the rainfall patterns throughout tropical and subtropical Africa. As change sahara so change much of the rest of Africa. So changes in sahara could mean large scale climate and ecological upheaval in tanzania and the afar triangle, sarengeti, etc. So change in sahara can be used to explain acute migration pressure on people living outside sahara.

3. Modern people who don't move are farmers. Farmers are by necessity culturally sedentary Their disinclination to move can't be projected onto hunter gatherers 60000 years ago, when ooa migration is thought to have happened. Hunter gatherer cultures are by necessity mobile.

4. The OOA hypothesis call for only one or small Number of small bands of HSS to make it out of Africa, not mass migration requiring similar demonstration of mobility for large groups. That makes it naturally inappropriate to use typical behavior of large groups of people, like those who didn't move in response to encroaching sahara, to exclude certain behavior on the part of Ooa sized groups.

[downbeatplumb]

Stone tools resembling those by 'modern humans' found outside of dated to be 50.000 years older than they should be.

http://www.bbc.co.uk/news/science-environment-12300228