Friday, November 20, 2009

Chinese Challenge Out of Africa

When we come to the issue of the antiquity of mankind, the present consensus puts it back around 120,000 plus years for an African genesis of modern humanity. It has been accepted for about twenty years.

In this item, the Chinese have dug up the beginnings of a challenge to that proposition.

We are fairly sure that totally modern man was on the ground by 70,000 years ago. What I mean by that is that it would be possible to plug him into the modern world with the proper educational inputs. Art work shows up and complex tools are now been made.

The point is that somewhere a population transitioned into the necessary skill set. My own preference is that this took place in the tropics around Indonesia. That is not important because when the transition took place, mankind commenced operating as a clan unit rather than as a small family unit. That immediately allowed a rapid population expansion back over all prior human populations that surely saw extinctions and cross breeding with the indigenous populations.

The clan structure allowed greater populations and this overwhelmed the smaller populations. Imagine if the Australian Aboriginals were forced to intermarry with the present Australian population. Their traits would disappear in several generations because of numbers alone.

Primate range expansion out of Africa was a constant rather than been exceptional. More importantly the human like primate had one other very effective trick. They engaged in war. This meant that two adjacent tribes actively raided each other for the purpose of killing off (and eating) that tribes males and capturing women into their tribe.

This meant that human gene exchange was wonderfully accelerated. The advent of the social structure of the tribe permitted much larger combat groups than could be sustained by any other primate group, and any that may have existed similar to the remnant aboriginals would have been overwhelmed genetically by numbers. Species uniqueness likely kept some primate lines from been submerged but at the price of extinction.

Chinese challenge to 'out of Africa' theory

The discovery of an early human fossil in southern China may challenge the commonly held idea that modern humans originated out of Africa.

Jin Changzhu and colleagues of the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, announced to Chinese media last week that they have uncovered a 110,000-year-old putative Homo sapiens jawbone from a cave in southern China's Guangxi province.

The mandible has a protruding chin like that of Homo sapiens, but the thickness of the jaw is indicative of more primitive hominins, suggesting that the fossil could derive from interbreeding.

If confirmed, the finding would lend support to the "multiregional hypothesis". This says that modern humans descend from Homo sapiens coming out of Africa who then interbred with more primitive humans on other continents. In contrast, the prevailing "out of Africa" hypothesis holds that modern humans are the direct descendants of people who spread out of Africa to other continents around 100,000 years ago.

The study will appear in Chinese Science Bulletin later this month.

Out of China?

"[This paper] acts to reject the theory that modern humans are of uniquely African origin and supports the notion that emerging African populations mixed with natives they encountered," says Milford Wolpoff, a proponent of the multiregional hypothesis at the University of Michigan.

Others disagreed. Erik Trinkaus, an anthropologist at Washington University in St Louis, Missouri, questioned whether the find was a true Homo sapiens.

"You need to keep in mind that 'Homo sapiens' for most Chinese scholars is not limited to anatomically modern humans," he says. "For many of them, it is all 'post Homo erectus,' humans."

Chris Stringer of London's Natural History Museum said that it was too early to make far-reaching conclusions. "From the parts preserved, this fossil could just as likely be related to preceding archaic humans, or even to the Neanderthals, who at times seem to have extended their range towards China."

The present analysis of the mandible focused almost exclusively on determining the fossil's age. The researchers said a follow-up study would give a more complete treatment on what exactly the find represents.

1 comment:

Unknown said...

I myself would tend---*provisionally*, for the nonce, pending further specific DNA evidence from this find, plus possible future discoveries---to side with both Chris Stringer and Erik Trinkaus. *IF* I'm not mistaken, Chinese anthropologists and archeologists do (rather disturbingly & semantically-problematically) tend to call "human" various (archaic) species and subspecies, such as Heidelbergensis, which are nonetheless NEITHER genetically NOR anatomically identical with modern Homo Sapiens Sapiens. My intuitive sense---again, n.b., provisional---is that this fossil jaw is that of a Heidelbergensis or other relatively recent common ancestor of both Neanderthals and Modern Humans. And while this *could* still be integrated into a multi-regional (or "candelabrum") model, separate, multi-regional *convergence* to so *close* an allelic overall identity as Modern Humans (yet due, ex hypothesi, to not-inconsiderably *different* local (regional) environments (i.e., having merely the current range of allelic difference and vaiability, rather than considerably *more*)) has always intuitively seem rather implausible to me...

What needs to be attempted, rather obviously to me anyway, is to seek to obtain ancient DNA from this jaw fossil, reconstruct it, and compare it both to the Modern Human genome as well as Svante Pääbo's recently completed reconstruction of the Neanderthal genome. The genetic-mutation clock, plus whatever commonalities are shared, as well as specific genetic differences (in terms both of protein-coding genes as well as their respective genetic-*switches*) should help tremendously in falsifying (or corroborating, as it may turn out, though I'm dubious) the conjecture that this fossil jaw find itself falsifies (or at least calls for significant revision in) the "Out of Africa" model. But, again: Let the facts fall where they may, and truth will-out. I URGE specific genetic investigation of this jaw-fossil by an international team (to prevent Chinese nationalist motivation to somehow fudge the results of such a study...).

In any event, this is still, of course, an important find. Let's hope proper investigative genetic study of it commences a.s.a.p.