Thursday, August 17, 2006

Before the Dawn

Is a fascinating and informative book that brings together NYT science reporter Nick Wade's vast work on human history, focusing most intensely on the human story from 50,000 to 5,000 years ago. If it's not on your reading list, at least let me pass on a few of the most salient points (and my thoughts on and additions to them) that stick in my mind without need for reference:

- Neanderthals, who developed dinstinctly from their African cousins 127,000 years ago, likely did not interbreed with the homo sapiens as the latter pushed them into extinction over a nearly 20,000 year long encroachment into Europe. Given the small size and bellicosity of human groups at the time, if minimal interbreeding did occur, it was probably in the form of female Neanderthal captives.

- Neanderthals, physically stronger and enjoying equivalent and in some cases higher encephalization quotients than homo sapiens, are posited to have lost out due to a lack of syntax development in language (if they could speak at all). Complex communication was our ancestors weapon of mass destruction (and a crucially important part of human evolution).

- Modern humans are all descended from a single Adam and a single Eve (although the two come from different time periods; Adam estimated to have lived 59,000 years ago, Eve 150,000 years ago).

- Hobbes knew a lot more about human nature than Rousseau. The annual mortality rate suffered in war for our nomadic ancestors was in some cases as high as 30%--contemporarily, it is around .5%. In concert with our budding pacificism, our skulls have undergone gracilization and become more delicate. We're just not as pugnacious as we used to be.

- First-degree murder is not a uniquely human activity. Chimps do it all the time, preferring at least a three-to-one advantage, so that two of the assaulters can restrain the victim while the third pummels him to death.

- Human populations continue to evolve disparately from one another. Wade points out that it is conceivable that sometime in the future the divergence will be so substantial that various human groups will be unable to mate with one another and the homo sapien community will split into different species.

Microcephalin, which appeared for the first time around 37,000 years ago, is now carried by over two-thirds of Europe and East Asia. In sub-Saharan Africa, by contrast, from 0% to 25% of members of various populations carry it. ASPM, another brain gene, popped up in either the Middle East or Europe only 6,000 years ago, with about half of the population in these regions carrying it. It's less common in East Asians and virtually non-existent in sub-Saharan Africa. Thus far, the genes are known to determine brain size.

Given the increased need for long-term planning through gathering food for the winter, the increased stress of having to deal with rougher climates, and having to battle perpetually with Neanderthals in Europe and homo erectus in East Asia, it is not surprising that higher IQs and EQs are generally found in human populations that had to deal with these novel challenges that weren't faced in Africa.

- Babies look non-descript as a defense mechanism against potentially angry fathers who might refuse to care for the child or even kill it if it appeared to be the handiwork of zoot suiter. Further, I would speculate, the generic appearance of human infants made non-parental females (and do a lesser extent males) more likely to provide care and refrain from overly preferential treatment of some youngsters in the absence of the biological parent.

- Genghis Khan probably has more living descendants than anyone else in recorded history. Days after finishing Wade's book, I read a biography on Khan and it comes as no surprise that this illiterate nomad of the Central Asian steppes has inherited 8% of the former Mongolian empire (the largest the world has ever known). While Khan was generous in allowing his top generals to have women and treasure from the plundered communities that the Mongols devastated (customarily they slaughtered or enslaved all men as well as the elderly, often times after agreeing to accept a peaceful surrender), Khan got first dibs. His sons, including his inebriated successor, Ogodei, carried on the tradition.

- Geographical determinism inevitably leads to biological determinism, as evolutionary pressures begin acting upon disparate groups as soon as they separate, although the sequence may largely work the other way around. That is, settled communities that had abandoned nomadic existence predate agriculture by as much as 8,000 years. Sedentary life, seemingly so superior now, required substantial adaptations; namely living in large groups and having to trust strangers, as well as the development of a sense of trust and reciprocity. Agriculture was a chance discovery following the existence of human settlements.

Generally, humans have probably still not developed sufficiently to an urban existence, and this ability likely varies genetically.

The last 50,000 years of human existence has been characterized by disparate human populations interbreeding almost exclusively. Add in genetic drift and founder effects, and we have a very diverse human community. This suggests genetic diversity is undoubtedly a factor in the different behaviors, physiologies, temperaments, cognitive abilities, ad infinitum that we see displayed in various human populations today.

Much more in the book. It's worth the time if you can spare it.

(Human biodiversity2)


JSBolton said...

Wade says:..."Since all occurred after the dispersal from Africa, the alleles that cause them are present to a different extent in different populations. Human diversity therefore cannot be a purely cultural phenomenon, as many social scientists sometimes seem to believe. It has to have a genetic component too." This is from p.171, referring to alleles implicated in brain size and IQ.

Anonymous said...

Wade is a human realist right under the noses of the most unrealistic media chamber in the country.