10,000 Year Explosion: How Civilization Accelerated Human Evolution [Paperback]

The Past Is A Foreign Country, February 7, 2009
By William Holmes "semloh2287" (Portland, OR USA) - See all my reviews

Despite the complexity of the subject, "The 10,000 Year Explosion" is clearly written and compellingly argued. The book is devoted to refuting the idea that human evolution stopped 10,000 or 50,000 years ago, as some have argued. Rather, humans are constantly adapting to diseases, cultural innovations, and myriad other changes in the environment. As Cochran and Harpending point out in the Overview to their book, "humans have changed significantly in body and mind over recorded history. Sargon and Imhotep were different from you genetically as well as culturally."

At some level, the idea is plainly correct. Sickle cell anemia, for example, results from an adaptation to malaria. Those who had the gene were more likely to live long enough to have offspring, so the genes that code for malaria resistance are much more frequent in populations originating from areas where malaria has been historically common.

The same principle explains why the New World's inhabitants were almost completely wiped out by diseases imported from the Old World--by some estimates, mortality approached 90% of the pre-1492 population of North America and South America. The denizens of the Old World had been pastoralists and farmers much longer than their New World counterparts, and so had been exposed to a host of nasty diseases that originate from domesticated animals (e.g., smallpox). The farmers who were lucky enough to have a genetic adaptation that could resist the diseases passed the adaptation along to their offspring, and over hundreds or thousands of years the genetic defense swept through the whole population. By the time Columbus reached the New World, he and has compatriots had evolved to resist the Old World's diseases. In the New World, the Native American population had turned to agriculture relatively recently and didn't have the same suite of domesticated animals as the inhabitants of the Old World. Native Americans had evolved no genetic defenses against the diseases brought by the Europeans, and millions died in the space of a few decades. (The tables were turned on the Europeans who ventured into Africa, who were genetically ill-equipped to deal with tropical diseases like malaria.)

Cochran and Harpending's discussion of the Ashkenazim is bound to be more controverial and disturbing. The authors argue that, during the Middle Ages, the Ashkenazi Jews were, for various cultural reasons, a genetically isolated population that could make a living only in certain demanding careers, such as money lending and asset management. All of these occupations rewarded great intellectual ability, so over a period of hundreds of years, the Ashkenazi Jews became smarter on average than other Europeans. (According to the authors, the average IQ of the Ashkenazi Jews is 112, about three quarters of a standard deviation above the European mean.) This pushed the normal distribution of IQ scores among the Ashkenazi to the right, so the Ashkenazi were rewarded with a disproportionate number of geniuses relative to the size of their population. As further support for their hypothesis, the authors point out that the genetic diseases like Tay-Sachs that are associated with the Ashkenazi population seem to be errant expressions of genes that enhance the performance of the brain and central nervous system.

Of course, many of us become very uncomfortable when genetics seems to suggest that one human population might, on average, be more intelligent than another. Arguments about the alleged superiority of one group over another have been used to horrible effect in human history. But the authors are optimists, not racists. Pointing out that there is a unique genetic adaptation among the inhabitants of the village of Limone sul Garda that greatly reduces the risk of coronary disease, the authors argue that "some of the results of history's experiments may even aid us in more ambitious efforts aimed at increasing human life spans and cognitive abilities." Fine up to a point, but we must always be wary of the enthusiasms of those who would twist such hopeful conclusions into an argument for a new form of eugenics.

The thesis of this book is that the changing environments encountered by human populations since the original excursion out of Africa ~50,000 years ago - and more recently through the introduction of agriculture, have led to substantial and differential genetic changes in various human populations. Therefore, to understand the deep history of humanity, we need a combined cultural-genetic analysis in which each component couples to the other.

Key ideas include:

* The evolved disease-resistance of Europeans + their diseases effectively destroyed the Amerindian populations of North and South America, which led to a relatively easy colonisation by quite small forces. Compare the European inability to colonise Africa, rich in its own diseases to which the indigenous Africans were far better adapted: *they* didn't die off.

* The spread of the original Indo-European speakers from their Pontic-Caspian Steppe homeland was, the authors argue, driven by a lactose-tolerating mutation which allowed those nomadic invaders to consume milk. This is a far more efficient energy source than slaughtering cattle, supporting five times as many warriors per square kilometre.

* And then the explanation of the superior intelligence (~0.7 std. dev.) of the Ashkenazi Jews due to strong selective pressure in their taxation, money lending and management niche over the last thousand years in northern Europe ... and the price in genetic diseases of the nervous system they pay for their IQ-boosting mutations.

I suspect the enemies of applying evolutionary theory to human development will have to die-off before the paradigm gets decisively shifted, but to an honest evolutionist, the approach of this book cannot be faulted.

We are at the earliest stages of differential genetic analysis, and I expect that the bubbling ideas and historical scenarios outlined in such a clear and entertaining way in this book will be substantially developed and refined in the coming years.

the authors point out that the human genome has changed rapidly - in fact over the past 10.000 years much more rapidly than possible before.

Possibly European history was aided by the Neanderthal genome - but this is still quite speculative and more evidence should be drawn out by recent sequencing of Neanderthal genome. However, more interesting is the change in lcatose tollerance which has aided the Indo Germanic dominance from Europe to India. They were settlers how could digest the milk - this explains why local population was much slower at adaptation.

Interestingly they make the point that European jews may habe been bread for intelligence and thus aquired some genetic deseases like Tay Sachs. This sounded very convincing.

some futher analysis is missing. No treatment of the Flynn effect. Not quite sure whether humans would have actually acquired higher intelligence from North to South - the authors dont give definite answers, but this could not be done given the evidence there is. So they very much manage to stay away from rasism and just look at facts.