K9APE’S BOOKSHELF
Sheldon L. Epstein
The 10,000 Year Explosion
How Civilization Accelerated Human Evolution
Gregory Cochran & Henry Harpending
©2009 – ISBN 978-0-465-00221-4
The 10,000 Year Explosion is about human genetics and its interaction with events over the last 100 centuries. It also describes some recent advances in Genetic Engineering so that we can begin to understand something about who were our ancestors and who are we. With this information we can speculate about some attributes of our descendents.
The book begins with a hypothesis; namely, that human evolution has accelerated in the past 10,000 years, rather than slowing or stopping, and is now happening about 100 times faster than its long time average of the 6 million years of our existence. Thus, the authors directly confront Stephen Jay Gould who wrote: There has been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilization we’ve built with the same body or brain.
The first 64-pages contain hard plodding text that requires an above-average understanding of genetics to appreciate. Its principal points for present purposes are a) populations in stable environments undergo genetic changes that bring them into equilibrium with their environments, b) human populations over the last 50,000-years have not been in stable environments because of movements out of Africa, into Europe and then across the Earth, c) observable differences in human populations must have evolved rapidly because some alleles§ underlying those differences had strong selective advantages d) our ancestors bred with their Neanderthal competitors and were able to acquire some advantageous Neanderthal traits and e) interbreeding gave humans advantages that led to Neanderthals becoming extinct. All of this –to my mind- is compatible with Darwin’s theory of Evolution.
Thus, the authors reach their first principal conclusion that introgression© is central to the story of human origins and that by 40,000-years ago humans had become anatomically and behaviorally modern – owing in part to genes stolen from their Neanderthal cousins. The advantages gained by humans include talent to innovate, resistance to certain diseases and capability to digest certain foods (e.g. dairy products).
Once past Page 100, the book becomes less theoretical and more practical – or more historical. It starts to describe consequences of a human shift from hunter-gatherer to that of farmer. This shift is described in terms of changes in nutritional requirements and diets as well as social organizations, wealth and gratification needs (e.g. waiting for harvest time). Genetic differences are also identified together with their consequences.
At Page 129, the authors provide a somewhat mathematical treatment of Gene Flow. Individuals with favorable alleles have an inherited adaptive advantage that translates into more progeny. If there are no barriers to travel, then transmission of favorable alleles can be widespread and relatively rapid. On the other hand, barriers to travel (e.g. oceans) cause diverse populations with important genetic differences. One consequence is susceptibility to diseases of foreign populations.
At Page 148, there is a particularly interesting description of the origin of Blue Eyes. According to the authors, there was no such thing as blue eyes as recently as 10,000-years ago. About 6,000-years ago an allele accounting for 75% of the variation in eye color is thought to have first appeared in a Lithuanian village. How it arrived there is not exactly known; but, the authors attribute it to westward migration of Vandals.
Chapter 6, beginning at Page 155, illustrates the effect of expansions as one group contacts and competes with another group – as by war or trade. In such situations, alleles that favor adaptive ability and resistance to certain diseases often determine the successful group. For example, some Native Americans experienced 90% mortality rates because they had no resistance to smallpox, measles, diphtheria, whooping cough, leprosy and bubonic plague. On the other hand, Europeans fell victim to syphilis. But if the Europeans had a genetic advantage over Native Americans, then why did Europeans not succeed in Africa? The authors address that conundrum – partly by proposing that East-West migration was more favorable to them than North-South movement.
The final –and most controversial- chapter is 7 – Medieval Evolution: How The Ashkenazi Jews Got Their Smarts. Ashkenazi Jews comprise approximately 90% of America’s Jewish population and emigrated from largely isolated small communities in Hungary, Poland, Lithuania, Russia and Eastern Europe where arranged marriages prevented assimilation with neighboring Christian populations. As a result, Ashkenazi Jews (the term is a Hebrew word for German) are genetically different from other Jewish populations – such as those from the Middle East and North Africa.
According to the authors at Page 188, Ashkenazi Jews have the highest IQ of any ethnic group known. However, there is a price to pay; specifically, the alleles thought to contribute to higher IQ scores by promoting more neural synaptic connections also play a role in making Ashkenazi Jews more susceptible to Tay-Sachs diseases, Gaucher’s disease, familial dysautonomia and breast cancer.
Regarding the susceptibility to certain diseases, I would insert a word of caution. Ashkenazi Jews constitute approximately 1½% of the American population; yet, have far higher incidences of reported cases of the diseases enumerated above – as well as some others. It is my opinion that a goodly portion of these higher rates for some medical conditions are likely to be an effect of a clustering of Ashkenazi Jews in major cities where there are research-quality hospitals that are capable of diagnosing diseases thought to be Jewish. My research into the incidence rates of certain myeloproliferative diseases thought to be Jewish concluded that high Jewish rates were wholly attributable to population clustering – with a result being that populations in the hinterlands are at serious risk for lack of proper diagnosis.
Returning to the subject of intelligence, the authors state at Page 191 that the average IQ score of Ashkenazi Jews is around 112 or ¾ of a standard deviation above the European mean. As the graphs on Page 192 illustrate, the higher mean translates into an increase in the number of individuals having IQ scores above 2½-sigma. The significance of this is outlined by the authors; but, is better explained in a book titled The Bell Curve by Charles Murray that quantifies how earning capacity is correlated with IQ scores. In any case, the authors fail to state that Ashkenazi Jews are not outstanding when compared by some other metrics – such as sports records – although some individuals have earned recognition for achievements not related to IQ scores.
In conclusion, The 10,000 Year Explosion is a book that I heartily recommend for advanced high school and college students because it combines an analysis of genetics with a study of history and population statistics. For those seeking answers, this book comes up short – if for no other reason than it is only 227-Pages; however, it has an inviting glossary and bibliography. Its real value is in the questions that it raises – and we will be asking these same questions for many years to come.