Paul Clark

A review of The 10,000 Year Explosion: How Civilisation Accelerated Human Evolution by Gregory Cochran and Henry Harpending.

Reviewed by Paul Clark. Originally posted August 2015

This book is not a crude racist tract. The authors are professors of anthropology and their work has garnered praise from fellow academics, scientific journals and the Wall Street Journal. It is well written and cogently argued, with clear and concise explanations of the complexities of genetic change.

Any discussion of the differences between races is bound to be controversial, and this book has been seized upon by people who see it as vindication of their decidedly unpleasant views.[1] I found it one of the most disturbing books I had ever read and embarked on this review in order to explore the issues it raises and see for myself how strong Cochran and Harpending’s arguments are.

Their book includes extended discussion of five hypotheses about genetic differences between ethnic groups. The first two, lactose tolerance and resistance to pathogens, are physiological and should not be controversial.

The same cannot be said of the other three, which propose cognitive and behavioural differences stem from the genetic inheritance of different ethnic groups. The first is increased intelligence that they attribute to interbreeding between early Eurasians and Neanderthals. The second is a predisposition to the ‘bourgeois’ values of hard work and restraint caused by long-term exposure to an agrarian lifestyle. The third is a higher level of intelligence found among Ashkenazi Jews, which the authors attribute to the restrictions their ancestors were placed under in medieval Europe. This review will focus on these three hypotheses.

THE NEANDERTHAL ADVANTAGE

The relationship between Homo sapiens and the Neanderthals has long been a subject of debate, but it is now widely accepted that there was some interbreeding between the two species during the thousands of years in which they coexisted. Recent studies have found Neanderthal DNA in European and Asian populations but not in sub-Saharan Africans.

Homo sapiens first encountered Neanderthals in Europe and the Near East about 40,000 years ago, soon after the exodus from Africa. Cochran and Harpending point out that this is also the time of the Upper Palaeolithic revolution, a sudden transition to modern behaviour characterised by an explosion of creativity in technology, social and economic organisation and symbolic behaviour.

They say that the fact that this great leap forward occurred at about the same time as our first encounter with Neanderthals is not a coincidence. This revolution only happened in Eurasia and, they claim, it is best explained by genetic changes in Eurasian populations. They speculate that this was the result of interbreeding with the large-brained Neanderthals, making Eurasians more intelligent than their stay-at-home cousins in Africa.

This seems credible but highly speculative – indeed Cochran and Harpending admit the latter point. They present their idea as nothing more than a hypothesis, albeit the one that best explains the Upper Palaeolithic revolution.

This raises one question in my mind: sub-Saharan Africans have at some stage successfully made the same transition to modern behaviour, but if Neanderthal DNA was a necessary requirement for this transition, how did they manage it? Whatever the answer to this question, many proponents of the Upper Palaeolithic great leap forward do not believe that there is a genetic explanation at all but point to the technological or cultural developments as more likely causes.[2]

Others argue that the transition to modern behaviour occurred in Africa long before the exodus to Europe and Asia. They cite discoveries like a 70,000 year-old settlement in northern Sudan[3] that is far larger than the Upper Palaeolithic model would predict. Artefacts of a similar age found at the Blombos Caves in South Africa are seen by some (but not by Cochran and Harpending) as evidence of modern behaviour long before the Upper Palaeolithic.[4] And sophisticated 44,000 year-old tools found in southern Africa, including beeswax adhesive and poison-tipped bone points, also undermine the idea of a purely Eurasian great leap forward.[5]

These and other discoveries suggest that the transition to modern behaviour may have occurred in Africa much earlier than the proponents of the Upper Palaeolithic revolution propose. Indeed, it is possible that there was no great leap forward at all and the ‘revolution’ consisted of incremental changes that took place over an extended period.

Cochran and Harpending admit that their Neanderthal hypothesis is speculative. What they don’t say is that the idea that there was a Eurasian Upper Palaeolithic revolution that needs explaining is far from universally accepted.[6] If critics of the Upper Palaeolithic model are correct, their Neanderthal claims are irrelevant.

THE AGRICULTURAL REVOLUTION AND BOURGEOIS VALUES

The second controversial hypothesis is that the agricultural revolution led to genetic changes that have had the greatest effect on the personalities of those populations that have been exposed to agriculture for longest. In particular, the genes of certain ethnic groups tend to make them more hardworking and restrained in their behaviour than others.

Cochran and Harpending tell the story of the spread of agriculture. The cultivation of cereals appears to have started in the Levant around 9,500 BCE and in China and Egypt some 1,500 years later, spreading gradually through Europe after that. They say the Sahara halted the spread of agriculture to sub-Saharan Africa until about 2,000 BCE. Farming arose in the Americas a thousand years later but never developed at all among the Australian Aborigines.

The authors stress the immense changes brought about by the agricultural revolution: a population explosion, the growth of wealthy elites, the spread of disease, changes to our metabolism and our digestive system and changes to our neurotransmitters and serotonin production.

Consequently, they say, evolutionary pressures selected for the bourgeois values of restraint and hard work. Farmers had to learn not to eat their seed corn, no matter how desperate the food situation. The authors contrast this with the behaviour of Bushmen, who have scuppered attempts to turn them into herders by eating all their goats.

Hunter gatherers also never need to work hard. If their bellies are full and their tools are sharp, they have nothing to do. This is not the case for farmers. If they work hard, they can accumulate wealth and save to buy more land and livestock, which will provide them with more reproductive opportunities as their children’s mortality declines. Farmers also have to trade at a profit, which demands sharper minds.

Cochran and Harpending claim that the longer a population has been exposed to agriculture, the more bourgeois values will have been stamped into their genes. One example they cite is ADHD, the alleles for which are almost unknown in China: ‘It is possible that individuals bearing these alleles were selected against because of cultural patterns in China. The Japanese say that the nail that sticks out is hammered down, but in China it may have been pulled out and thrown away.’

Another example is middlemen: they suggest that it is not a coincidence that the ethnic minorities which become middlemen (Armenians, Jews, Lebanese, Parsees, Indians in east Africa and Chinese in south-east Asia) come from populations that have been exposed to agriculture for a very long time.

Whilst superficially convincing, this account contains factual inaccuracies and controversial statements presented as facts. The authors appear to misunderstand the nature of pre-capitalist society and attempt to force their hypothesis onto phenomena which have other, simpler explanations. They also underestimate the importance of culture in influencing behaviour.

Cochran and Harpending’s most glaring inaccuracy is their claim that ADHD has been bred out of the Chinese. In fact it affects up to 5% of mainland China’s schoolchildren.[7] There is evidence that it may be a little less prevalent in Hong Kong than in the USA and diagnosed slightly differently, but these differences are not significant.[8]

Other claims presented as facts are in reality matters of dispute. Agriculture may have been developed in sub-Saharan Africa a thousand years earlier than the authors claim,[9] and there is a considerable body of evidence to suggest that the Australian Aborigines did develop agriculture. This was spotted by the early explorers but ignored by colonists because it did not fit their narrative of the Aborigines as a hopeless race entirely lacking in merit.[10]

In my view the book seriously overestimates the importance of bourgeois values in ancient and medieval agrarian society. Hard work was not seen as the best way to acquire more resources for the simple reason that in static, pre-capitalist societies[11] people believed that the amount of wealth in circulation was fixed and the only way to acquire more was to squeeze it out of someone else.

Where governments were weak, the best way to do this was by acting a ‘stationary bandit,’ to use Mancur Olson’s wonderfully descriptive phrase. A warlord and his armed followers could set up a protection racket among the peasants in their locality and attempt to pillage neighbouring communities. If they added a little rape too, they would doubtless increase their chances of reproductive success. In time they could give themselves aristocratic titles which would help their descendents to keep their ill-gotten gains if and when central authority grew stronger.

Where governments were strong, the best way to acquire wealth would be to ingratiate yourself with your ruler and secure a profitable sinecure that allowed you to milk those under your control.[12]

Nor were the great peasant mass of the population any more keen on hard work. Though there were times when they had to work extremely hard, peasants would put their feet up whenever possible. In what must be among the most in-depth studies of any medieval community, Emmanuel Le Roy Ladurie writes: ‘The people of Monaillou were fond of having a nap, of taking it easy, of delousing one another in the sun or by the fire. Whenever they could, they tended to shorten the working day into half a day.’[13] This doesn’t sound very different from Cochran and Harpending’s description of hunter-gatherers who have nothing to do: ‘They hung out: They talked, gossiped and sang. They were lazy, and should have been. Being lazy made biological sense.’

From the point of view of the peasants, such laziness was entirely rational too. Catholicism, Islam, Hinduism, Buddhism and Confucianism all stressed the importance of social harmony and knowing your place. In most pre-capitalist societies, any attempt to accumulate enough wealth to rise above your station was seen as deeply sinful.[14] It was only much later in Protestant northern Europe that work and the accumulation of wealth became synonymous with virtue and age-old social norms were challenged and eventually overthrown.[15]

Ancient and medieval agrarian societies did contain small proto-capitalist minorities of traders and moneylenders who could and did acquire wealth through hard work. But what did they do once they had acquired enough? For the most part, they turned it into land, stopped working and found an impoverished noble family for their children to marry into.[16] Just about the only people unable to do this were religious minorities such as Armenians, Jews, Lebanese Christians and Parsees.

These people remained trapped in their trading niche because they were religious minorities and so did not have the option of marrying into the landed nobility, not because their agrarian genes predisposed them to bourgeois values. Sometimes it seems that Cochran and Harpending will never settle for the obvious cultural explanation for any phenomenon when it is possible to posit a genetic explanation instead.

The case of the overseas Chinese in south-east Asia is more complex because outside Malaysia and Indonesia they are not a religious minority and the option of integration has not been closed to them in the same way.

The largest overseas Chinese community in the world is in Thailand. The partly integrated Thai Chinese enjoy great prominence in Thai business circles, which, according to Cochran and Harpending, they owe to the fact that they are descended from people who adopted agriculture long before the ancestors of the Thais.

The majority of Thai Chinese are the descendants of immigrants from Guangdong in southern China. Most of the others came from Hakka and Hainan, also in the south. Rice and millet farming did not reach southern China until about 4,000 BCE[17] and reached northern Thailand no more than 1,000 years later,[18] probably brought by immigrants from China who are the main ancestors of the ethnic Thais.[19]

In other words, ethnic Thais are probably descended from people who have been exposed to agriculture as long as the ancestors of the Thai Chinese. This makes it difficult to see how Cochran and Harpending’s thesis could explain their economic success.

Surely they owe their success to the simple fact that they are a diaspora and an ethnic minority. Members of a diaspora tend to stumble into an economic niche. The first arrivals make their living in a certain way and set up networks of patronage that encourage more arrivals and give them a profitable niche to slot into once they reach their new home.[20] The exact niche migrants slot into can often be quite random: Sikhs drive taxis in many parts of the world but sell cloth in Thailand; Turks sell kebabs in Britain and ice cream in Taiwan; Thais open restaurants in Britain and massage parlours in Germany; and in my home town in south-east England, people from Madeira have something of a stranglehold on cleaning jobs in the local hospital.

Cochran and Harpending claim that restraint is one of the bourgeois virtues bred into our ancestors by their exposure to agriculture, because farmers need to learn not to eat their seed corn no matter how precarious the food situation. This self-control is contrasted with the fecklessness of Bushmen who sabotage efforts to turn them into herders by eating all their goats.

Do the authors seriously believe that Bushmen are so stupid? Is this really a case of idiotic hunter gatherers? Or is it a case of a top-down innovation imposed on a community that never wanted it? It is a basic tenet of management theory that innovations will fail if those who are expected to implement them do not feel some ownership of them.[21] The most likely explanation is that the Bushmen who ate their final goats knew exactly what they were doing – to use the vernacular, they were giving the finger to the man.[22]

In a similar vein, Cochran and Harpending claim that opposition to neo-liberalism in Latin America is fuelled by the fact that the people’s native American ancestors were not exposed to agriculture for as long as the ancestors of Europeans and North Americans and so have fewer genes for bourgeois values. Isn’t it a simpler explanation to say that socialism remains a potent force in Latin America because the industrial working class there is expanding rather than shrinking?

The book argues that genes for aggression have been bred out of populations exposed to agriculture for a long time. One can imagine an experiment in which subjects from two different populations, the one long-term agrarian, the other hunter gatherer, are tested for aggressiveness. This could be done by someone bumping into them on their way to the lab and calling them an asshole. They could then be subjected to various tests, including saliva samples tested for testosterone and cortisol, the hormones that drive aggression and arousal, to see how angry the experience has made them.

In fact, this experiment has already been conducted, in the University of Michigan more than 20 years ago. The results were startling: members of one group tended to brush the incident off with scarcely a second thought while most members of the other group were furious. But both groups were descendents of Europeans long exposed to agriculture and there is no suggestion of any significant genetic difference between them. The difference was cultural: the calmer group were from the north of the USA and the more prickly subjects came from the south, where there is still a culture of honour that leads people to treat perceived insults very seriously indeed.[23]

Cochran and Harpending’s hypothesis that agriculture has altered our personalities may be coherent and logical but the evidence for it is nothing like as clear as they imagine. Their account contains questionable facts and they overestimate the importance of the bourgeois values of hard work and restraint in pre-capitalist society. They also invoke their hypothesis to explain phenomena that are much more easily explained in other ways. They remind me of a certain type of Marxist: their theory explains everything and everything is evidence for their theory.

I believe the technical term is confirmation bias.

THE INTELLIGENCE OF AHKANAZI JEWS

Cochran and Harpending’s third controversial hypothesis is support for the view that Ashkenazi Jews are more intelligent than everyone else. This is a very specific claim that one particular ethnic group has been subjected to evolutionary pressures that have led them to develop IQs that are higher on average than the IQs of both gentiles and other Jewish communities.

As the authors claim, a strong taboo against marrying out means that the Ashkenazim have been a genetically closed community for more than a thousand years. They pay a heavy price for this in their susceptibility to number of serious congenital conditions, among them Tay-Sacks disease, Gaucher’s disease and two types of breast cancer.

But on the other hand, the average IQ of Ashkenazim is 112-115, which compares to 100 for the European population as a whole. Ashkenazi Jews also enjoy an extraordinary intellectual prominence. They have won 25% of Nobel prizes and have provided half of the world’s chess champions. Jews (the great majority of them Ashkenazim) make up just 3% of the USA’s population but 20% of its CEOs and 22% of Ivy League students. Clearly something significant is happening here that needs an explanation.

Cochran and Harpending favour the theory that the high intelligence of Ashkenazi Jews is genetically determined because for several hundred years starting around 1100 CE, the Jews of northern Europe were restricted to white-collar occupations, in particular money lending. This work required above average intelligence and put real selective pressure on them. Those who were more intelligent would be more successful, and the wealth this would bring them gave them greater reproductive success.

IQ is itself a very thorny issue. IQ tests measure different skills, including analytic thinking, mathematical ability, short-term memory and spatial recognition. Proponents of IQ testing argue that these skills are interconnected and that people who are good at one of them tend to be good at the others. Hence the idea of g, a general intelligence that can be measured.

Efforts to propose alternative models of multiple intelligences have tended to founder because of a lack of empirical evidence.[24] There is no doubt that IQ tests have predictive power. As science journalist Michael Balter puts it: ‘Kids who score higher on IQ tests will, on average, go on to do better in conventional measures of success in life: academic achievement, economic success, even greater health, and longevity.’[25]

However, as one investigates the question of IQ, the data presented by Cochran and Harpending begins to look superficial. The first issue is the heritability of IQ. It is generally accepted that IQ is polygenetic with as many as 50 different genes involved.[26] This means that while clever parents tend to have clever children, there is no guarantee. Indeed, if two extremely intelligent people have children, regression to the mean would suggest that their children are likely to be less intelligent than them. Nevertheless, it is reasonable to argue that in a genetically closed population subjected to the pressures Cochran and Harpending describe, the average level of intelligence might be expected to rise.

There is a general consensus that the relative influence of nature and nurture shifts during a person’s life. For children, the heritability of IQ is about 0.45 where 0 = not at all and 1 = completely.[27]       By adolescence, the nature-nurture ratios have been reversed and IQ is 0.75 heritable. In adults, this has risen to 0.85 and we have to a significant degree reached the level of intelligence that our genes determined for us. However, a figure of 0.85 mans our environment still has an impact; there will be some able to punch above their weight and others who never realise their potential.

Because the heritability of IQ shifts so much in the course of our lives, when Cochran and Harpending say that the average IQ of Ashkenazim is 12-15% higher than the rest of us, this statistic tells us nothing about the heritability of Ashkenazi IQs unless we also know the ages of the people being discussed. More information is needed before this claim can be assessed.

Even if the inherited intelligence of Ashkenazi Jews is high, that may not necessarily be the prime cause of their success. They may owe this more to the networks of patronage that they have been able build up in various professions.[28]

Another issue where I feel that Cochran and Harpending have not supplied enough data for their claims to be assessed is the question of just how many Ashkenazi Jews worked as moneylenders during the middle ages. They cite a study of Roussillon circa 1270 which apparently shows that 80% of the Jews there supported themselves by money lending to the virtual exclusion of all other activities.

I find this unconvincing. In 1215 the Fourth Lateran Council legislated against the improper subordination of Christians by Jews. Wouldn’t this make Jews unable to employ Christian servants? If so, there must have been a sizeable class of Jewish servants. Blogger Razie Mah[29] says that a figure of more than 50% engaged in full-time money lending is unlikely since Jews were confined to ghettoes that had separate micro-economies with Jewish teachers, doctors, merchants and food service providers. Even if 80% of Jews lent money, some of them may simply have been topping up an income that was primarily derived from other sources. Many of the amounts lent were tiny and there are indications that most Jewish money lending was in fact pawn brokering.[30] Presumably running a pawn shop takes less brains than running a bank.

Despite these caveats about the quality of the evidence Cochran and Harpending present, I consider their basic hypothesis to be credible. There is no a priori reason why the heritable intelligence of every ethnic group should be the same. The Ashkenazi Jews are a very unusual case, a genetically closed population subject to severe restrictions which may have had the effect of raising their average intelligence.

CONCLUSIONS

It is often said that there should be no no-go areas for scientific research. If science comes up with some uncomfortable truths about race, then we are going to have to live with them. Should it turn out that people of different ethnic groups do, on average, have different levels of intelligence or different personal characteristics, we will have to remember to treat each person as an individual and judge them on their merits, not according to average characteristics of their ethnic group which they may or may not share.

This is fair enough, though I am not optimistic that everyone would remember to do so. Racists will always gleefully seize upon any evidence of the superiority of their group, and otherwise decent people might find that their subconscious attitudes are affected in ways that creep into their behaviour unnoticed. If this led teachers to have lower expectations of certain pupils or made employers less willing to hire or promote on the basis of ethnicity, the life chances of members of stigmatised ethnic groups would suffer greatly.

However, if this book is the best that proponents of such differences can come up with, we do not appear to have reached that stage. The 10,000 Year Explosion makes noteworthy points about physiological differences between the races and asks an interesting question about the intelligence of Ashkenazi Jews without quite supplying the answer. But it has conspicuously failed to demonstrate any other link between race and either intelligence or character. Cochran and Harpending’s hypothesis about Neanderthal DNA and the Upper Palaeolithic revolution is highly speculative and quite possibly redundant, and their claims about bourgeois values and agriculture rest on questionable evidence and a willingness to ignore simpler and more obvious explanations.

NOTES

All websites cited were accessed in July 2015.

[1] http://www.amren.com/ar/2009/05/index.html#article1

[2] For a discussion of this issue, see Bar-Yosef, Ofer 2002. The Upper Paleolithic Revolution in Annual Review of Anthropology Vol. 31, pp. 363-393

[3] http://www.ancient-origins.net/news-evolution-human-origins/discovery-70000-year-old-african-settlement-challenges-previous

[4] http://www.nature.com/scitable/knowledge/library/the-transition-to-modern-behavior-86614339

[5] http://io9.com/5930463/modern-culture-emerged-in-africa-20000-years-earlier-than-anybody-realized
[6] Hovers, Erella and Kuhn, Steven, Eds. 2006. Transitions Before the Transition: Evolution and Stability in the Middle Paleolithic and Middle Stone Age (Interdisciplinary Contributions to Archaeology), Springer.
[7] http://www.china.org.cn/english/China/219830.htm

[8] http://jad.sagepub.com/content/9/2/413

[9] Allsworth-Jones, Phillip 2010. West African Archaeology: New Developments, New Perspectives, British Archaeological Reports International Series.

[10] Gammage, Bill 2013. The Biggest Estate on Earth: How Aborigines Made Australia, Allen & Unwin. See also http://www.australasianscience.com.au/article/issue-july-august-2010/evidence-indigenous-australian-agriculture.html and http://www.abc.net.au/radionational/programs/bushtelegraph/rethinking-indigenous-australias-agricultural-past/5452454

[11] Harari, Yuval Noah 2013. Sapiens: A Brief History of Humankind, Harvill Secker, Chapter 16.

[12] Landes, David 1999. The Wealth and Poverty of Nations. Abacus, p 32.

[13] Le Roy Ladurie, Emmanuel 1980. Montaillou: Cathars and Catholics in a French Village 1294-1324. Penguin Books, p 339.

[14] Tawney, R.H. 1938 Religion and the Rise of Capitalism Pelican Books, pp 44, 48

[15] Tawney op cit pp 230, 239.

[16] Tawney op cit pp 96, 208.

[17] http://www.krazykioti.com/articles/chickens-and-millet-early-agriculture-in-china/

[18] Glover, Ian 2004. Southeast Asia: From Prehistory to History, Psychology Press p 29.

[19] Kongrut, Anchalee, Bones Tell Story of Thai Origin, Bangkok Post 5 November 2006.

[20] http://www.sscnet.ucla.edu/soc/faculty/waldinger/pdf/B13.pdf

[21] See Johnson, Spencer 1999 Who Moved My Cheese, Ebury Publishing for an entertaining exposition of this point.

[22] Harari op cit Chapter 3 suggests that hunter gatherers may in fact be more intelligent and adaptive than those who have been exposed to agriculture for a long time.

[23] See Gladwell, Malcolm 2009 Outliers: The Story of Success, Penguin Books pp 170-174, but see also https://www.psychologytoday.com/blog/the-human-beast/200904/is-southern-violence-due-culture-honor .

[24] Geake, John 2008 Neuromythologies in education, Educational Research 50 (2), pp122-33.

[25] http://news.sciencemag.org/2011/04/what-does-iq-really-measure

[26] http://whatisgenetic.com/2015/05/18/how-to-genetically-engineer-your-children-to-be-rich/

[27] Neisser, Ulrich et al Intelligence: Knowns and Unknowns, American Psychologist 51 (2): pp 77-101.

[28] Gladwell op cit Chapter 5 offers a purely social explanation of Jewish success in the American legal profession.

[29] http://history.stackexchange.com/questions/8032/what-percentage-of-jews-were-in-finance-money-lenders-throughout-middle-ages

[30] Chazan, Robert 2010, Reassessing Jewish Life in Medieval Europe, Cambridge University Press, p 125.