A Troublesome Inheritance: Genes, Race and Human History (17 page)

Work hours steadily increased throughout the period, and interest rates fell. When inflation and risk are subtracted, an interest rate reflects the compensation that a person will demand to postpone immediate gratification by postponing consumption of a good from now until a future date. Economists call this attitude time preference, and psychologists call it delayed gratification. Children, who are generally not so good at delaying gratification, are said to have a high time preference. In his celebrated marshmallow test, the psychologist Walter Mischel tested young children as to their preference for receiving one marshmallow now or two in fifteen minutes. This simple decision turned out to have far-reaching consequences: those able to hold out for the larger reward had higher SAT scores and social
competence in later life. Children have a very high time preference which falls as they grow older and develop more self-control. American six-year-olds, for instance, have a time preference of about 3% per day, or 150% per month; this is the extra reward they must be offered to delay instant gratification. Time preferences are also high among hunter-gatherers.

Interest rates, which reflect a society’s time preferences, have been very high—about 10%—from the earliest historical times and for all societies before 1400
AD
for which there is data. Interest rates then entered a period of steady decline, reaching about 3% by 1850. Because inflation and other pressures on interest rates were largely absent, Clark argues, the falling interest rates indicate that people were becoming less impulsive, more patient and more willing to save.

These behavioral changes in the English population between 1200 and 1800 were of pivotal economic importance. They gradually transformed a violent and undisciplined peasant population into an efficient and productive workforce. Turning up punctually for work every day and enduring eight hours or more of repetitive labor is far from being a natural human behavior. Hunter-gatherers do not willingly embrace such occupations, but agrarian societies from their beginning demanded the discipline to labor in the fields and to plant and harvest at the correct times. Disciplined behaviors were probably gradually evolving within the agrarian English population for many centuries before 1200, the point at which they can be documented.

Growth in productive efficiency makes all the difference to economic output, on which a population’s prosperity and survival depend. In 1760, just as the Industrial Revolution was about to take off, 18 hours of labor were required to transform a pound of cotton into cloth. A century later, only 1.5 hours were needed.
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Better technology played a large role in the growth in efficiency. The difference was made not so much by the major inventions beloved of historians, like Richard Arkwright’s water frame or James
Hargreaves’s spinning jenny, but by a continuous stream of incremental improvements as workers drew from and improved upon an expanding pool of common technical knowledge.

Clark has uncovered the simple genetic mechanism through which the Malthusian economy wrought these changes on the English population: the rich had more surviving children than did the poor. From a study of wills made between 1585 and 1638, he finds that will makers with £9 or less to leave their heirs had, on average, just under two children. The number of heirs rose steadily with assets, such that men with more than £1,000 in their gift, who formed the wealthiest asset class, left just over four children.

Figure 7.5. Surviving children by assets of the testator.

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The English population was fairly stable in size from 1200 to 1760. In this context, the fact that the rich were having more children
than the poor led to the interesting phenomenon of unremitting social descent. Most children of the rich had to sink in the social scale, given that there were too many of them to remain in the upper class.

Their social descent had the far-reaching genetic consequence that they carried with them inheritance for the same behaviors that had made their parents rich. The values of the upper middle class—nonviolence, literacy, thrift and patience—were thus infused into lower economic classes and throughout society. Generation after generation, they gradually became the values of the society as a whole. This explains the steady decrease in violence and increase in literacy that Clark has documented for the English population. Moreover, the behaviors emerged gradually over several centuries, a time course more typical of an evolutionary change than a cultural change.

That a profound change in human social behavior should evolve in just a few centuries may seem surprising, but it is perfectly possible in light of the experiments conducted by Dmitriy Belyaev on domestication (his experiments on breeding both tamer and fiercer rats were mentioned in chapter 3). Belyaev was a Soviet scientist who believed in evolution despite the anti-genetic views of Trofim Lysenko, which were then official doctrine in the Soviet Union. In a remote institute in Novosibirsk, he began to test his theory that ancient farmers had domesticated wild animals by a single criterion, that of tameness. All the many other traits that distinguish domestic animals from their wild forebears—thinner skulls, patches of white hair, floppy ears—had been dragged along in the wake of the selection for tameness, Belyaev supposed.

He began by selecting silver foxes for tameness, taking the remarkable gamble that he would see within his lifetime a change that may have taken ancient farmers many hundreds of years to accomplish. Yet within eight generations, Belyaev had bred silver foxes that would tolerate human presence. Just 40 years after the experiment
had started and with 30 to 35 generations of breeding, the foxes were as tame and biddable as a dog. And just as Belyaev had predicted, the tamer foxes had white patches on their coats and droopy ears, even though these traits had not been selected for.
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Belyaev’s work, which did not become known outside the Soviet Union until 1999, demonstrated how quickly a profound evolutionary change in behavior could occur. Assuming 25 years per generation, there would have been 24 human generations between 1200 and 1800, plenty of time for a significant change in social behavior if the pressure of natural selection were sufficiently intense.

In a broader sense, these changes in behavior were just some of many that occurred as the English population adapted to a market economy. Markets required prices and symbols and rewarded literacy, numeracy and those who could think in symbolic ways. “The characteristics of the population were changing through Darwinian selection,” Clark writes. “England found itself in the vanguard because of its long, peaceful history stretching back to at least 1200 and probably long before. Middle-class culture spread throughout the society through biological mechanisms.”
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Economic historians tend to see the Industrial Revolution as a relatively sudden event and their task as being to uncover the historical conditions that precipitated this immense transformation of economic life. But profound events are likely to have profound causes. The Industrial Revolution was caused not by events of the previous century but by changes in human economic behavior that had been slowly evolving in agrarian societies for the previous 10,000 years.

This, of course, explains why the practices of the Industrial Revolution were adopted so easily by other European countries, the United States and East Asia, all of whose populations had been living in agrarian economies and evolving for thousands of years under the same harsh constraints of the Malthusian regime. No single resource or
institutional change—the usual suspects in most theories of the Industrial Revolution—is likely to have become effective in all these countries around 1760, and indeed none did.

That leaves the questions of why the Industrial Revolution was perceived as sudden and why it emerged first in England instead of in any of the many other countries where conditions were ripe. Clark’s answer to both these questions lies in the sudden growth spurt in the English population, which tripled between 1770 and 1860. It was this alarming spurt that led Malthus to write his foreboding essay on population.

But contrary to Malthus’s gloomy prediction of a population crash induced by vice and famine, which would have been true at any earlier stage of history, incomes on this occasion rose, heralding the first escape of an economy from the Malthusian trap. Incomes grew because the production efficiency of the English economy had been steadily increasing since 1600. It had reached such a level that, combined with the sudden rise in population, the output of the English economy became visibly larger. English workmen contributed to this spurt, Clark drily notes, as much by their labors in the bedroom as on the factory floor.

The rise in population that made England’s exit from the Malthusian trap so visible was an unrelated event, in Clark’s view. It had no part in causing the escape but merely amplified a process that was already under way. Clark attributes it to women’s perception that the once substantial risks of death in childbirth had dropped substantially since the 17th century. In 1650 a woman who had the average number of children had a 10% chance of dying in childbirth. This formidable risk had dropped to just over 4% by the early 19th century. In 1650, 20% of women never married, and the perceived risk of doing so would have been a rational deterrent. By the early 18th century the proportion of spinsters had fallen to 10%. This and the
trend to younger marriages propelled a 40% increase in English fertility between 1650 and 1800.
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Clark’s thesis departs considerably from the mainstream views of economic historians and political economists, most of whom look to institutions to explain major issues such as world poverty and the Industrial Revolution, even though each has a different favorite, whether intellectual property rights, the rule of law or parliamentary democracy. Clark dismisses this whole category of explanations as insufficient. Many early societies, he says, had all the preconditions for economic growth that any World Bank economist could wish for, yet none did so. “Economic historians,” Clark writes, “thus inhabit a strange netherworld. Their days are devoted to proving a vision of progress that all serious empirical studies in the field contradict.” They are thus “trapped in this ever-tightening intellectual death spiral.”

Clark’s book was widely noticed and, unsurprisingly given its heterodoxy, many reviews were critical. Some reviewers dismissed Clark’s thesis as peremptorily as he had dismissed theirs. Several disagreed with his assertion that England prior to the Industrial Revolution was under a true Malthusian regime, an issue of contention among economic historians. Others disputed Clark’s calculation about human wealth before agriculture, which has to be inferred from that of living hunter-gatherers. However the strictly economic issues may be resolved, there were relatively few attacks on Clark’s proposed mechanism of evolutionary change, the ability of the rich to leave more surviving children who would spread their genes and behavior through the population as some of them descended in social rank.

Clark has since corroborated this mechanism by devising an independent way to check it, based on the prevalence of surnames. Surnames, being passed from father to son, are effectively propagated like the Y chromosome. They track male genes, provided that wives
are faithful and no one is adopted, but cases of nonpaternity and adoption were both rare in medieval England. Clark chose two sets of rare surnames, such as Banbricke, Cheveney, Reddyforde, Spatchet and Tokelove, from English records of 1560–1640. One set belonged to men rich enough to leave a will, the other to people indicted in Essex courts for burglary, poaching and crimes of violence, and therefore assumed to be among the poorest.

For rare surnames, a large fraction of the holders will typically be related. Clark found that his rich families survived through the generations much better than the poor ones. By 1851 only 8% of the richest surnames from the 1560–1640 period had disappeared, but 21% of the indicted surnames no longer existed. The poor have a greater risk of being erased from the gene pool.

But it is not the case, Clark found, that a permanent rich elite survives in perpetuity. Rather, there has been considerable social mobility in English society. Many of the rare surnames that belonged to rich families in 1560–1640 belonged to people in middle- or lower-income occupations, and some of the indicted surnames from the earlier period had risen into the gentry by 1851.

“The surname evidence confirms a permanent selection in pre-industrial England for the genes of the economically successful, and against the genes of the poor and the criminal,” Clark concludes. “Their extra reproductive success had a permanent impact on the genetic composition of the later population.”
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Clark’s data provide substantial evidence that the English population responded genetically to the harsh stresses of a Malthusian regime and that the shifts in its social behavior from 1200 to 1800 were shaped by natural selection. The burden of proof is surely shifted to those who might wish to assert that the English population was miraculously exempt from the very forces of natural selection whose existence it had suggested to Darwin.