Book Summary: “A Troublesome Inheritance: Genes, Race and Human History” by Nicholas Wade


Title: A Troublesome Inheritance: Genes, Race and Human History
Author: Nicholas Wade
Scope: 4 stars
Readability: 3.5 stars
My personal rating: 5 stars
See more on my book rating system.

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Topic of Book

Wade explores the controversial topic of genetics, race and their impact on human history.

My Comments

The current faddish belief that race is a social construct is overwhelmingly contradicted by genetic evidence. So is the theory that there are no genetic differences between races. This belief is a failed attempt to impose ideology on science.

Key Take-aways

  • Race is a biological category.
  • Racial differences are not based upon individual genes. They are based upon slight differences in frequency of alleles.
  • Using 326 AIMs, or ancestry informative markers, researchers achieved a nearly perfect correspondence between the race that subjects said they belonged to and the race to which they were assigned genetically.
  • Over the past 30,000 years human genetic evolution has accelerated and caused regional differences between human populations.
  • About 14% regions of the human genome has been under recent evolution. And those regions differ by race.
  • Historians, social scientists and economists mistakenly assume that all people are genetically identical, so they have not examined the possibility that difference between societies might be partly rooted in biology.
  • The brisk and continuing pace of human evolution suggests a new possibility: that at the root of each civilization is a particular set of evolved social behaviors that sustains it, and these behaviors are reflected in the society’s institutions. Institutions are not just sets of arbitrary rules. Rather, they grow out of instinctual social behaviors, such as the propensity to trust others, to follow rules and punish those who don’t, to engage in reciprocity and trade, or to take up arms against neighboring groups.To say that genes explain everything about human social behavior would be as absurd as to assume that they explain nothing.
  • Social institutions are a blend of genetics and culture. Each major institution is based on genetically influenced behaviors, the expression of which is shaped by culture.
  • Until 1900, the wealthy had more surviving children than the poor. This enabled heritable traits that promoted success in a society to gradually expand.

Important Quotes from Book

Since the decoding of the human genome in 2003, a sharp new light has been shed on human evolution, raising many interesting but awkward questions.

It is now beyond doubt that human evolution is a continuous process that has proceeded vigorously within the past 30,000 years and almost certainly—though very recent evolution is hard to measure— throughout the historical period and up until the present day.

Because of these divisions in the human population, anyone interested in recent human evolution is almost inevitably studying human races, whether they wish to or not. Scientific inquiry thus runs into potential conflict with the public policy interest of not generating possibly invidious comparisons that might foment racism. Several of the intellectual barriers erected many years ago to combat racism now stand in the way of studying the recent evolutionary past. These include the assumption that there has been no recent human evolution and the assertion that races do not exist.

New analyses of the human genome establish that human evolution has been recent, copious and regional.

No less than 14% of the human genome, according to one estimate, has changed under this recent evolutionary pressure.1 Most of these signals of natural selection date from 30,000 to 5,000 years ago, just an eyeblink in evolution’s 3 billion year timescale.

One of the most recent known dates at which a human gene has been changed by evolution is from 3,000 years ago, when Tibetans evolved a genetic variant that lets them live at high altitude.

“Our study supports the idea that humans are still evolving,” they write. “It also demonstrates that microevolution is detectable over just a few generations in a long-lived species.”

Human evolution has not only been recent and extensive; it has also been regional. The period of 30,000 to 5,000 years ago, from which signals of recent natural selection can be detected, occurred after the splitting of the three major races, and so represents selection that has occurred largely independently within each race.

Analysis of genomes from around the world establishes that there is indeed a biological reality to race, despite the official statements to the contrary of leading social science organizations.

It has long been convenient for social scientists to assume that human evolution ground to a halt in the distant past, perhaps when people first learned to put a roof over their heads and to protect themselves from the hostile forces of nature. Evolutionary psychologists teach that the human mind is adapted to the conditions that prevailed at the end of the last age, some 10,000 years ago. Historians, economists, anthropologists and sociologists assume there has been no change in innate human behavior during the historical period.

The social scientists’ official view of race is designed to support the political view that genetics cannot possibly be the reason why human societies differ— the answer must lie exclusively in differing human cultures and the environment that produced them.

The recent discoveries that human evolution has been recent, copious and regional severely undercut the social scientists’ official view of the world because they establish that genetics may have played a possibly substantial role alongside culture in shaping the differences between human populations.

Another kind of flaw occurs when universities allow a whole field of scholars to drift politically to the left or to the right. Either direction is equally injurious to the truth, but at present most university departments lean strongly to the left. Self-censorship is the frequent response, especially in anything to do with the recent differential evolution of the human population. It takes only a few vigilantes to cow the whole campus.

Racism and discrimination are wrong as a matter of principle, not of science. Science is about what is, not what ought to be. Its shifting sands do not support values, so it is foolish to place them there.

The notion that any race has the right to dominate others or is superior in any absolute sense can be firmly rejected as a matter of principle and, being rooted in principle, is unassailable by science. Nonetheless, races being different, it is inevitable that science will establish relative advantages in some traits. Because of genetic variants, Tibetans and Andean highlanders are better than others at living at high altitudes. At every Olympic games since 1980, every finalist in the men’s 100-meter race has had West African ancestry. It would be no surprise if some genetic factor were found to contribute to such athleticism.

To discover that genetics plays some role in the differences between the major human societies does not mean that that role is dominant. Genes do not determine human behavior; they merely predispose people to act in certain ways.

To say that genes explain everything about human social behavior would be as absurd as to assume that they explain nothing.

If fear of racism can be overcome sufficiently for researchers to accept that human evolution has been recent, copious and regional, a number of critical issues in history and economics may be laid open for exploration. Race may be a troublesome inheritance, but better to explore and understand its bearing on human nature and history than to pretend for reasons of political convenience that it has no evolutionary basis.

It s social behavior that is of relevance for understanding pivotal— and otherwise imperfectly explained—events in history and economics. Although the emotional and intellectual differences between the world’s peoples as individuals are slight enough, even a small shift in social behavior can generate a very different kind of society.

Until the great demographic transition that followed industrialization, the wealthy had more surviving children than the poor. As many of the children of the rich fell in status, they would have spread throughout the population the genes that support the behaviors useful in accumulating wealth. This ratchet of wealth provides a general mechanism for making a specific set of behaviors—those required for economic success—more general and, generation after generation, gradually changing a society’s nature. The mechanism has so far been documented only for a population for which unusually precise records exist, that of England from 1200 to 1800.

One factor almost always assumed to be constant is human nature. Yet if human social nature, and therefore the nature of human societies, has changed in the recent past, a new variable is available to help explain major turning points in history.

Economists and historians attribute the major disparities between countries to factors such as resources or geography or cultural differences… But in situations where culture and political institutions can flow freely across borders, long enduring disparities are harder to explain. The brisk and continuing pace of human evolution suggests a new possibility: that at the root of each civilization is a particular set of evolved social behaviors that sustains it, and these behaviors are reflected in the society’s institutions. Institutions are not just sets of arbitrary rules. Rather, they grow out of instinctual social behaviors, such as the propensity to trust others, to follow rules and punish those who don’t, to engage in reciprocity and trade, or to take up arms against neighboring groups. Because these behaviors vary slightly from one society to the next as the result of evolutionary pressures, so too may the institutions that depend on them.

This would explain why it is so hard to transfer institutions from one society to another.

Human sociality is often assumed to be entirely a matter of culture, originating from the age of life when children are taught to be nice to one another. A cascade of discoveries, many in the past decade, has made clear that this is not the case. Human sociality has been shaped by natural selection, just as might be expected for any feature so crucial to survival.

Nonetheless, it is reasonable to assume that if traits like skin color have evolved in a population, the same may be true of its social behavior, and hence the very different kinds of society seen in the various races and in the world’s great civilizations differ not just because of their received culture—in other words, in what is learned from birth— but also because of variations in the social behavior of their members, carried down in their genes.

The common theme of all these developments is that when circumstances change, when a new resource can be exploited or a new enemy appears on the border, a society will change its institutions in response. Thus it’s easy to see the dynamics of how human social change takes place and why such a variety of human social structures exists. As soon as the mode of subsistence changes, a society will  develop new institutions to exploit its environment more effectively. The individuals whose social behavior is better attuned to such institutions will prosper and leave more children, and the genetic variations that underlie such a behavior will become more common. If the pace of warfare increases, a special set of institutions will emerge so as to increase the society’s military preparedness. These new institutions will feed back into the genome over the course of generations, as those with the social behaviors that are successful in a militaristic society leave more surviving children.

This process of continuous adaptation has taken a different course in each region of the world because each differed in its environment and exploitable resources. As population

Races are a way station on the path through which evolution generates new species.

Races emerge as part of the process of evolutionary change. At the level of the genome, the driving force of evolution is mutation.

Mutation generates novelty in the sequence of DNA units that comprise the hereditary information. The new sequences are then acted on— either eliminated, made more common or ignored—by the evolutionary processes of natural selection, genetic drift and migration.

Those leaving Africa seem to have comprised a few hundred people, consisting perhaps of a single hunter-gatherer band. They took with them only a fraction of the alleles in the ancestral human population, making them less genetically diverse. They spread across the world by a process of population budding. When a group grew too big for the local resources, it would split, with one band staying put and the other moving a few miles down the coast or upriver, a process that further reduced the diversity at each population split.

The evolutionary pressures for change on these small isolated groups would have been intense. Those migrating eastward faced new environments. Living by hunting and gathering, they would have had to relearn how to survive in each new habitat. The groups moving northward from the equatorial zone of the first migration would have encountered particularly harsh pressures.

Each little population started to accumulate its own set of mutations in addition to those inherited from the common ancestral population. And in each population the forces of natural selection and drift worked independently to process these mutations, making some more common and eliminating others.

People as they spread out across the continents at the same time fragmented into small tribal groups. The mixing of genes between these little populations was probably very limited. Even if geography had not been a formidable barrier, the hunter-gatherer groups were territorial and mostly hostile to strangers. Travel was perilous. Warfare was probably incessant, to judge by the behavior of modern hunter-gatherers.

Once the available territory had been occupied, people overwhelmingly lived and died in the region where they were born. The fact that people were pretty much locked within their home territories until modern times is one of the surprises that has come out of the genome.

Using a 500,000 snip chip, researchers at Stanford University have found a strong correspondence between the genetics and geographical origins of Europeans. In fact, 90% of people can be located to within 700 kilometers (435 miles) of where they were born, and 50% to within 310 kilometers (193 miles). Europeans

Why then isn’t the global human population far more varied than it is? Because most of these small tribes were destroyed or absorbed into larger tribes as spread zones, propelled by demographic expansion or conquest, rolled like a wave over vast areas of mosaic zone.

Many of today’s races and ethnic groups were probably once small tribes that expanded through population increase, followed by conquering and absorbing outnumbered peoples.

Those who assert that human races don’t exist like to point to the many, mutually inconsistent classification schemes that have recognized anywhere from 3 to 60 races. But the lack of agreement doesn’t mean that races don’t exist, only that it is a matter of judgment as to how to define them. As with any species that evolves into geographically based races, there is usually continuity between neighboring races because of gene exchange between them. 

One reason that races exist, though not distinctly, is that the features characteristic of a race are often distributed along a gradient.

A practical way of classifying human variation is therefore to recognize five races based on continent of origin. These are the three principal races—Africans, East Asians and Caucasians—and the two other continent-based groups of Native Americans and Australian aborigines (including the people of New Guinea, an island joined to Australia until the end of the last ice age).

Within each continental race are smaller groupings which, to avoid terms like subrace or subpopulation, that might be assumed to imply inferiority, may be called ethnicities. Thus Finns, Icelanders, Jews and other groups with recognizable genetics are ethnicities within the Caucasian race.

One might expect that different races would have different genes, but they don’t. All humans, so far as is known, have the same set of genes. Each gene comes in various alternative forms, called alleles, so the next expectation might be that races would be distinguished by having different alleles of various genes. But this too is not how the system works.

The genetic differences between human races turn out to be based largely in allele frequencies, meaning the percentages of each allele that occur in a given race.

Genetics generally correlates with language family, except in the case of populations that have switched languages.

Pritchard found about 200 genetic regions that showed a characteristic signature of having been under selection (206 in Africans, 185 in East Asians and 188 in Europeans). But in each race, a largely different set of genes was under selection, with only quite minor overlaps.

But if one takes just the regions marked by any two of the scans, then 722 regions, containing some 2,465 genes, have been under recent pressure of natural selection, according to an estimate by Joshua M. Akey of the University of Washington. This amounts to 14% of the genome.

That so much of the genome has been under natural selection strong enough to be detectable shows how intense human evolution must have been in the past few thousand years. A principal driver of evolutionary change would have been the need to adapt to a wide range of new environments. In proof of that point, some 80% of the 722 regions under selection are instances of local adaptation, meaning that they occur in one of the three main races but not in the other two.

Another regional trend indicated by the genome scans is that there seem to be more genes under selection in the genomes of East Asians and Europeans than in those of Africans.

You don’t always need a full sweep to change a trait. Many traits, like skin color or height or intelligence, are controlled by a large number of different genes, each of which has alleles that individually make small contributions to the trait. So if just some of these alleles become a little more common in a population, the trait will be significantly affected. This process is called a soft sweep, to contrast it with a full or hard sweep, in which one allele of a gene displaces all the others in a population.

This soft sweep process—a small increase in frequency in many genes—is a much easier way for natural selection to operate than through the hard sweeps—the major jump in frequency of a single allele—that are often assumed to be the main drivers of evolution. The reason is that the hard sweeps depend on a mutation creating a novel allele of great advantage, which happens only very rarely in a population. In a small population, it may take many generations for such a mutation to occur. Soft sweeps, on the other hand, act on alleles that already exist and simply make some of them more common. Soft sweeps can thus begin whenever they are needed.

In sum, hard sweeps cannot start until the right mutation occurs, and then they may take many generations to sweep through a population. Soft sweeps, based on standing variation in the many genes that control a single trait, can start immediately. For a species that undergoes a sudden expansion in its range and needs to adapt quickly to a succession of different challenges, the soft sweep is likely to be the dominant mechanism of evolutionary change. This explains why so few hard sweeps are visible in the human genome. Soft sweeps are presumably far more common, though at present are very hard to detect.

It is now possible to understand the structure of human variation, at least in broad outline. Different populations don’t have different genes—everyone has the same set. Of the traits specific to one race or another, a few are encoded in hard sweep alleles that have gone almost to fixation, such as the Duffy null allele or some of the alleles involved in shaping skin color, but many more are probably encoded in soft sweeps and hence in mere differences in the frequency of the cluster of alleles that shape each trait.

The fact that genes work in combination explains how there can be so much variation in the human population and yet so few fixed differences between populations.

Medical geneticists have therefore developed sets of test alleles that can be used to distinguish one race from another. Some alleles, particularly those with large differences in frequency between races, are more useful than others. These race-distinguishing DNA sites are known blandly as AIMs, or ancestry informative markers. Using a set of 326 AIMs, researchers achieved a nearly perfect correspondence between the race that subjects said they belonged to and the race to which they were assigned genetically.

Social institutions are a blend of genetics and culture. Each major institution is based on genetically influenced behaviors, the expression of which is shaped by culture. The human instincts for exchange and reciprocity probably undergird much of economic behavior but obviously the expressions of it, from farmers’ markets to synthetic collateralized debt obligations, are cultural.

The genetically based social behaviors that undergird institutions can, like any other hereditary trait, be modulated by natural selection. Human social nature is much the same from one society to another, but slight variations in social behaviors can probably generate significant and long enduring differences in a society’s institutions. A small difference in the radius of trust may underlie much of the difference between tribal and modern societies.

Institutional continuity that extends over many centuries, and over millennia in the case of China, may thus reflect the stability provided by the institutions’ genetic components. One indication of such a genetic effect is that, if institutions were purely cultural, it should be easy to transfer an institution from one society to another. But American institutions do not transplant so easily to tribal societies like Iraq or Afghanistan. Conversely, the institutions of a tribal society would not work in the United States.

Perhaps the most dramatic example of a human society adapting through institutional change is the transition from nomadic hunter gatherer societies to settled groups, which started only 15,000 years ago. The new institutions of settled society required a thorough makeover of human social behavior.

Genetically, hunter-gatherer systems probably gain stability from the fact that variance is suppressed by egalitarianism. Individuals with exceptional qualities, such as great intelligence or hunting skill, cannot take direct advantage of such talents to have more children because of rules that require a catch to be shared with others. The social behavior of hunter-gatherer groups thus had no particularly strong driving force toward change.

The social and genetic variance of the society was greatly increased by these changes. A person with social skills and intelligence had a reasonable chance of getting richer, something that was seldom possible in a hunter-gatherer society, where there were no disparities and no wealth to speak of.

The elites that emerged in the first settled societies were able to raise more surviving children. They developed a keen interest in passing on their advantages of wealth and rank. But if the rich have more children and the population remains the same size, some children of the rich must descend in social rank. The social behaviors of the elites could thus trickle down genetically into the rest of society. The ability of the rich to produce more surviving children created for the first time a powerful mechanism whereby natural selection could enhance successful behaviors. In societies where aggression paid, aggressive men would have more children. In those in which conciliation or trading abilities carried a payoff, people with these traits would leave the larger imprint on the next generation.

A general pattern in world history is that states first developed in regions of high population density.

Throughout much of Africa, the lack of dense populations and large scale warfare, two essential ingredients in the formation of modern states, prevented such structures from arising. Africa south of the Sahara remained largely tribal throughout the historical period, as did Australia, Polynesia and the circumpolar regions.

This, then, is the most significant feature of human races: not that their members differ in physical appearance but that their society’s institutions differ because of slight differences in social behavior.

There is in fact a straightforward explanation for the behaviors of all the migrant groups described by Sowell, in terms of the ratchet of wealth explanation given above for the Industrial Revolution. Populations like Europeans and East Asians, who have adapted, during centuries of living in agrarian systems, to the exigencies of running efficient economies, are at considerable advantage when migrating to other countries. Hard work, efficiency and group cohesion characterize the behavior of East Asian and European migrant groups. It is particularly notable that the Japanese and Chinese should attain higher than average standards of living in the United States, competing against a predominantly European population. The longer history of urbanization in East Asia may underlie part of this competitive advantage.

The argument presented in the pages above is that these differences do not spring from any great disparity between the individual members of the various races. Rather, they stem from the quite minor variations in human social behavior, whether of trust, conformity, aggressiveness or other traits, that have evolved within each race during its geographical and historical experience. These variations have set the framework for social institutions of significantly different character. It is because of their institutions—which are largely cultural edifices resting on a base of genetically shaped social behaviors—that the societies of the West and of East Asia are so different, that tribal societies are so unlike modern states, and that rich countries are rich and poor countries deprived.

The consensus explanation of almost all social scientists is that human societies differ only in their culture, with the implicit premise that evolution has played no role in the differences between populations.

But the all-culture explanation is implausible for several reasons.

First, it is of course a conjecture. No one can at present say what precise mix of genetics and culture underlies the differences between human societies, and the assertion that evolution plays no role is merely a surmise. Second, the all-culture position was formulated largely by the anthropologist Franz Boas as an antiracist position, which may be laudable in motive, but political ideology of any kind has no proper place in science. Moreover Boas wrote at a time before it was known that human evolution had not halted in the distant past.

Third, the all-culture conjecture does not satisfactorily explain why the differences between human societies are as deep-rooted as seems to be the case. If the differences between a tribal society and a modern state were purely cultural, it should be easy to modernize a tribal society by importing Western institutions. American experience in Haiti, Iraq and Afghanistan generally suggests otherwise.

Fourth, the all-culture conjecture is severely lacking in proper care and maintenance. Its adherents have failed to update it to take account of the new discovery that human evolution has been recent, copious and regional. Their hypothesis must assume, against all the evidence that has accumulated over the past 30 years, that the mind is a blank slate, born immaculately bereft of any innate behavior, and that the importance of social behavior for survival is too trivial to have been molded by natural selection. Or, if they allow that social behavior does have a genetic basis, they must explain how it could have remained unchanged in all races, despite the vast changes in human social structure over the past 15,000 years, when many other traits are now known to have evolved independently in each race, transforming some 14% of the human genome.

The thesis presented here assumes, to the contrary, that there is a genetic component to human social behavior; that this component, so critical to human survival, is subject to evolutionary change and has indeed evolved over time; that the evolution in social behavior has necessarily proceeded independently in the five major races and others; and that slight evolutionary differences in social behavior underlie the differences in social institutions prevalent among the major human populations.

Like the all-culture position, this thesis is unproven, but it rests on several premises that are plausible in the light of new knowledge.

The first is that the social structures of primates, humans included, are based on genetically shaped behaviors.

A second premise is that these genetically shaped social behaviors undergird the institutions around which human societies are constructed. Given that such behaviors exist, it seems uncontroversial that institutions should depend on them.

A third premise is that the evolution of social behavior has continued during the past 50,000 years and throughout the historical period. This phase of evolution has necessarily occurred independently and in parallel in the three major races after they split apart and each made the transition from hunting and gathering to settled life. Evidence in the genome that human evolution has been recent, copious and regional provides general support for this thesis, unless any reason can be shown why social behavior should have been exempt from natural selection.

A fifth premise is that the significant differences are those between human societies, not their individual members. Human nature is essentially the same worldwide. But minor variations in social behavior, though barely perceptible, if at all, in an individual, combine to create societies of very different character. A primary effect of genetics is to add a substantial degree of inertia or stability to the social behavior and hence to the institutions of each society. Rapid change must be due to culture, not genetics, but if the core social behaviors of each civilization have an evolutionary foundation, as argued in the previous chapter, then the rate of change in their relationships is likely to be constrained. The slow march of evolution, in other words, exerts an unseen collar on the pace of history.

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