Saturday, August 16, 2014

Book Review: A Troublesome Inheritance

This book about race and the human genome (by former NYTimes reporter Nicholas Wade) will neither shock nor surprise the reader already schooled in evolutionary psychology. I, for example, have read much of the antecedent literature, and little of the data was totally new to me (though I still learned a lot). The book is well-written and well-documented. The author is careful not to overstate his case, even while speculating beyond the hard facts.

The principle thesis of the book is that race (and more broadly, ethnicity) is more than skin deep. The book demonstrates--conclusively in my view--that there are genes that influence behavior, and that these are unevenly distributed among racial groups. One example that he describes in detail is the MAO-A promoter sequence, a variable piece of DNA that regulates aggressive behavior.

The book is very careful not to make too much of this. It's not as though there are "Caucasian genes" and "Asian genes." We are all one species, and the races have been separated for at most 50,000 years. At most the races constitute sub-species--such as dog breeds--but Mr. Wade won't even go that far. Instead, the phenomena is much more subtle, and not necessarily observable at the level of an individual.

Genes mutate through natural processes such as cosmic radiation, transcription errors, and whatnot. Most of these mutations are harmless, most of the rest are harmful or even fatal, but a few of them confer some benefit on the individual and his/her offspring. These latter will be propagated throughout the population.

When mutations are very beneficial, they sweep the entire population until 100% of all individuals possess those genes--we say they have reached fixation. Most genes that we have inherited from our mammalian ancestors, along with many human genes, have reached fixation and are common to all human beings. Those genes are what make us human.

But some genes are not so obviously beneficial--they confer benefits only under some circumstances. For example, the gene for sickle cell anemia is beneficial to those who live in malarial climates, but counterproductive everyplace else. It is thus most commonly found among West Africans. These genes do not sweep the entire population, but instead coexist with other variants of the same gene. These coexisting gene mutations are known as alleles.

So it would be easy to claim that White people have one set of alleles, while Asians another set. But that is also an oversimplification. Consider two alleles of a given gene--label them A and B. In Caucasians, allele A might be found in 75% of the population, while in Asians it may only be found in 40% of the population. Thus it's not that each race has a separate set of alleles, but the frequency of alleles varies between the races. By looking at the allele ratio for multiple genes (typically in the dozens) it is possible to determine the race of the individual to within 90% accuracy (i.e., an answer that corresponds to how the person assigns his own race).

So there is no question that race is inscribed in our genes. The second claim is that there are genes for behavior. This seems obviously true--certainly animal behavior is regulated by genes, and it would be strange if that weren't also true for humans in some degree. The elucidation of the function of the MAO-A promoters (among other genes) demonstrates this conclusively.

There are certain complex behaviors that determine social interactions. For example, how big is the circle of trust? A small circle consisting only of kin will predominate in tribal societies. A much bigger circle is necessary for urban individuals who participate in a global economy. However, there is not a gene for "trust." Instead, trust is regulated by a large number of genes, and can be modified by slight changes the frequencies of various alleles. These frequencies probably do not change by much--most people are fairly trusting--and we have neither identified any of the relevant genes, nor successfully measured the frequencies of the alleles. Still, it is a very reasonable hypothesis that evolution can modulate social interactions to optimize the individual's chances in their current environment. Jews, for example, have long lived in urban environments that put a premium on trust--that's why they're successful bankers. Australian aborigines, on the other hand, lived as tribal hunter-gatherers for 46,000 years, up until the arrival of Europeans in the 17th Century--their ability to function as global citizens will be much more limited.

The third thesis is that evolution happens fast. My Trotskyist friends, for example, have long argued that evolution takes "millions of years," and that within the timeframe of human history our biology was static. But with the advent of modern genomics, we know that evolution operates on much faster timescales. It is now possible to measure human evolution to within the last 3,000 years, and that limit is simply an experimental restriction. With better data (that we shall soon accumulate), there is every reason to think that measurable evolution can occur within a few centuries. This is especially true if the environmental driver is very strong, e.g., birth control.

So the claim of Mr. Wade's book is that people evolve to optimize their success in their environment. If that environment is cultural, then cultural traits will soon be inscribed in the genome. China, for example has existed as a unified nation under autocratic rule since 221 BC. That they will suddenly turn into a Western-style democracy just because a few McDonald's restaurants have opened up is surely a silly thesis. Behavioral traits such as conformity, obedience, thrift, hard work, and a large trust circle are likely not merely cultural phenomena anymore--they are part of the genetic heritage. Mr. Wade's book predicts that someday soon we will be able to prove that through an analysis of the human genome. I think he's right.

By demographic measures, the Han Chinese are the most successful people on earth. They are clearly optimized for their environment.

I'll add three comments of my own. First, people like my Trotskyist friends who claim that evolution stopped the minute human beings came along can no longer justify that belief on facts. Theirs is no longer a scientific opinion. Our ability to analyze the genome directly completely discredits that point of view.

Second, the public policy implications of this data are pretty small. It implies that efforts to change people's personality, either through education or economic motivation, will probably fail. Personality is substantially heritable, and the part that isn't heritable is not easily addressed institutionally. Schools can educate students, but they can't build character or instill good citizenship. Those traits depend on culture and genes, neither of which are amenable to schooling. Head Start failed, not because it was bad educational practice, but because it wanted to give its students a personality transplant. That goal was impossible.

Finally, moral claims are unchanged. To put it in religious terms, God Loves You. It doesn't matter what your alleles are--we are all created in the image of God. Or, in more secular language: We hold these truths to be self-evident...

Further Reading:

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