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Evolution and Human History, Part II

Front Cover

As I said in yesterday's entry, Wade argues that the human race has continued to evolve subsequent to its spread across the eastern hemisphere. When it had spread, it was in effect divided into three habitats: Africa, east Asia, and 'the rest,' that is, all Eurasia west of the Himalayas. The geographical barriers were great enough to make further evolutionary (genetic) change a matter of divergence.

From this situation arose distinctions among races/subspecies that are not "social constructs," but genetic facts.

As the result of a period of climate change and melting ice caps, rising sea levels cut Australia off from East Asia, though allowing for a lot of "stepping stones" between. This allowed for the divergent development of the Aborigine people of Australia.

Later, around 15,000 years ago, the northernmost east Asians, Siberians, crossed into the Americas. Some genetic divergence has arisen subsequent to that crossing, too.  Thus, by the time of the species' earliest written records, there were five distinct continental races, along with various admixed populations and subgroups.

I'm not an expert in any of the fields of science involved. Wade, like myself a journalist by trade, isn't an expert either. But I have to say I find it all plausible. In terms of the old nature/nurture dichotomy, I'm inclined to see both nature and nurture as real facts contributing to the reality of human life. Further (so long as we don't introduce value judgments at this point), I believe we can say inoffensively that the nature part of our selves, the genetic part, is not necessarily identical, and that differences go beyond the most obvious ones of pigmentation, hair follicles, etc. The example I mentioned yesterday of the Tibetan adaptation to high altitudes is an example. No amount of training will turn me into a suitable denizen of the Himalayas, or could have done so even had the training begun at my birth.

Another subtler example is the anatomy behind the human ability to read facial expressions. This has a lot to do with a species anatomical peculiarity, the whites of our eyes, called the "sclera,"  which serves as the backdrop where our iris' move around. We can see each others' iris move around in the sclera. So we say "I'm following your eyes" or "stop rolling your eyes at me." To some uncertain extent, our human sociability derives from ... the whites of our eyes.

Wade discusses the sclera briefly and then drops it. But it will serve as another example. Different gene lines have different ocular anatomical features., including (perhaps) the iris-to-sclera ratio. That might underlie the experience in which people of one race have difficulty reading the expressions of people of another. Inscrutability, if you will.

Where the discussion gets a good deal more speculative (even as "troublesome" as the title of the book suggests)  is that Wade wants to persuade is that people come to inherit patterns of behavior. The ability to breathe thin air isn't a behavior, it's a capacity. Likewise,  the iris-to-sclera ratio isn't a behavior. But Wade's broad thesis includes the proposition that "important aspects of human behavior are shaped by the genes and that these behavior traits are likely to vary from one race to another, sometimes significantly so."

And here I don't believe he has made his case.  Indeed, that's an understatement. The behavior traits he has in mind involve, for example, an individual's willingness (without eagerness) to accept hierarchical authority. We can think of mere "willingness" here as the middle of a continuum, with rebellion against authority on one side and eagerness to accept authority on the other. Wade is in favor of mere willingness here, and he thinks its a racial trait.

The too-happy-with-authority Chinese, he says, allow rulers who are not accountable to law, and this trait leaves the state "defenseless against a bad emperor, of whom the most recent was Mao Tse-tung."

In such passages Wade seems to have gone sliding off the good-science-reporter's greased rails.

One issue often treated in the midst of nature/nurture polemics, on both sides, is the matter of IQ. Some writers regard intelligence, as quantified by testing, as the chief manner in which genes presumably impact behavior. That is not Wade's opinion. Indeed, he spends very little time on intelligence. I'll come back to this aspect of the book next week.


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