Friday, June 22, 2012

Book Review: Born Together—Reared Apart -

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Some findings go down easy: As most would expect, identical twins raised apart have virtually identical heights as adults. Some findings seem obvious after the fact: Genes, but not upbringing, have a pretty big effect on personality traits like ambition, optimism, aggression and traditionalism. Other findings perennially cause outrage: The IQs of separated identical twins are almost as similar as their heights. Critics of intelligence research often hail the importance of practice rather than inborn talent, but a three-day test of the Minnesota twins' motor skills showed that how much you benefit from practice is itself partly an inborn talent.

The Minnesota study's IQ results hit a nerve years before their publication in 1990, overshadowing other controversies that might have been. Many of its findings are bipartisan shockers. Take religion, which almost everyone attributes to "socialization." Separated-twin data show that religiosity has a strong genetic component, especially in the long run: "Parents had less influence than they thought over their children's religious activities and interests as they approached adolescence and adulthood." The key caveat: While genes have a big effect on how religious you are, upbringing has a big effect on the brand of religion you accept. Identical separated sisters Debbie and Sharon "both liked the rituals and formality of religious services and holidays," even though Debbie was a Jew and Sharon was a Christian.
"Born Together—Reared Apart" is an excellent book for a serious, statistically literate reader who already knows the basics of twin research. But livelier, more accessible introductions are already on the market—most obviously Ms. Segal's earlier "Entwined Lives" (1999). "Born Together—Reared Apart" is, however, a joy to read when she describes the awe of reuniting twins—and the joy of seeing many become soul mates before her eyes. And despite her focus on academic research, Ms. Segal shares some of her casual observations, such as that one pair of identical twins both held their beer glasses with a pinkie hooked underneath.

Ms. Segal has little patience for those who fear the social consequences of the Minnesota Study. The facts are on her side. Scientific support for the effect of heredity on ability, character, and success has been mounting for decades, but Western societies are more tolerant than ever, and more inclined to treat their members as individuals. Hatemongers have no need to appeal to heredity. Nazis used genetics to rationalize genocide. Communist regimes rejected genetics as "bourgeois" and murdered millions for their counterrevolutionary family backgrounds. When a powerful movement wants to commit a heinous crime, it makes up a reason. The wise response isn't to argue the science but to insist that we should treat others with common decency, no matter what the science says.

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