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BOOK REVIEW

A Troubling Tome

Greg Laden

There is a more straightforward explanation for behavioral variation among humans, much more likely accurate than the one Wade proposes. This explanation is embedded in current anthropological thinking and fits better with observations of what makes humans unique among kindred species.

It ties back to individual human development. Our species pays a huge evolutionary cost for its extended childhood. Unlike our ape relatives, we are born and remain for years nearly helpless and at risk. Birth itself is costly and dangerous because of our large brain. These things are linked. A typical human adult is imbued with human qualities by virtue of an extended period of learning and enculturation during which that big brain is shaped by its environment. Were our children born with more genetic programming for social behavior, the brain could potentially be smaller, growing up could be faster, the emergence of appropriate behavior more reliable, and reproductive output higher.

Our large brains have a high metabolic cost as well, and accounting for this cost has been central to many recent theories of human evolution, including Richard Wrangham and his colleagues’ cooking hypothesis and Leslie Aiello and Peter Wheeler’s expensive-tissue hypothesis, which together explain where the energy for growing and maintaining large brains comes from.

Our relatively slow reproductive rate and the extended demands of child rearing are thought to be compensated for by the evolution of reproductive senescence (menopause). “The Grandmother Hypothesis,” as it’s sometimes called, posits that older women forgo their own reproduction in favor of providing critical investment in raising grandchildren. These contemporary interpretations of human evolution do not exclude genetic change; large brains, language, menopause, and other unique human features clearly have genetic underpinnings. But the features themselves seem linked to a system of developing appropriate social behavior as part of human cultural adaptability and are not expected to manifest as distinct fine-tuned genetic adaptations in different races.

Most likely, a key human trait involved is an adaptability to diverse contexts through learning, which is in turn facilitated by these costly features. Hence, an excellent explanation for variation across human populations is culture, not genes.

Learning and enculturation explain most human behavioral variation. This is a basic tenet of modern anthropology. Perhaps the best evidence is the simple fact that children adopted as infants across vast cultural boundaries do not carry their parents’ social behavior with them. More broadly, sudden large-scale changes in national or regional economy, such as the uniting of East and West in Germany, produce rapid change in IQ measures and social behavior. Oddly, Wade acknowledges that these things happen within a race, or at least one race (Caucasian), but insists that when the same traits vary across races they can be accounted for only by evolutionary genetic change.

Ultimately, Wade claims that modern anthropology ignores key scientific information for political reasons, yet his own arguments are only thinly supported by data, and much of the data he does reference isn’t rigorous. To his credit, he refutes certain racist notions associated with the idea of genetic determinism, and he speaks against social Darwinism and similar concepts. But if that verbiage were excised, his book would fit comfortably in the early to mid-20th century literature on race and human variation. A Troublesome Inheritance is itself troubling, not for its politics but for its science. Its arguments are only mildly amended versions of arguments discarded decades ago by those who methodically and systematically study human behavioral variation across cultures.

Greg Laden is a biological anthropologist who has worked in the Democratic Republic of Congo and South Africa. He writes at Scienceblogs.com.




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