Contemporary Genetics

In the latter half of the twentieth century a field known as behavior genetics came to prominence, focusing largely on animal models (fruit flies, mice, honeybees, spiders). Specific behaviors, such as Drosophila mating dances, were observed to involve several different genetic components, a mutation in any one of which could alter the course and outcome of the mating response. Inevitably attempts were made to apply similar claims to complex human behavior—indeed, to many of the same behaviors that had been the subject of investigation by eugenicists a half century earlier. Starting the late 1960s an up-surge in claims about the genetic basis of traits such as IQ, alcoholism, schizophrenia, manic depression, criminality, violence, shyness, homosexuality, and more newly named traits such as attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD) and "risk taking" became widespread in both clinical and popular literature. Many of these newer studies were carried out by psychologists and psychiatrists employing the more traditional methods of family, twin, or adoption studies, correlated with genetic markers, that is, marker regions of chromosomes or DNA. Many of these studies attracted controversy that threw doubts on much of the methodology on which the current human behavior genetics is based. Among the controversial studies were those published in 1969 by the Berkeley psychologist Arthur Jensen claiming that IQ is 80 percent heritable, based on data collected over a half century by the British psychologist Cyril Burt (later claimed to be spurious or even falsified); a study published in the late 1980s by the Minnesota psychologist Thomas Bouchard of identical twins raised apart, which claimed that traits such as liking John Wayne movies, having wives with the same names, or driving identical cars are genetic in origin (no similar results have been confirmed by other researchers); and a 1994 study by Dean Hamer that claimed to have found a genetic marker associated with homosexuality in thirty-three out of forty pairs of gay brothers but that could not be replicated by a separate lab study using a different study population.

The same methodological problems that confronted eugenicists has confronted many of these current theories: difficulty in defining behaviors in a clear manner; treating complex behaviors as if they were a single entity; the difficulty of separating out familial and cultural inheritance from biological inheritance; the problematic use of statistics, especially "heritability"; and difficulty in replicating the results of one study using a different population. As in the eugenic period, critics of hereditarian studies have argued that despite the uncertainty of the conclusions, the widespread dissemination of the results as positive outcomes serves the social function of distracting attention from social and economic reforms that might go a long way toward altering the prevalence of certain "problem" behaviors. As Thomas Hunt Morgan (1866–1945), the first Nobel laureate in genetics (1933) stated in 1925: "In the past we could have bred for greater resistance to cholera or disease; but it was quicker and more satisfactory to clean up the environment." Many fear that modern claims for a genetic basis of many social problems will serve as a smokescreen for "cleaning up the environment" by blaming societal problems on the "defective biology" of individuals.