The Influence of Heredity

The isolation studies discussed above may seem to suggest that inheritance can be dismissed as a factor in the social development of humans and animals. However, the interplay between heredi­tary and environmental factors is evident in two fascinating studies that began to produce results in 1987—one involving pairs of twins reared apart and the second examining the inheritability of a form of mental illness.

Inheritability and Traits of Twins The case of Oscar Stohr and Jack Yufe, discussed at the be­ginning of the chapter, is a dramatic example of two genetically identical persons who neverthe­less developed quite different personalities and political values—presumably because of their dif­fering socialization experiences. By contrast, an­other pair of identical twins reared apart, Jim Springer and Jim Lewis, both chain-smoke the same brand of cigarettes, chew their fingernails, drive the same model blue Chevrolet, and have owned dogs named Toy (Leo, 1987).

Researchers at the Minnesota Center for Twin and Adoption Research are studying pairs of identical twins reared apart to determine what similarities, if any, they show in personality traits, behavior, and intelligence. Thus far, the prelimi­nary results from the available twin studies indi­cate that both genetic factors and socialization experiences are influential in human develop­ment. Certain characteristics, such as twins' tem­peraments, voice patterns, and nervous habits, appear to be strikingly similar, thereby suggest­ing that they may be linked to hereditary causes. However, there are far greater differences be­tween identical twins reared apart in terms of atti­tudes, values, types of mates chosen, and even drinking habits. In examining clusters of person­ality traits among such twins, the Minnesota stud­ies have found marked similarities in their ten­dency toward leadership or dominance, but significant differences in their need for intimacy, comfort, and assistance.

Researchers have also been impressed with the similar scores of twin pairs on intelligence tests. Most of the identical twins register scores even closer than we would expect if the same person were to take a test twice. At the same time, how­ever, identical twins brought up in dramatically different social environments score quite differ­ently on intelligence tests—a finding that sup­ports the impact of socialization on development (S. Begley et al., 1987; Holden, 1987b; Tellegan et al., 1988).

Inheritability and Mental Illness Lancaster County, Pennsylvania, is hardly a likely site for scientific breakthroughs. Often the destination of tourists, this area is best known for its Amish communities—whose distinctive subculture was popularized in a 1985 Hollywood film, "Witness." For 10 years, a team of psychiatrists and biologists (Egeland et al., 1987) studied the occurrence of manic-depressive behavior in three generations of Amish families. Victims of manic depression (or bipolar affective disorders) shift between the ex­treme emotional states of euphoria and depres­sion. In studying this illness, scientists found that the Amish served as an excellent sample. Their communities keep accurate genealogical records; moreover, many environmental factors which contribute to manic depression, such as alcohol­ism, drug abuse, unemployment, and divorce, are extremely rare within the Amish subculture.

The findings of the Pennsylvania study suggest a certain hereditary basis for manic-depressive behavior, which is apparently linked to genes in the specific region of a chromosome. The re­searchers emphasize that this genetic characteris­tic neither guarantees nor precludes manic de­pression; they can only report that persons with the characteristic show a predisposition to manic-depressive behavior. It should be noted that this degree of specificity was not present in the twin studies discussed earlier. There was no sugges­tion, for example, that a single gene could be linked to timidity (Goleman, 1986; Wallis, 1987; Woller, 1987).

In reviewing the studies of twin pairs and the Amish, one should proceed with some degree of caution. Janice Egeland, head researcher for the Amish study, notes an encouraging aspect of findings which point to the importance of hered­ity in human development. "Too often," she ar­gues, "personal embarrassment and social stigma are associated with an illness whose cause is be­yond the control of the individual." By contrast, Princeton University psychologist Leon Kamin fears that overgeneralizing from the Minnesota twin results—and granting too much importance to the impact of heredity—may be used to blame the poor and downtrodden for their unfortunate condition. As the debate over nature versus nur­ture continues, we can certainly anticipate nu­merous replications of these fascinating investiga­tions to clarify the interplay between hereditary and environmental factors in human develop­ment (Leo, 1987; Wallis, 1987:67).

Sociobiology

As part of the continuing debate on the relative influences of heredity and the environment, there has been renewed interest in sociobiology in recent years. Sociobiology is the systematic study of the biological bases of social behavior. Sociobiologists basically apply naturalist Charles Darwin's principles of natural selection to the study of social behavior. They assume that partic­ular forms of behavior become genetically linked to a species if they contribute to its fitness to sur­vive (van den Berghe, 1978:20). In its extreme form, sociobiology resembles biological determin­ism by suggesting that all behavior is totally the result of genetic or biological factors and that so­cial interactions play no role in shaping people's conduct.

Sociobiology does not seek to describe individ­ual behavior on the level of "Why is Fred more aggressive than Jim?" Rather, sociobiologists focus on how human nature is affected by the genetic composition of a group of people who share certain characteristics (such as men or women, or members of isolated tribal bands). In general, sociobiologists have stressed the basic genetic heritage that is shared by all humans and have shown little interest in speculating about al­leged differences between racial groups or na­tionalities.

The current debate on sociobiology focuses on the work of Edward (Wilson 1975, 1977, 1978), a zoologist at Harvard University. Wilson does not deny the importance of socialization and therefore is not an extreme biological determinist. He does, however, go further than most social scientists by emphasizing the influence of hered­ity on behavior.

Many social scientists have strongly attacked the main tenets of sociobiology as expressed by Wilson and other theorists (C. Campbell, 1986; Kitcher, 1985). Some researchers insist that intel­lectual interest in sociobiology will only deflect serious study of the more significant factor influencing human behavior—socialization. Yet Lois Wladis Hoffman (1985), in her presidential ad­dress to the Society for the Psychological Study of Social Issues, argued that sociobiology poses a valuable challenge to social scientists to better document their own research. Interactionists, for example, could show how social behavior is not programmed by human biology, but instead ad­justs continually to the attitudes and responses of others.

The conflict perspective shares with sociobiol­ogy recognition that human beings do not like to be dominated, yet there the similarity ends. Conflict theorists (like functionalists and interac­tionists) believe that social reality is defined by people's behavior rather than by their genetic structure. Consequently, conflict theorists fear that the sociobiological approach could be used as an argument against efforts to assist disadvantaged people, such as schoolchildren who are nol competing successfully (Caplan, 1978; M. Harris, 1980:514).

In the view of feminist Arleen Rogan (1978:85), sociobiology "opens the door to justify­ing the oppression of one group by another on the basis of biological inferiority." This warning is not without foundation. Already in Singapore, a bustling westernized country in soul beast Asia, parents with less than a college education are rewarded if they agree to be sterilized after the birth of their first or second child. At the same time, parents with degrees are given incentives to have more children. Prime Minister Lee Kuan Yew promotes this policy by declaring that grad­ual genetic deterioration will cause Singapore's national "levels of competence" to decline (Well­born, 1987:62).

Wilson has argued that there should be parallel studies of human behavior with a focus on both genetic and social causes. Certainly most social scientists would agree with the sociobiologists' contention that there is a biological basis for social behavior. But there is less support for the more extreme positions taken by certain advocates of sociobiology (Cove, 1987).

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