Living With Our Genes: Why They Matter More Than You Think.

Living With Our Genes: Why They Matter More Than You Think. By Dean Hamer and Peter Copeland. New York: Doubleday, 1998, 355 pages. Cloth, $22.95.

Reviewed by Ray H. Bixler, Ph.D., University of Louisville, Department of Psychology, Louisville, KY 40292.

Pop art on the dust jacket provoked alarm--"Why did I agree to review a book like this!" The first few pages, including a quote from Popeye, intensified my discomfort. Having now read the whole work, I feel obliged to warn others not to judge this book by its cover.

Each chapter begins with the problems of one or more fictional characters used as jumping off points for lively discussions of topics such as worry, anger, and sex. This popular style, which should appeal to college students and other young adults, effectively conveys the subtle and complex interaction of heredity and environment.

Hamer and Copeland have produced a thorough survey of research and an excellent analysis of nature and nurture in determining behavior. Initially they play down the functions of rearing, education, and subculture. "We come in large part ready-made from the factory" (p. 11). Nevertheless, "genes are not fixed instructions ... (although) they do determine the range of what is possible" (p. 12).

In their introduction to "Behavior Genetics" the authors emphasize that parents should be aware that unique hereditary predispositions play a prominent role in the development of their children. Each child should be assisted to develop his/her own unique potential. It follows that we must avoid trying to mold them to meet our expectations rather than their own.

Studies of the behavior patterns of identical and fraternal twins illustrate the importance of heredity in determining behavior. Identical twins, whether reared together or in different families, are much more likely to exhibit similarities in behavior than are fraternal twins reared together.

We are introduced to the O'Rourke brothers, Charles and Michael, who exhibit striking differences in novelty-seeking behavior in spite of being reared in the same environment by the same parents. Hamer and Copeland then trace the research that led to the discovery of the specific genetic determinants of novelty-seeking. We are warned, however, not to forget that differing environmental influences almost certainly had an effect on the brothers. Like all the illustrations this is presented in an engrossing manner, comprehensible to lay as well as professional readers.

The chapter on "Worry" surveys the history of attempts to adapt by those whose behavior is dominated by persistent shyness and unjustified fears of being harmed. The importance of genetic factors is buttressed by animal studies in which the amygdala has been demonstrated as crucial in the experience of fear.

Hamer and Copeland cite the suicides of Ernest Hemingway and his siblings as suggestive of the role of heredity in depression, but quickly--and properly--note the fact that just because a trait "runs in the family doesn't necessarily make it genetic" (p. 66). Studies of identical and fraternal twins sharply reduce this confusion. References to research by several investigators (including Adam Matheny and David Wechsler, both of whose names are misspelled in the text and index) document the role of heredity in human boldness and shyness.

An explanation of the function of the brain chemical serotonin in the reduction of tension is illustrated by Sally, whose severe depression did run in the family (and here the authors clearly assume this to be genetically significant). She was effectively treated with Prozac. Serotonin's role in reducing violent behavior is impressively documented with summaries of research with both animals and humans.

"Anger" is introduced by involving the reader in a series of events, which begin with "Just as you are clearing your desk to pick up your son at the day-care center ..." (p. 87). One frustrating, demeaning act after another lead to the amygdala taking over the role normally played by the cerebral cortex. Hamer and Copeland believe that in these circumstances the worst one can do is to follow the advice of psychotherapists who urge us to vent our anger. Instead, they recommend turning the other cheek. There is substantial evidence, however, contradicting this advice. For example, children often adapt much better to their young siblings after having pummeled a baby doll in play therapy (Bixler, 1949).

The authors contend that the combination of heredity and environment, not either alone, determines whether one will become violent. This is technically correct, of course, but also misleading. Heredity and environment have a multiplicative, rather than additive relationship. If either is abysmally bad, it overwhelms the influence of the other. A bit later we are told that environment has little effect if one's heredity is "good"; however, environment is crucial if pathological heredity is involved. In this chapter Hamer and Copeland give very brief, but effective, coverage of fear, contending it prevents our behaving in ways which endanger our survival.

Research involving identical and fraternal twins in Asia, Europe, and North America provides striking evidence that heredity plays a less important role in the commission of crimes in childhood than it does later. "What puts kids in juvenile hall is mostly their environment, but what puts men in jail is more their genes" (p. 101). The choice of "men" should not be viewed as sexist: All over the world the commission of murder by males is more than 20 times the female rate.

The biological component for much of this difference appears to be hormonal. Research has revealed that testosterone levels not only differ between the sexes, but also between the most aggressive males and those whom they dominate. Confirmation of the prominent role of testosterone is provided by the unique status of female hyenas. Unlike most other females, they dominate their partners and, not incidentally, have extremely high levels of testosterone (Hrdy, 1981).

Having demonstrated what clearly seems to be the commanding role of heredity, the authors recoup in part by citing evidence that parental behavior, especially bad parenting, has a significant effect on children. Puzzling, however, is the illustration documenting the role of environment. It could just as easily be employed to support the role of heredity: Abused kids tend to be abusive of others.

Drug addiction is effectively described by presenting evidence that those addicted to one drug are very likely to become slaves to other drugs as well. For example, more than half of alcoholics smoke and more than two thirds of drug addicts abuse alcohol. Analyses of addiction in experiments with infrahumans provide provocative evidence in support of a strong genetic component.

Research has also demonstrated that alcoholism is much more common in the offspring of alcoholics than in the offspring of teetotalers. This holds true even when the latter are adopted by alcoholics and the offspring of alcoholics are adopted by nondrinkers. As one should anticipate, an identical twin is twice as likely to be alcoholic if his twin is alcoholic than is the fraternal twin of an alcoholic.

Last, but most important, nicotine is examined. Today, almost everyone is aware of the addictiveness of tobacco. The fact that susceptibility to addiction is genetically based is far less well recognized. This addiction is intensified by smoking's unique psychobehavioral components. Hamer and Copeland do not adequately emphasize the marked individual differences in addiction. While some are able to stop smoking after, at most, a few days of discomfort, the genetic makeup of others makes cessation of smoking unbearable. Those who claim anyone who really wants to can quit, citing themselves as evidence, benefit from a fortunate genetic makeup but not one noted for its humane or intellectual qualities.

The first pages of the chapter "Sex" would lead the reader to suspect this is a pornographic treatise, but the rest of the chapter is excellent. The role of hormones is employed to explain the monogamy of the prairie vole. The Coolidge effect (Wilson, 1982) and homosexuality are responsibly described. Hamer and Copeland conclude that heredity is a major and indisputable determinant in the sexual orientation of men, but for women "genes seemed to count hardly at all" (p. 189).

They summarize their own successful effort to map the genetic determinants of male sexual orientation. An area on the X chromosome (Xq28) appears to be relevant. Only 22% of the heterosexual brothers of gay males had the same Xq28 pattern, a striking deviation from the 50% that would occur by chance. Xq28 does not affect the sexual orientation of women.

"Thinking," the chapter in which intelligence is reviewed, evoked memories of my training many years ago (1940-41) in IQ test administration. If a child had taken the test in the past, and that result varied six or more points from his/her current IQ, one of my professors demanded that we give the test a third time to determine which of the previous scores was correct. Hamer and Copeland offer numerous illustrations that serve to demonstrate how ridiculous this requirement was. Intelligence does have unambiguous and important genetic determinants, but a child's potential will be achieved only if he has an ideal environment, broadly defined to include nutritional and health components as well as intellectual ones.

Hamer and Copeland fearlessly tackle the data on race and IQ. Their implied conclusion, that environment accounts for the differences between racial groups, clearly goes beyond that which can be derived from available data. The causes of racial variations in IQ can not be established as long as there is a clear correlation between IQ scores and the social, intellectual, and physical experiences of the races in childhood. Whether all, or only some, of the differences in the average IQs of Americans of Asian, African, and European origin is a result of the dramatic differences in their rearing can not be determined through correlational studies. Although "IQ is substantially heritable" (p. 234) these authors do, however, emphasize our lack of knowledge regarding the complex components involved.

Obesity, a common American affliction, is illustrated by chubby Sandra's weight problems, which began in early childhood, survived her repeated crash dieting efforts and led to her early death. Later, the authors return to Sandra. Wanting to refer to this earlier illustration, I turned to the index. "Sandra" was not listed. Checking further, I found that none of the other fascinating people used as illustrations are indexed. Hamer and Copeland stress that the potentially obese can control their diets and avoid becoming dangerously overweight. When we evolved as a species, obtaining sufficient food to assure survival was an extremely time-consuming struggle. As a result, genes which served to encourage us to eat were selected for. Unfortunately, these genes still control our appetites. The discussion of hunger concludes with a brief section on overeating and the disorders anorexia and bulimia.

By the time I reached the chapter "Aging" I anticipated an accurate yet novel analysis. I was not disappointed: "We die from planned obsolescence" (p. 274). I should add, however, that the authors seem to imply that our dying rather than living long after we can no longer reproduce is selected because of its advantage for our species. This theoretical position, group selection, is thoroughly incompatible with Darwinian natural selection theory. Evidence that there is a strong genetic component in both human and infrahuman longevity is presented responsibly as well as colorfully. Basic personality changes little as we age. On the other hand, character can change. Hamer and Copeland cite research demonstrating that the older we become, the more likely we are to help others and even to become more honest. Many also become more religious.

The last chapter begins with a discussion of the cloning of Andrew, an event that takes place shortly after the coming millennium. His father inserts cells from his own mouth into a human egg from which he has removed its own DNA. The "fertilized" egg is then implanted in the womb of the lab assistant who provided the egg. The offspring of this procedure is a healthy male who is technically his father's identical twin. The authors explain that they created this farfetched story to emphasize the phenomenal progress being made in understanding and controlling genetic processes.

Hamer and Copeland contend--I believe, correctly--that it is too late to wonder if we should manipulate the genetic determinants of our behavior. Rather, we must quickly decide how this technology is to be employed. They warn us that genes merely predispose, but do not assure, expression of particular patterns of behavior and personality.

Andrew reappears as an adult, with a doctorate in philosophy. He and his wife want children, but are concerned because she has a schizophrenic brother. Their physician assures them that DNA screening will eliminate genetic flaws. As a result, they know more about what their children will be like than any previous generation. "Andrew understood better than anyone what this information meant: very little" (p. 316).

REFERENCES

Bixler, R. (1949). Limits are therapy. Journal of Consulting Psychology, 13, 1-11.

Hrdy, S. (1981). The woman that never evolved Cambridge, MA: Harvard University Press.

Wilson, G. (1982). The Coolidge effect: An evolutionary account of human sexuality: New York: William Morrow and Company, Inc.

Michael R. Steveson, Ph.D.

Department of Psychological Sciences Ball State University Muncie, IN 47306, USA