ARE WE HARDWIRED? THE ROLE OF GENES IN HUMAN BEHAVIOR

Authors William R. Clark and Michael Grunstein obviously have a remarkably extensive background in genetics. Even their list of over 200 references, conveniently listed by chapter, covers 17 pages. Clark is Professor Emeritus in the Department of Molecular, Cell and Developmental Biology at UCLA, and Grunstein is Professor of Biological Chemistry, also at UCLA.

Research reports from single cell organisms to the latest twin studies are summarized. It is a fascinating story, told in easy to read language. Genetic influences on aggression, learning, memory, sexual preference, human "sixth sense," neurotransmitters, free will, substance abuse, and considerably more are analyzed.

The "nature vs. nurture" question is discussed in detail. The authors' answer is that both are important, and that one interacts with—not opposes—the other. They present scientific evidence that combinations of genes have much more impact on any one behavior than has usually been considered.

One wonders how long it will be before science, using genome mapping, will learn how to improve all human behavior. Don't guess the answer before you read this book; the time may arrive sooner than you think.

• In the laboratory, rats and mice have been selectively bred for many generations to create strains that are fearful or aggressive. These strains pass on their personality differences each time they breed. No one seriously questions the role of genes in the development of animal behavior, or of inheritance in passing these traits from one generation to the next. Yet we are reluctant to acknowledge a similar role of genes in guiding human behavior.

• Genetic variation may affect not only our responses to the environment, but our very perception of it in the first place.

• Surprisingly, numerous studies of twins, and both biological and adopted siblings, have shown that shared home experiences have a minimal effect in shaping the personalities of children....The similarities in siblings reared together appear to derive mostly from their shared genetic inheritance, and not from the home environment.

• The type of aggressive behavior associated with low serotonin is impulsive, rather than premeditated, aggression.

• We can destroy our children's natural mental abilities, but we cannot improve them. We may wish it were different, and intuitively we may think it should be different, but at the present time there are simply no data suggesting that it is. We can provide a secure and culturally enriched environment that will allow each child to optimize his or her innate abilities, but we cannot fundamentally alter these abilities.

• [A] parent and an adopted child are no more likely to score the same on an IQ test than two randomly selected unrelated individuals, even after many years of a close family relationship. A parent and a biological child, on the other hand, are much more likely to score close to one another—even when the child is adopted out at birth, and the parent and child are tested only later in life.

• Heritability patterns for substance abuse correlate strongly with heritability of other personality factors. Among individuals seemingly predisposed to substance abuse there is a higher than normal frequency of individuals manifesting impulsive behaviors, such as attention deficit disorders, thrill seeking, aggressiveness, and gambling, among others. There is also a strong correlation of substance abuse with negative emotionality, including personality parameters such as neuroticism, anxiety, and alienation.

• [A]lthough language, cognition, and culture make all human behaviors more complicated to dissect, there is no reason to believe that the basic causes underlying human aggression are different from those we see in other animals, or that genes play a greater or lesser role in regulating aggressive behavior in humans than in other animals.

• Each of us must struggle to maximize the genetic hand we have been dealt, played in the context of the environment into which we are born, against a certain level of indeterminacy we must somehow learn to bring under control. It is this struggle that defines us, and makes us human.

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