What You Can Change _. And What You Can't - Martin E. Seligman [22]
Andy is a terrible two. Steven, his father, beats him whenever Andy throws a tantrum—not just a spanking: Black eyes and broken fingers result. Once Steven starts, he can’t stop. Andy’s crying eggs his father on, and Steven doesn’t stop until Andy is whimpering quietly. All this came out when Andy’s mother took him, suffering from a “fall,” to the emergency room. Steven was arrested.
Steven was mercilessly beaten by his own father through most of his childhood, and Steven remembers his father claiming to have been beaten by his own father when he was a boy.
Social scientists tell us that this cycle of child abuse is learned. Steven learned to beat Andy by being beaten by his father, and his father learned it the same way. It is quite possible that the children of abusers beat up their own children more often than do children who were not beaten up by their parents. But this evidence is equally compatible with another theory, one that is so unfashionable as to be omitted as a possibility by the social scientists who discovered the generational transmission of child abuse.16
What evolution works on. The alternative explanation is that aggression is inherited, and that more aggressive people have “more aggressive genes.” People who beat little children are loaded with them, this theory suggests. If these little children are the abusers’ biological children, they will, in turn, grow up aggressive—not because they “learn” anything while being beaten, but because they inherit their parents’ aggressive tendencies.
Does Steven beat Andy because he inherited an aggressive disposition (which he has passed on to his doubly unfortunate son), or did he learn to beat up children from his own childhood beatings? How can this question be answered?
We are used to the idea of genes controlling simple characteristics like eye color. But can something complex, like a personality trait—aggression, for example—be inherited? To approach this question, it is useful to think about evolution: What does evolution work on and what gets selected?
I believe that genes, the particular molecular string of DNA, and simple traits like eye color are selected only indirectly. These get selected because their owner is more successful at reproducing and surviving than the owners of different strings of DNA. What gets directly selected, however, are the characteristics that cause their owner to outreproduce and outsurvive the competition. It is complex, “molar” traits like beauty, intelligence, and aggression that are the primary material of natural selection, which cares only about “modules,” the traits that lead directly to reproductive success. This means that complex trait selection is the normal mechanism of evolution.
Molecular biology has it backward. This field looks exclusively at simple traits and molecular building blocks (DNA strings), which can be measured—respectable, quantitative science. But this does not mean that nature is at all interested in simple traits or their molecular constituents, or that the inheritance of simple traits illuminates the inheritance of the more fundamental, complex traits.
Evolution, for example, has certainly worked on the complex trait of “beauty,”17 which is passed on from one generation to the next, as is the propensity to be attracted to it. Natural selection sees to it that attractive people have higher reproductive success than people less so. Beauty in turn is made up of traits like eye color, and eye color in turn has building blocks—for example, a particular chain of DNA. But beauty, like automobiles, comes in many models, and its definition changes within limits over time and culture. There are many ways to be attractive: many combinations of eye color, teeth, and hair. More important, a greater number of combinations will be ugly and will thus be eliminated from the gene pool. If there are myriad kinds of