Behavior

Heredity altered, coincidence denied

David Weinberger June 9 1980
Behavior

Heredity altered, coincidence denied

David Weinberger June 9 1980

Heredity altered, coincidence denied

Behavior

David Weinberger

Information like this was bound to capture headlines: Jim Springer and Jim Lewis, identical twins adopted as infants into different Ohio families, were reunited after 39 years and found that both had married and divorced Lindas and then married Bettys; both had had dogs named Toy; their sons were named James Allan and James Alan; both worked part-time as deputy sheriffs; their smoking and drinking patterns were almost identical. Even more startling is that they are not the only identical twins reared apart to report such coincidences. Dorothy Lowe and Bridget Harrison met for the first time at age 38, each wearing two bracelets on one wrist, a watch and a bracelet on the other, and a total of seven rings. The tale of another such pair, Oskar Stöhr and Jack Yufe, reads like the premise of a badly contrived morality tale: Stöhr was raised as a Hitler Youth in Germany and Yufe as a Jew in the Caribbean. Yet both flush the toilet before using it, dip buttered toast in coffee and enjoy sneezing in public.

Now scientists at the University of Minnesota, whose study of 15 such pairs has brought out these facts, have to separate the coincidental from the significant. Because of the increasing confusion in the scientific community over the issues raised—or not raised, according to some detractors—by recent studies such as this, the researchers are sure to find themselves in the midst of a centuries-old controversy. The question in dispute is as fundamental as it is vexing: how much of what we are is due to what we learn and how much are we born with?

This question—traditionally known as the “nature vs. nurture” debateraises itself today in issues such as intelligence and sex roles. Do we inherit our IQ or does it depend on how we are brought up? Are males innately more aggressive or is this a result of our culture? Identical twins raised apart seem to present a unique opportunity to answer these questions: they come from a single fertilized egg and therefore have exactly the same genes, the complex molecules that contain the “blueprints” by which an organism is constructed; they are the basic units of he-

redity. Since the genes are the same, any differences between twins raised apart should be due to their different environments, says Thomas Bouchard, professor of psychology at the University of Minnesota and head of the project.

However, the scientific community over-all is not as confident that the study will sort out what is due to heredity and what is due to environment. All agree with Bouchard that until the Min-

nesota study is completed (they have yet to process another 17 pairs of identical twins), nothing definite can be said. But, says Michael Ruse, professor of philosophy and history at the University of Guelph, “If this one [study] does come through, obviously it’ll be a very important body of information.” However, Ned Block, associate professor of philosophy at the Massachusetts Institute of Technology, has written that it may be misleading to generalize from what is learned about twins because “children given up for adoption cannot be supposed to be a random sample from the population.” In addition, he cautions that such studies can at best shed light only on what causes the differences between twins, not what causes similarities. If they have different political views, it is certain that

the views are not caused by their shared genes, but if they have the same political views, the twins studies will not explain why; it might be just coincidence or it might be the result of common environmental factors.

Bouchard and co-worker Irving Gottesman, a behavioral geneticist, find the headline-grabbing coincidences intriguing but not as promising as having found, for example, that some twins have similar headache patterns and

that some have put on weight simultaneously. Taken together with work done by Ronald Wilson, a psychologist and director of the Louisville, Kentucky, Twin Study, who has been keeping tabs on twins for more than 15 years, this suggests that there are some genetically controlled mechanisms that work on a schedule. Wilson, for example, has found evidence that mental as well as physical development comes in spurts that may be genetically regulated.

A fact such as the concordant number of rings worn by Lowe and Harrison would be more significant if a high percentage of twins also wear the same number of rings or if there is some way of accounting for the fact within genetic evolutionary theory. Ruse, from the University of Guelph, suggests that a genetic preference for flashy attire (spectacular creatures are more likely to attract mates and pass on their genes) might account for the twins’ preference for many rings. Bouchard speculates that since the twins have long fingers—a genetically controlled trait—and since our society values such fingers, the twins are likely to try to draw attention to them. Both explanations make the wearing of many rings significant by fitting it within an accepted theory. But, so far, no one has

come up with the reason why there should be a gene carrying the instruction, “Name your dog Toy.” It can be nothing but a coincidence, says scientists. Ruse explains, “There’s some evidence that even alcoholism may be genetic. But this doesn’t mean your preference for O’Keefe or Brador is hereditary.”

In any case, the whole heredity-environment question may be misleading, according to Block. Despite what most people, and even some scientists, think, Block says, “Something can be coded in the genes and yet be environmentally malleable.” Fear of heights may be innate-something people are born with—but this does not mean we cannot overcome it. Other genetic traits are much more resistant to change. But then, not only genetic traits but even some culturally taught traits are all but ineradicable: try, for example, to forget how to read. Just knowing that a trait is innate says nothing about how resistant to change it is.

Nothing demonstrates the confusion of innateness with inevitability more clearly than one of the most pernicious controversies of the 1970s, one that continues in this decade. Arthur Jensen, a professor of psychology at the Institute of Human Learning, University of California, fired the debate in 1969 by concluding that blacks in the U.S. score 15 points lower on IQ tests than whites because of their genes. His recently published book, Bias in Mental Testing, attempts to show that the point spread is not due to a cultural bias of the IQ tests.

Every aspect of his case has been attacked. Block and many others say the poorer environment of blacks is quite capable of explaining the difference in test scores. Stephen Jay Gould, professor of biology at Harvard, completely agrees with Block that Jensen is wrong to think that because something is geneti-

cally controlled (if indeed that is the case with IQ) it is not malleable. So, they say, even if blacks score lower on IQ tests for genetic reasons, it would be completely mistaken to conclude that higher education would be “wasted” on them, as some have concluded.

The same point about malleability may hold concerning the possible biological basis of different behavior of the two sexes. Typical is a recent book, The Evolution of Human Sexuality, by Donald Symons, professor of anthropology at the University of California at Santa Barbara. He gives reasons why men tend to be promiscuous and women tend to want more permanent relationships: a man betters his chances of passing on his genes if he mates often and with many women, whereas a woman stands a better chance if she attaches herself to a male who will protect her child after birth.

Theories such as these make a splash because the public, and sometimes scientists such as Jensen, seize on them for political purposes. Traditionally, conservatives have welcomed research that supports the idea that much behavior is innate, because, says Gould, “They take it to mean things are the way they are because people are made that way. It provides a reason not to fight the status quo.” Most scientists, however, think the political implications are not clear. Says Ruse, “There are very few scientific theories that couldn’t be used both ways.” Symons agrees and notes that the idea that nothing is innate could be used by the right as well as the left, for it would support the far right’s authoritarian ideal of being able to mould people into perfect conformists. But because the nature-nurture question is so dependent on theory, and because no theory has yet been firmly established, any new findings will be fiercely contested. Perhaps the chief point of agreement among the antagonists is that, though the research has no clear-cut political implications, they nevertheless will be drawn.