Steven Pinker: ‘The common assumption is that voluntary genetic engineering is inevitable … I believe that it is not only not inevitable, but highly unlikely in our lifetimes.’ (Staff photo Rose Lincoln/Harvard News Office)

The genetic revolution has created tremendous excitement, but also considerable fear. As scientists identify the genes responsible for various traits and behaviors, and become more adept at transferring genetic material from one organism to another, there is growing anxiety that we are heading for a disturbingly unnatural and ill-considered future in which parents eager for their child’s success will have genes governing everything from hair color to musical ability injected into the developing embryo, resulting after several generations in radical changes to the human race.

It’s not going to happen, says Steven Pinker.

Pinker, the Johnstone Family Professor of Psychology, is known for his research on how humans acquire and use language, as well as for a series of best-selling books exploring more general aspects of human mental activity – “The Language Instinct” (1994), “How the Mind Works” (1997), and “The Blank Slate: The Modern Denial of Human Nature” (2002). On Nov. 30, he gave a talk sponsored by the Harvard Museum of Natural History titled “The Past, Present, and Future of Human Nature.”

True, Pinker said, there is growing evidence that humans are born with an intricate structure of mental and behavioral characteristics that is partly under genetic control, but this does not mean that parents will be opting for “designer babies” any time soon.

“The common assumption is that voluntary genetic engineering is inevitable considering the pace of genetic research and the fact that parents will want the best for their children, but there is also reason for skepticism. In fact, I believe that it is not only not inevitable, but highly unlikely in our lifetimes,” Pinker said.

First, there is the general fallibility of predictions about the future. The list of future breakthroughs that have failed to materialize include nuclear-powered vacuum cleaners, domed cities, routine consumer space flight, mile-high buildings, and refrigerators that automatically restock themselves. Too often futurologists extrapolate trends in a simple linear fashion without considering the costs of new technology (programming a self-stocking refrigerator may be more trouble than it’s worth).

Also, pundits whose predictions tend either toward hype or alarmism are more likely to gain the ear of the public. “A futurologist who said the future is probably going to be more or less like the present probably would not get much attention,” said Pinker.

One important reason the designer babies scenario probably won’t play out is the failure of scientists to find single genes with consistent beneficial effects.

“Anyone who has kept up with the literature on behavioral genetics has noticed that there’s been a widespread failure to find single genes for schizophrenia, autism, obsessive-compulsive disorder, and so on. And those, by the way, are the areas where we’re most likely to find a single gene simply because it’s easier to disrupt a complex system with a single defective part than it is to install an entire complex ability with a single gene. The failure to find a gene with a consistent effect on, say, schizophrenia, means that it’s even less likely that we will find a gene for something as complex as musical talent or likeability.”

There is also evidence that genes are not solely responsible for the expression of mental traits. Identical twins who are reared together share identical genes as well as a nearly identical environment, and yet on personality tests they show only about a 50 percent correlation. In some cases there are striking differences – one twin may be gay, the other straight, one may be schizophrenic, the other normal.

“What that tells us is that there is an enormous and generally unacknowledged role for chance in the development of a human being.”

Even if genes could be identified that consistently produce desirable characteristics, it is likely that undesirable traits may show up as part of the package. For example, by using genetic manipulation scientists have produced mice that have a superior ability to solve mazes, but these mice also turn out to be hypersensitive to pain. It is doubtful that parents would want to increase their child’s intelligence if it involved taking such a risk.

“On the one hand, we have the stereotype of competitive yuppie parents who will stop at nothing to enhance their child’s chances, but on the other hand, parents also have an aversion to harming their children. What percent of risk would you take to increase the chances of your child getting into Harvard?”

People’s choices are also affected by intuitions about contamination and naturalness, Pinker said, and these feelings would probably discourage the introduction of genetic engineering into human reproduction.

“If people have an aversion to genetically modified soybeans, it’s unlikely that they’d jump at the chance to have genetically modified babies.”

Moreover, producing a “designer child” would necessarily involve the use of in vitro fertilization, a traumatic, painful, and expensive process. “I think most people would prefer to conceive the old-fashioned way,” Pinker said.

Realistically speaking, even if genetic engineering were available to prospective parents, the choice they would face is certain to give a rational person pause.

“Would you opt for a traumatic and expensive procedure that might give you a very slightly happier and more talented child, might give you a less happy, less talented child, might give you a deformed child, and probably would do nothing?”

In view of all these drawbacks to the use of genetic engineering in humans, Pinker believes that bioethics policy needs to be reconsidered.

“Bioethics policy should acknowledge the frailty of long-term technological predictions which have a very spotty track record at best. Bioethics policy should be based on fact, not fantasy. Both our positive and our negative fantasies are unlikely to come true, and policies predicated on the inevitability of genetic enhancement should be rethought.”