Undetermined: there is danger in assuming that genes explain all

National Review, June 2, 2008 by Jill Manzi

THE delineation of the double-helix structure of DNA by Watson and Crick in 1953 will almost surely rank as one of the most epochal scientific discoveries in human history. Following rapidly upon the synthesis of Darwinian evolution with Mendelian genetics in the 1930s and '40s, it enabled a research program that now seeks to explain a vast array of physical phenomena, from the functioning of individual organisms to the development of species over geological time. This success has led some science popularizers to believe that we have found a new Rosetta Stone enabling us to understand many of the mysteries of human existence. But if translated into public policy, their belief would likely have disastrous results. In the coming decades, it will be important for conservatives to walk a fine line: on one hand, to resist such hubris; on the other, not to throw the baby out with the bathwater by denying valid biological science.

Driven by the genetic revolution, biology has displaced physics as the world's most important and exciting science. A substantial majority of all U.S. academic-research spending in science and engineering is now in life sciences. More than twice as many of the developed world's most widely cited scientific research papers are in the life sciences as are in physics and chemistry combined. Successful new scientific paradigms change how we see the world, and therefore exert intellectual influence well outside of the technical specialties that produced them. The more fundamental the paradigm, the wider and deeper are these radiating influences. In the case of modern biology, they are profound. Proceeding from the sociobiology movement of the 1970s, some biologists have sought to explain all individual behavior and social organization as the predictable result of genes-plus-environment. The reigning presumption of academic America is that over time this movement will sweep all before it.

This perspective inevitably trickles down into mainstream opinion. To choose just a few illustrative examples, within the past few months both Time and The New York Times Magazine have had cover stories on the evolutionary roots of morality; Time has had a second cover story on the biological basis of romance; Newsweek has had one article on the genetic explanation of psychological resilience and another arguing that varying incidences of disease-causing pathogens explain the degree to which different countries' policies are individualist or collectivist; NBC News has broadcast a story on the genetic basis for smoking addiction; ABC has had a story on the evolutionary origins of the incest taboo; and CBS has run a story titled "Eureka: Happiness Gene Found." Mass media are inundated with this biology-explains-all ideology.

OLD THOUGHTS, NEW ERRORS

Now, the idea that the vast majority of people share a set of stable, inherent characteristics--that is, the idea that there is such a thing as human nature--is not new. Nor are the subsidiary ideas that individuals have somewhat varying inborn natures; that this variation is partially heritable; and that individuals who share a lineage will demonstrate common traits and tendencies. All of these beliefs are at least several thousand years old, and probably predate written records.

What's new is that--because we believe that we have uncovered at least a component of the physical manifestation of human nature, in the form of the genome--many now believe that we can operationalize these old ideas: that we can explain the causes of the behaviors of individuals and groups sufficiently to predict these behaviors scientifically. Those who believe this, believe that we can remove the mind-body problem from the purview of philosophy by reducing the mind to a scientifically explained physical phenomenon. When pushed, such theorists will generally admit that we cannot yet do much of this, but will then state confidently that we "are starting to understand" or "are on the verge of explaining" various human behaviors.

Media outlets will often speak loosely of things such as a "happiness gene," a "gay gene," or a "smart gene." The state-ofthe-art method for finding such a link is something called a "genome-wide association study" (GWAS). In a GWAS, scientists use blood or saliva samples to sequence the DNA for a group of several thousand people who exhibit a trait or behavior of interest (the "case group"), and for a second group of several thousand who do not exhibit the trait or behavior (the "control group"). Scientists then look for genetic differences between the two groups. In cases where a single malfunctioning gene creates, for example, a catastrophic disease that overwhelms other genetic and environmental factors, a GWAS can quickly pinpoint the culprit. Sometimes, however, the behavior or trait is caused by several interacting genes--so that, for example, Gene 1 has some effect only if Gene 2 has a special structure. This is called "epistatic interaction," and can involve a large number of genes. Epistatic interactions make genetic effects harder to identify. Scientists deal with this problem and others by creating larger and larger case and control groups. The scaling up of such studies is among the most exciting frontiers in genetics. It is essentially an engineering problem, and money poured into solving it will likely improve human health through genetic screening and, ultimately, therapies.