Blame genes, maybe that wild streak runs in the family

A growing understanding of human genetics is prompting fresh consideration of how much control people have over who they are and how they act. The recent discoveries include genes that seem to influence whether an individual is fat, has a gift for dance or will be addicted to cigarettes. Pronouncements about the power of genes seem to be in the news almost daily, and are changing the way some Americans feel about themselves, their flaws and their talents, as well as the decisions they make.

For some people, the idea that they may not be entirely at fault for some of their less desirable qualities is liberating, conferring a scientifically backed reprieve from guilt and self-doubt. Others feel doomed by their own DNA, which seems less changeable than the more traditional culprits for personal failings, like a lack of discipline or bad childhoods. And many find it simply depressing to think that their accomplishments might not be the result of their own efforts.

Because tests for the genes that influence personality and behavioural traits are not yet commercially available, there is no way for most people to know which ones they have. And even if they could, the newly uncovered genes are thought merely to influence, not determine, their personalities. Biologists are also quick to emphasise the role environment plays in activating genetic dispositions that might otherwise never be expressed, or mitigating those that are.

But that has not stopped people from acting on their assumptions. The public embrace of genetics may be driven as much by wishful thinking as scientific truth. In an age of uncertainty, biology can appear to provide a concrete answer for behavior that is difficult to explain. And the faith that genetics can illuminate the metaphysical aspects of being human is for some a logical extension of the growing hope that it can cure disease.

‘‘More and more stories about who we are and how we live are becoming molecular,’’ said Paul Rabinow, an anthropologist at the University of California, Berkeley, who studies the interrelation of science and culture. ‘‘The older liberal worldview that it’s all a question of willpower is still very present in America, but genetics has become a strong countercurrent.’’

That may be partly because the science has become more credible. Armed with the human genome sequence, along with a catalog of genetic variation in the human population, and tools that can inexpensively gauge any individual’s genetic makeup, scientists can now pinpoint the genes associated with inherited traits. Developed to dissect the genetic basis for complex ailments like heart disease and cancer, the methods are now being applied to less pressing areas like the way genes may influence sexual desire or attention deficit disorder.

While scientists have yet to demonstrate any genetic cause that directly affects such behaviour, they have found plausible associations. And for many people, that is all that matters. ‘‘The scientific facts have changed,’’ said Steven Pinker, a psychologist at Harvard who documented cultural resistance to the influence of genetics on behavior in his 2002 book The Blank Slate. ‘‘We now have real evidence that some of the variation in personality is inherited,’’ Dr Pinker said, ‘‘and I think it may be affecting people’s everyday choices.’’

AMY HARMON