Blogs > Stone Age Brain | Rick Shenkman > Do our genes determine how we behave? Nah.

Mar 25, 2015

Do our genes determine how we behave? Nah.

tags: Genes

This is worth reading.  It's an article by Julian Baggini in the Guardian that explains why we should not leap to the conclusion that because genes are important, they are all-important, in determining behavior.


... The launch in 1990 of the Human Genome Project, which aimed to map the complete sequence of human DNA, came at the beginning of a decade that would mark the high point of optimism about how much our genes could tell us. Daniel Koshland, then editor of the prestigious journal Science, captured the mood when he wrote: “The benefits to science of the genome project are clear. Illnesses such as manic depression, Alzheimer’s, schizophrenia, and heart disease are probably all multigenic and even more difficult to unravel than cystic fibrosis. Yet these diseases are at the root of many current societal problems.” Genes would help us uncover the secrets of all kinds of ills, from the psychological to the physical.

Ten years later, Bill Clinton and Tony Blair were among the guests gathered to “celebrate the revelation of the first draft of the human book of life”, as Francis Collins, the director of the Human Genome Project, put it. “We try to be cautious on days like this,” said the ABC news anchor, “but this map marks the beginning of an era of discovery that will affect the lives of every human being, with implications for science, history, business, ethics, religion, and, of course, medicine.”

By that time, genes were no longer simply the key to understanding health: they had become the skeleton key for unlocking almost all the mysteries of human existence. For virtually every aspect of life – criminality, fidelity, political persuasion, religious belief – someone would claim to find a gene for it. In 2005 in Hall County, Georgia, Stephen Mobley tried to avoid execution by claiming that his murder of a Domino’s pizza store manager was the result of a mutation in the monoamine oxidase A (MAOA) gene. The judge turned down the appeal, saying that the law was not ready to accept such evidence. The basic idea, however, that the low-MAOA gene is a major contributing cause of violence has become widely accepted, and it is now commonly called the “warrior gene”.

In recent years, however, faith in the explanatory power of genes has waned. Today, few scientists believe that there is a simple “gene for” anything. Almost all inherited features or traits are the products of complex interactions of numerous genes. However, the fact that there is no one genetic trigger has not by itself undermined the claim that many of our deepest character traits, dispositions and even opinions are genetically determined. (This worry is only slightly tempered by what we are learning about epigenetics, which shows how many inherited traits only get “switched on” in certain environments. The reason this doesn’t remove all fears is that most of this switching on and off occurs very early in life – either in utero or in early childhood.)

What might reduce our alarm, however, is an understanding of what genetic studies really show. The key concept here is of heritability. We are often told that many traits are highly heritable: happiness, for instance, is around 50% heritable. Such figures sound very high. But they do not mean what they appear to mean to the statistically untrained eye.

The common mistake people make is to assume that if, for example, autism is 90% heritable, then 90% of autistic people got the condition from their parents. But heritability is not about “chance or risk of passing it on”, says Spector. “It simply means how much of the variation within a given population is down to genes. Crucially, this will be different according to the environment of that population....

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