by Lori Andrews
This week’s Time features a cover story, “Why Your DNA Isn’t Your Destiny.” This is a far cry from the sentiment twenty years ago at the start of the Human Genome Project. At that time, a prominent psychiatrist announced, “The war is over in the nature/nuture debate” — implying that everything was due to genes (nature). Or when, during the Monica Lewinsky scandal, Time itself ran a cover story proclaiming “Infidelity–It May Be In Our Genes.”
In the intervening two decades, scientists have learned that human traits and behaviors are caused by a complex array of factors. When researchers begin searching for a gene related to height, they found variations at 20 different points in the genome that were related to a person’s stature. And even if all 20 were analyzed, that only accounted for 3% of the variation between people in height.
The limits of genes as explanatory factors — as well as curious questions such as why one identical twin can have schizophrenia or asthma and the other not — has led to a new scientific field, epigenetics. Rather than assessing genes, researchers are studying factors that influence whether genes are turned on or not. These factors can be entirely environmental. Time reporter John Cloud summarizes pivotal findings in his article: Pregnant woman who eat poorly produce children with a higher than average risk of cardiovascular disease. Boys who smoke before age 11 later created sons who were prone to obesity.
These effects on children are found even though there is no change to the genetic code. They appear to be caused by the addition of a methyl group (a carbon atom attached to three hydrogen atoms). When a methyl group attaches to a specific point in the genome, it can change the way the underlying gene is expressed. The National Institutes of Health is allocating $190 million in grants to explore “how and when epigenetic processes control genes.”
Back in 1997, Dr. Neil A. Holtzman and I predicted that genes themselves were not the whole story. In an article in Epidemiological Reviews, we highlighted the factors that make it difficult to explain complex conditions and behaviors in genetic terms. We noted that no more than five per cent of all cancer can be attributable to single inherited factors. And we also pointed out the downside of blaming everything on one’s genes.
“The emphasis on genetic causes,” we wrote, “leads to an approach that blames the victim and emphasizes the role of nonmodifiable genetic factors to the detriment of modifiable social and behavioral factors.” Hopefully, research in epigenetics will lead to new strategies of prevention and treatment outside of the genetics realm.