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For instance, Bygren's research showed that in Overkalix, boys who enjoyed those rare overabundant winters--kids who went from normal eating to gluttony in a single season--produced sons and grandsons who lived shorter lives. Far shorter: in the first paper Bygren wrote about Norrbotten, which was published in 2001 in the Dutch journal Acta Biotheoretica, he showed that the grandsons of Overkalix boys who had overeaten died an average of six years earlier than the grandsons of those who had endured a poor harvest. Once Bygren and his team controlled for certain socioeconomic variations, the difference in longevity jumped to an astonishing 32 years. Later papers using different Norrbotten cohorts also found significant drops in life span and discovered that they applied along the female line as well, meaning that the daughters and granddaughters of girls who had gone from normal to gluttonous diets also lived shorter lives. To put it simply, the data suggested that a single winter of overeating as a youngster could initiate a biological chain of events that would lead one's grandchildren to die decades earlier than their peers did. How could this be possible?
Meet the Epigenome
The answer lies beyond both nature and nurture. Bygren's data--along with those of many other scientists working separately over the past 20 years--have given birth to a new science called epigenetics. At its most basic, epigenetics is the study of changes in gene activity that do not involve alterations to the genetic code but still get passed down to at least one successive generation. These patterns of gene expression are governed by the cellular material--the epigenome--that sits on top of the genome, just outside it (hence the prefix epi-, which means above). It is these epigenetic "marks" that tell your genes to switch on or off, to speak loudly or whisper. It is through epigenetic marks that environmental factors like diet, stress and prenatal nutrition can make an imprint on genes that is passed from one generation to the next.
Epigenetics brings both good news and bad. Bad news first: there's evidence that lifestyle choices like smoking and eating too much can change the epigenetic marks atop your DNA in ways that cause the genes for obesity to express themselves too strongly and the genes for longevity to express themselves too weakly. We all know that you can truncate your own life if you smoke or overeat, but it's becoming clear that those same bad behaviors can also predispose your kids--before they are even conceived--to disease and early death.
The good news: scientists are learning to manipulate epigenetic marks in the lab, which means they are developing drugs that treat illness simply by silencing bad genes and jump-starting good ones. In 2004 the Food and Drug Administration (FDA) approved an epigenetic drug for the first time. Azacitidine is used to treat patients with myelodysplastic syndromes (usually abbreviated, a bit oddly, to MDS), a group of rare and deadly blood malignancies. The drug uses epigenetic marks to dial down genes in blood precursor cells that have become overexpressed. According to Celgene Corp.--the Summit, N.J., company that makes azacitidine--people given a diagnosis of serious MDS live a median of two years on azacitidine; those taking conventional blood medications live just 15 months.