It has long been known that an organism’s fate is not determined by genes alone. This much we can tell by observing identical twins, who over time tend to diverge both physiologically (developing differences in, say, height and posture) and psychologically (exhibiting different personality traits and even, sometimes, sexual orientations). Despite most identical twins having similar diets and lifestyles, subtle cultural and environmental distinctions appear to alter their phenotype—the sum of their nature and nurture. In 1942, Conrad Waddington coined the term “epigenetics” to describe this idea that an organism’s experience may cause its genes to behave (or “express themselves”) differently. Scientists have found striking examples of epigenetic behaviour in the animal kingdom—in the way, for example, honeybee larvae “decide” whether to become queens or workers depending upon their interaction with other larvae and the environment.

Until recently, it was assumed that the impact of epigenetics was confined to individual organisms, and was not passed on to their offspring. Epigenetics was thought of as the cross-talk between genes and environment, giving individuals some adaptive capability in their lifetimes, but not beyond. Recently, though, scientists have become convinced that there is a form of inheritance, called epigenetic inheritance, in which the behaviour of genes in offspring is affected by the life experience of parents. Furthermore, these epigenetic changes can, at least for a small minority of genes, extend beyond immediate offspring to further generations, although the effects do not appear to last indefinitely. This discovery has a number of potential implications, both good and bad. On the one hand, it may give renewed impetus to health authoritarians and revive the discredited theory of Lamarckism (the idea that how we live alters our genes). On the other hand, it could provide scientists with the means to fill in important gaps in the story of evolution.

There is also the possibility that epigenetic inheritance is implicated in the passing down of certain cultural, personality or even psychiatric traits. For instance, historical “insults,” such as Oliver Cromwell’s brutal reconquest of Ireland in 1649, have led to an “embedding” of attitudes within the affected communities that persist for generations. However, it has generally been thought that this phenomenon could be explained by Richard Dawkins’s theory of memes, according to which cultural or intellectual traits are passed down via non-genetic mechanisms such as storytelling. The possibility raised by epigenetics is that such cultural transmission may, after all, have a genetic component. Could it be that historical traumas, such as transatlantic slavery, leave some kind of genetic mark on the descendants of their victims?

• Share
•  Subscribe to post comments