The Implications of Epigenetic Research for the Study of History

How rapidly can humans respond physiologically to changing historical conditions? For decades, most observers thought adaptation was a slow process, which could occur only over many generations as natural selection winnowed populations of individuals with maladapted genes in favor of individuals with better adapted (or at least neutral) genes. There is great truth to that observation. Many adaptations, such as the capacity to digest milk into adulthood or to resist malaria, involved changes in the human genome that evolved over generations. But in recent decades, biologists have discovered that physical adaptation to changing conditions can in some instances occur more rapidly, within a single individual’s life, and can occur without changing the genome. Such adaptations are possible because of the crucial role played by the molecules and proteins that clothe our genes and determine which genes are switched on or off. Epigenetics—the study of non-genetic substances that affect the functioning of the genome—has made important strides in recent decades, particularly in the study of cancer and human development. But can epigenetic changes have an impact on human behavior and consciousness within a single lifetime? And can those changes be inherited from one generation to the next? These questions are at present stirring intense debate among biologists. But promising research indicates that epigenetics will have profound implications for historians. My paper will consider the epigenetic forces that determine the production of hormones and hormone receptors, which may leave us more or less capable of feeling pleasure, tolerating stress, or cooperating with others. It will conclude with a plea that we embrace a less reductionist approach to historical explanation, one that considers the interaction of social and cultural forces with biological forces.