Insights from epigenetic studies on human health and evolution.

Epigenetic variation represents a unique aspect of human biological variation that can shed light on our evolutionary history as well as the etiology of human disease. DNA methylation is the most commonly studied type of epigenetic modification and can alter gene expression without changing the underlying DNA sequence. DNA methylation occurs throughout all living organisms although its function seems to have evolved from genome defense in fungi, bacteria and plants to a more complex role in gene regulation and cellular differentiation in animals. Human DNA methylation was originally studied in imprinting diseases and cancer, but more recently has been investigated as a mechanism to mediate the impact of environmental and psychosocial stressors on human health and disease.