Epigenetics and behaviour
The comprehensive sequencing of the human genome has generated great anticipation that by comparing the DNA sequence between individuals we will be able to understand the basis of phenotypic diversity between individuals, including the reasons for diﬀerences in behaviour such as diversity of levels of aggression amongst individuals. However, our current understanding of how the genome functions suggests that this might not be the complete story. The genome has to be programmed to express its unique patterns of gene expression. Diﬀerent cell types execute distinctive plans of gene expression, which are highly responsive to developmental, physiological, pathological and environmental cues. The combinations of mechanisms, which confer long-term programming to genes and could bring about a change in gene function without changing gene sequence, are termed here epigenetic changes. Thus, many of the phenotypic variations seen in human populations might be caused by diﬀerences in long-term programming of gene function rather than the sequence per se. Therefore, looking at sequence variations and polymorphisms per se might miss the mark. Thus, any future study of the basis for inter-individual phenotypic diversity should consider epigenetic variations in addition to genetic sequence polymorphisms (Meaney & Szyf, 2005).