Although epidemiological data provide evidence that early life experience plays a critical role in human development, the mechanism of how this works remains in question. Recent data from human and animal literature suggest that epigenetic changes, such as DNA methylation, are involved not only in cellular differentiation but also in the…

Investigated genetic change and continuity within the domains of temperament, emotion, and cognition and language for 200 pairs of twins assessed at 14 and 20 months of age. Correlations of measures at the two ages indicated that individual differences in the second year of life showed greater change than continuity on most measures. (MDM)

Posits that an evolutionary perspective can unite the study of the typical development for and individual variation within a species and that environments within the normal range for a species are required for species-normal development. Individual differences in children reared in normal environments arise primarily from genetic variation and…