Twin, sibling, and adoption methods. Tests of evolutionary hypotheses.

Twin, sibling, and adoption studies have long been used by behavioral geneticists to identify genetic and environmental influences underlying human behavioral and physical variation. The full potential of these methodologies for unraveling the blend of biological, cultural, and experiential factors affecting human development has been insufficiently appreciated. The application of twin, sibling, and adoption designs for examining hypotheses generated by evolutionary theory is described. Potential contributions from a closer association between these disciplines are underlined.