Contributions and promise of human behavioral genetics.
Human behavioral genetics has contributed greatly to our understanding of human behavioral development. Twin, family, and adoption studies have shown that genetic effects are ubiquitous and that both genes and environments contribute to individual differences in behavior. The unique ability of behavioral genetic methods to separate genetic from environmental effects has also led to important discoveries about how the environment works in development and to the elucidation of the complex ways environments and genes interact across the life span. Although quantitative methods have been the mainstay of the field of human behavioral genetics since Galton's time, the Human Genome Project and advances in molecular genetics are providing new tools and promise as we enter the 21st century. Thus the future of human behavioral genetics lies in the cross-disciplinary exchanges and collaborations that will increasingly occur in the years to come among quantitative and molecular scientists who work with both animal and human systems. This research may someday culminate in an understanding of the biological basis of behavior that spans from how the brain develops and functions to a grasp of how genes influence thought at the molecular level.