This paper discusses recent scientific research that has shifted the terms of the debate about the respective roles of nature and nurture in shaping behavior. The research includes literature in the areas of biology, psychometrics, evolutionary psychology, and behavioral genetics. The paper then shows the relevance of this literature for ongoing concerns about mass immigration in developed countries. The literature has implications not only for the personal success of the immigrants, but rates of social dependency and the outlook for political and social cooperation in increasingly diverse societies. Efforts to remediate IQ deficits or behavioral problems in some immigrant groups are seen to be problematic.