Scholars using evolutionary theory in the social sciences (mostly outside of sociology) were the first to draw attention to inequalities in outcomes between children from single parent/other types of families and children from two biological parent families, and inequalities in outcomes between biological children and nonbiological children in families. There is now much evidence from sociology and other social science disciplines that outcomes on many metrics (including mortality, education, and adult income) are less favorable on average for children from single parent/other types of homes than for children from two biological parent homes. Scholars using evolutionary theory were also first to note the increasing inequality in fertility between lower income and higher income individuals (particularly men) in rich world countries. In rich countries around the world, lower income men are more likely to remain single and childless. In many countries in recent birth cohorts, lower income women are also more likely to remain single, although women are less likely to remain childless than men. The ability of evolutionary theory to help explain and predict these growing inequalities is an important reason why sociologists should incorporate the use of evolutionary theory in sociology alongside the traditional sociological focus on more proximate mechanisms and determinants.
Rosemary Hopcroft (Mon,) studied this question.