In the 21st century, infant and child mortality is lower, education takes longer, and people live longer and healthier lives. In this environment, the risk of death is lower, but the danger of falling behind economically is higher in an age of income inequality, so parents choose to have fewer children and nurture them more extensively. As an academic paper put it, “When competition for resources is high in stable environments, selection favors greater parental investment and a reduced number of offspring.”
