Speaker

Herman Pontzer
Jerry G. and Patricia Crawford Hubbard Professor of Evolutionary Anthropology
Duke University

Abstract

The global collapse in fertility rates poses a challenge to both economic and evolutionary models of human reproductive behavior. I develop a model of fertility, integrating evolutionary and economic approaches, that focuses on the costs and benefits of reproduction. The model derives offspring as positional goods, whose utility is entirely dependent upon their quality relative to the average quality of other offspring in the population. The model also derives adult quality as a positional good, its value dependent upon the average quality of other adults. Model predictions are for parental investment, offspring quality, and fertility are supported across a wide range of mammal species. As human populations transitioned from subsistence economies to industrialized economies, biological limits to offspring investment and adult quality were removed. The loss of these limits enabled a positive feedback loop favoring every greater offspring quality and adult quality, resulting in continuously declining fertility.