Human Pair-Bonds: Evolutionary Functions, Ecological Variation and Adaptive Development

Stable mating relationships are widespread in our species, with important economic, social and reproductive implications. 1 Pair-bonds are part of the unique human mosaic including very large brains, childhood, concealed ovulation, sexual intercourse in private, cultural symbols, and complex social groups. Yet we understand relatively little about the evolution of human pairing, its functions, and consequences for human diversity. We can define pair-bonds as the long-term affiliation of two individuals including a sexual relationship. The important point is that the union is relatively enduring whether monogamous or polygamous. Recent debate about human pair-bonds highlights apparently conflicting hypotheses: Are pair-bonds the evolutionary consequence of male mating competition or are they an adaptation for paternal provisioning? 4,5 Unfortunately a simple answer seems unlikely. The evidence indicates selective pressures from mating competition and provisioning needs, suggesting different benefits of pair-bonds in different contexts. Whether a bond emphasizes mating or parenting effort may depend on environmental cues. Childhood experience evidently affects pair-bond development, suggesting further adaptive design for flexible life history strategies. Functional and developmental accounts of pair-bonds rarely converge, but cross-fertilization could stimulate advances. Here I review theory and data for pair-bond functions, before turning to the development of human pairing behavior in a life history perspective. The approach here is to examine primate comparisons, cross-cultural analyses, and ethnographic case studies. The goal is develop refined hypotheses for human pair-bonding through the convergence of existing data.