Am J Biol Anthropol. 2026 Sep;191(1):e70359. doi: 10.1002/ajpa.70359.
ABSTRACT
Human reproduction presents features that appear inefficient in isolation: gamete overproduction, mechanically demanding birth, neonatal altriciality, lactational suppression of fertility, reproductive cessation, prolonged post-reproductive survival, and extensive care by individuals other than parents. Evolutionary accounts increasingly explain such features through conflict among parties with divergent fitness interests. We argue that conflict loses discriminating power when the term is extended to physical limits, to cooperative interactions, and to trade-offs within a single organism, and that this loss occurs as a formally derived concept becomes a framing metaphor in synthetic and applied literatures. We set out an explanatory architecture in which four processes-genetic conflict, constraint, cooperative dependence, and life-history allocation-occupy distinct positions within a single optimization structure: constraint specifies the feasible set and the shape of the benefit and cost functions, allocation identifies the optimum for one party within it, and conflict and cooperative dependence describe how many parties hold optima on the same joint phenotype and whether their marginal interests oppose or align. A cross-cutting temporal dimension covers traits whose consequences fall on one individual at more than one time. We restate conflict as a claim about marginal rather than total fitness returns, so that shared benefit neither establishes nor refutes it. Explicit coding rules assign nine phenomena a primary architecture and contributing processes, with evidence status, standing in the literature, and discriminating predictions. Two worked cases-the obstetrical dilemma and lactational amenorrhea-convert contested labels into separable empirical programs. The framework does not settle these questions; it specifies which measurements would.
PMID:42733193 | DOI:10.1002/ajpa.70359
