The Evolution of Difficult Childbirth and Helpless Hominin Infants

摘要: Because of the implications for behavioral, social, and cultural evolution, reconstructions evolutionary history human parturition are driven by two main questions: First, when did childbirth become difficult? And second, does difficult have something to do with infant helplessness? Here we review available evidence consider answers these questions. Although definitive timeframe remains unclear, may not reached our present state difficulty until fairly recently (<500,000 years ago) body brain sizes approximated what now, or perhaps even more because agriculture's direct indirect effects on growth development both mother fetus. At present, there is little indicate that has affected evolution gestation length fetal growth, selecting infants born in a supposed underdeveloped state, although phenomena likely share causes.