Sex-biased parental investment in primates

Parental investment enhances an offspring's chances of survival concomitant with reducing the parent's ability to invest in other offspring. Three main models might explain the conditions under which parental investment is expected to be sex-biased, but accurately testing the models is difficult. At least 7 fundamental issues remain unresolved in the area of parental investment in primates. The central dilemma is trying to gauge how the process improves the survival and reproductive prospects of current progeny at the expense of the survival or fertility of the parent. No single model is likely to be applicable to all primates. Parental investment probably operates in a condition-dependent framework designed to maximize lifetime reproductive success, but whether sex-biased investment occurs in an adaptive fashion remains unresolved.