On human parental investment termination
MetadataShow full item record
Neglect or murder of someone’s own child is often viewed as an unnatural act. However, it is also seen in non-human mammals. From an evolutionary viewpoint it could be beneficial to terminate investment in a specific offspring, in order to invest in other current or future offspring. Abortion, resorption, infant neglect and infanticide are the means to accomplish this. We reviewed literature to see whether investment termination occurs under comparable circumstances in human and non-human mammals, and whether its occurrence can be explained evolutionary by the current investment termination models. The models predicting parental investment were the additive, contingent, male quality, competition for restricted resources, local resource enhancement, advantaged-daughter and the population adjustment model. All but the contingent and additive model could be distinguished based on characteristics of the infant most likely to suffer investment termination and of the caretaker that terminates investment. Important characteristics are resource availability, litter quality, parenthood certainty, environmental safety, caretaker condition, caretaker rank, infant fitness, infant sex, condition dependent sex, dispersing sex, equilibrium sex ratio and current sex ratio. Studies measuring at least some of these factors were scarce, none measured all. In most studies the additive/ contingent model best predicts the parental investment termination patterns observed, but this is also due to a lack of data required to test alternative explanations. The majority of primate studies on neglect were better predicted by an alternative, possibly maladaptive hypothesis; neglect occurs more often in primiparous females that lack maternal experience. No difference was observed between species with different breeding styles. The additive/ contingent model may be the best model of investment termination in all species, or most incomplete studies could fit to it because it is the broadest model. In order to test what is the case new studies are needed, measuring the described factors plus maternal experience.