Sarah Blaffer Hrdy(UC Davis) discusses how reliance on allomaternal assistance to rear young rendered mothers increasingly sensitive to signals of how much social support she and her offspring could expect. Additionally, multiple offspring, with overlapping periods of dependency, meant that mothers might be forced to choose between offspring when investing. Paternal and alloparental responses to infants would also be facultatively expressed, depending on probable relatedness, alternatives available, past experience and degree of exposure to infantile appeals. (#28217)