Born Human: How The Utterly Dependent Survive

Session Date: 
Feb 21, 2014

Hominin infants who needed to elicit care and provisioning from allomothers as well as mothers confronted a different set of challenges from those faced by their last common ancestor with other apes. Reliance on allomaternal assistance to rear young rendered mothers increasingly sensitive to signals of how much social support she and her offspring could expect, and multiple offspring with overlapping periods of dependency meant 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. Elsewhere I hypothesized that such an "unapelike" rearing system led immatures to develop novel phenotypes that over generations were subjected to directional social selection (sensu West Eberhard) favoring youngsters who at birth demonstrated good survival prospects and who over the course of development proved adept at monitoring the intentions, thoughts and feelings of potential caregivers so as to engage and appeal to them. Here, I rely on the best available proxies we have for humankind’s last common ancestor with other apes (studies of chimpanzee and modern human infants) in order to test a key underlying assumption of this "Mothers And Others" model -- that contingent care from multiple others generates ape phenotypes with more fully expressed other-regarding potentials. In this way, without any foresight on Mother Nature's part concerning future pay-offs, raw material could become available for Darwinian selection to favor enhanced mutual understanding in the line of apes belonging to the genus Homo.

File 2014_02_21_10_Hrdy.mp4107.3 MB