A comparative approach to maternal behavior in humans and other apes

In many species, including humans, maternal care is crucial for infants' survival and development. Here, we used a comparative developmental approach to investigate the factors that predict variation in primate maternal styles and, specifically, in the allocation of body contact, carrying, nursing, touching, grooming, restraining, rejection, object stimulation, approaches and leaves. We conducted behavioral observations on mother-infant pairs from the genus Homo (i.e., White German mothers: N = 10) and four other primate genera (Pan, Hylobates, Nomascus, Symphalangus: N = 38), when infants were 1, 6 and 12 months old. We observed that mothers partially adjusted their behavior to the offspring's age (decreasing some protective/proximal behaviors and increasing some rejective/distal ones as infants grew up), and to the potential risks experienced by offspring (with protective/proximal behaviors being often higher in Homo than Pan). Despite the limitations of only including captive ape groups, this work provides novel insight into the development of mother-infant interactions across five primate genera and contributes to our understanding of the evolutionary roots of human parenting behavior.