A handful of recent studies on oxytocin and parenting have been published by Ruth Feldman and colleagues in Israel. They have measured oxytocin levels in blood, saliva and urine. They found that "fathers with higher baseline [oxytocin] engaged in greater stimulatory physical play behaviors with their children, while men performing more tactile exploratory play with their infants showed larger short-term (15 min)[oxytocin] spikes than did other fathers."(p.4) In longitudinal analysis of fathers' (and mothers') blood oxytocin levels, even as men's oxytocin levels also increased in the months after having a baby. In the past few years, researchers have collected bodily fluids from olive baboons, gibbons and siamangs, measuring testosterone levels after forming a "friendship" with a female. "[C]aptivesiamang fathers experienced a significant decline in [teststerone] over the course of their offsprings' infancy, coinciding with stark increases in father-offspring interaction."(p.8) However, in the wild, fecal testosterone levels of male gibbons were higher in male-female pairs than male-male groups or in groups witha dependent infant. These examples suggest that male testosterone levels may be attuned to social variables-particularly a mate and offspring-in captivity and the wild. Based on research in other animals, including some fish, birds, and mammals, you might deawupon the multifaceted potential of prolactin to help regulate features of direct childcare. This could yield some convergences in the physiological underpinnings of paternal care in different lineages of primates (including the human primate).