you we've heard a lot this afternoon to remind us beginning with window this morning about how costly it is to rear human children and how much help mothers need don't forget that but this means that children are born in a world where they are depending on a wider cast of characters than I think evolutionary anthropologists had originally assumed and that's what you've been hearing about a lot today and whether that cast of characters whether the protagonists are fathers or others or grandmothers or whatever the human infant confronts all the same challenges that other Apes do
but both the mother and her infant are going to have to factor in this extra support from pre reproductive helpers from male helpers whether it's the father or whether it's this band of bros out there showing off grandmothers they have to factor in these extra concerns they are not able to count on the four to eight years of single-minded maternal dedication that a infant chimpanzee or orangutan might these infants were in competition with the mothers older children when they're born and those of you who have siblings know what that feels like they're also in competition
with their mothers alternative reproductive possibilities a baby that might be born at a better time the mother's mate has just left but she might get a new man and next baby born then and this leads to a very special challenge of humans and only a very few other primates of mothers discriminating between offspring possibly retrenching and as has happened I'm afraid all too frequently in human history and prehistory bailing out altogether contingent maternal commitment has increased selection pressures on babies to look good right at birth when mate mothers are making the initial decision before for
example picking that baby up where you can latch onto the nipples and do all those that wonderful magic with oxytocin so you heard when to say that babies are born fatter bigger than other Apes they're born five times fatter and it's true of course that this is helpful if there's a separation from the mother it helps to keep them warm but you know other Apes face that same challenge and yes it's true that you need to fuel that very rapidly developing brain but I suspect that's not the only reason human babies are born so fat
they're also producing an advertisement for their themselves they're saying hey mom I'm full-term robust I'm a good bet for survival keep me and being born full-term would have been even more critical among our Pleistocene ancestors with very high infant mortality there's a bottleneck there for hominin children that was very hard to get through and even though it's a lot easier today when 99% of the babies born in our society survive we see curious vestiges of this ancient preoccupation when we send out birth announcements with gratuitous information nine pounds three ounces why do we care looking
cute stimulates reward systems in human brains your orbital frontal cortex just fires off all sorts of good responses when you see a cute baby but let's analyze what cute baby means if you alter faces digitally from less to more cute and analyze it what cute baby means is plump alert healthy full-term a low parental brains respond pretty much the same way the initial results from studies like this was greeted by the media's oh we found the basis for maternal instincts but half the people in that study were males the majority all the women in this
study were no libris they never had a baby a low parents and parents have these same effects so fathers clearly have this potential to respond the babies and you have this species where mothers need help so very much in that case how is it that paternal care varies so much I mean you have some men who are totally dedicated to their children the mrs. Doubtfire out there and you have other men men certain of paternity who behave is just they didn't even know they had children how can this be I call this the paradox of
facultative fathering and you have this species where men have this extraordinary potential for nurture albeit not always expressed we know for example men in intimate contact with children with babies their prolactin level goes up another one of those female hormones that we didn't study so much and men because you know who would have thought you have oxytocin level going up you have testosterone going down all of this in response to infants and the relevant factors seem to be the signals of need from the infant very important the man's own own childcare experience did he have
experiences babysitting as a boy the man's relationship with the mother probability of genetic paternity but the most important of all is this prolonged element contact with infant and so you have this very facultative capacity for caring that were only in really in the last decade starting to learn more about and we're beginning to get information very relevant to this from hunter-gatherer people like the taka this is these are data from Cortney Meehan who's worked with Mary among the akka and what she learned was that men provide more or less direct care depending on a number
of factors but including importantly who else is there available and willing to help and she was able to do this by looking at couples when they were living in a mattre local setting surrounded by the mothers matrilineal kin and but and then she looked at couples living in a patrilocal setting where the mothers kin were no longer available now the amount of care the baby got direct physical holding didn't change and the amount of time the mother held her baby didn't change that much but what changed was in the Metro local setting the bulk of
a low maternal care was being done by the mothers matrilineal kin in the patrilocal setting all of a sudden dads were chipping in enormous lee they were needed they were they were already bonded to their babies and they responded well recognizing humankind deep legacy of cooperative breeding which just means any species with a low parental in addition to parental care and provisioning of young helps us resolve this curious paradox of the facultative father in addition to flexible family compositions which is very important in hunter-gatherer lives and very flexible residence patterns where and poorest social boundaries
where people can move between groups you also have to have something else though going on you need youngsters able to identify who's going to help engage and appeal to potential caretakers in a way that other Apes didn't have to do now they are not among Apes but among some of the other primates and many of the monkey species for example there's a great deal of infant sharing not infant provisioning necessarily but shared care of infant's that goes on but remember these infant sharing primates have had millions of years to evolve within this system and so
you have had infants evolved attributes that make them highly attractive not just to their mothers that's actually a foregone conclusion among monkeys but attractive to others as well so you have these bright golden babies you have these snow-white babies born to black and white parents humans of course we're the new kids on the block in terms of cooperative breeding we've had a mere two maybe three million years of doing this we don't have flamboyant natal coats to attract our a low parental caretakers but mothers take care of this they use culture and custom to decorate
their babies and we do it - that's what baby stores are about to get you to come in so if the key difference cognitively between humans and other Apes has to do with the kind of shared intentionality and triatic interacts something that Kim bard talked about earlier today if this is really a key difference and I think it is we still need to explain its initial emergence the initial development of these capacities and my own favored way of explaining it is to take a highly intelligent bipedal ape with the cognitive and manipulative potentials and rudimentary
theory of mind that we find in all the great apes just your run-of-the-mill last common ancestor and then rear that ape in a very novel social context where maternal care is contingent and the immature develops having to depend on elicit help from ingratiate him or herself with a range of caretakers and providers and as Kim bard described and I think hopefully convinced you of earlier today developmental context makes a big difference in how a little ape turns out at the end of development this doesn't say that and we know for a fact it doesn't that
if you rear a chimp in a human family it is like a human no but we know that it is phenotypically different and reasons to believe that accumulating evidence suggests that among our hominid ancestors children's survival is going to depend on a low parental input the care from others without a maternal care anyway hair from individuals other than the mother and provisioning so at the end of this very novel developmental period you then have Darwinian social selection that's going to favor any little immature in which the potentials for looking out to others and paying attention
to others that Kim bard finds in her Apes those potentials are more developed well you know you can have a wonderful trait but if it's not expressed in the phenotype it's invisible to natural selection by expressing these traits and that Darwinian social selection has a chance to favor those little immatures that just are just a little bit better at mind-reading a little bit better at ingratiating themselves with others well that's an interesting model but did contingent nurture affect phenotypic development the way this model assumes well it's the usual story we can't go back in time
we can't see how hominin children responded to caretakers 2 million years ago but we still have studies of living apes and we have studies a great deal of study in fact of their modern human descendants so I'm going to ask does being reared by Allah mothers in addition to mothers I want to be clear Mel and I don't differ on how important mothers are how central we do we might differ on the capacity of children to have multiple attachment figures but we don't differ on the importance of mothers does being reared by Allah mothers in
addition to mothers effect ape phenotypes the way the model assumes rendering youngsters more other regarding well we can look at chimpanzees as proxies for the last common ancestor exclusively reared by its mother or reared by mothers plus others albeit in many of these cases we're talking about human ala mothers and as Kim pointed out the ones reared with our mothers in addition to mothers are better reading certain social cues they get they read points better than do chimpanzees reared exclusively by their mothers we know from studies in Kyoto chimpanzees accustomed to trusted human caretakers test
better when they're asked to provide a another chimpanzee the tool that they need to get at a particular treat they can peek through see what this guy needs and hand them exactly that one behavioral evidence from modern human descendants babies off their mothers spend more time looking at faces monitoring I gaze they pay more attention to expressions than do the babies in continuous physical contact with their mothers greater reliance on alle mothers also may help explain why human infants are more interested in triatic interactions holding something else out at about nine months of age to
see what someone else thinks about it tominaga and others find that little chimps kind of lose interest in doing that whereas humans are getting better and better humans also like chimpanzees can recognize photographs of their mothers face right from birth or they learn shortly after but after a while chimpanzees lose this capacity and infant humans just get better and better at that decades of research in the social sciences document enhanced mentalizing and perspective-taking in children reared with multiple attachment figures I'm just going to mention a few of the highlights of at-risk mothers with a maternal
grandmother in the household with them have enhanced cognitive abilities their children are attached settar are more securely and the children exhibit enhanced cognitive capacities by age for the presence of older siblings is correlated with a more sophisticated theory of mind by age three and improved social skills at older ages lots of studies in that vein finally the involvement of multiple caretakers is correlated with an enhanced capacity to integrate multiple perspectives from as early as three to four months babies are also able to tell who's going to help who's going to hurt famous studies that I
Callie Hamlin I'm gonna have to skip through why do I believe that humans are better at doing this earlier then chimpanzees are I have no right to believe that in the sense that we have not looked yet at these capacities how early they emerge in humans the kind of thing Kali Hamlin was studying but the reason I suspect that humans are going to be better at it earlier is were coming out of the primate research institute in Kyoto - that's our omatsu Zayas group Sakai and her colleagues comparing brain development and finding that there's a
faster tragic Tori of growth in the white matter of the human prefrontal cortex that's the part of the brain where we're processing these kind of discriminations between other individuals things like who's going to be helpful and who's not what they're going to like and not the timing of this faster development in the human prefrontal cortex starts at around six months coinciding with emergence of attention-getting vocalizations and I think many people would argue well sure ser it's just language but I'm not so sure because of course I see babbling is just another way to get out
of maternal attention and language comes much later it also emerges at about the same time as milk teeth and the kind of kiss feeding that was very important among hominin foragers so human infants lag behind other Apes in physical development though I would argue that plump human babies are cute they lag behind other Apes in physical development yet they proved remarkably precocial in monitoring others and assessing their intentions so I want to just conclude with a slight caveat to the title on your program the helpless human turns out to be only selectively altricial and to
remind you that cooperative child-rearing has meant quite literally changing our minds thank you
