An Aka husband customarily resides for a time with his wife and her family. The new husband will hunt on their behalf for a period of years (known as “bride service”) until one or more children have been born. Thereafter, the couple may stay, move with their children back to his people, or in some cases join another group altogether. The practice of remaining near the wife’s kin until after children are born means that inexperienced young mothers are likely to be among their own kin when they give birth for the first time, an especially vulnerable time for mothers and even more vulnerable for firstborns. Across primates, infants born to inexperienced, first-time mothers are at high risk of death from, among other causes, maternal inexperience and incompetence. Like all first-time primate mothers, only more so, young women need extra support and guidance as they learn to mother.63 As she expected, Meehan found that a mother residing around her own mother and her mother’s kin (that is, living “matrilocally”) does indeed receive a great deal more assistance.
Even with small sample sizes, differences were large enough for Meehan to identify a clear pattern. Infants whose mothers lived matrilocally received more than twice as much alloparental care as infants born to mothers living near their husband’s kin (“patrilocally”). Care from older siblings was a constant for infants living in both locations. The difference was the extra help provided by an infant’s maternal aunts and uncles and especially by its maternal grandmother. When interviewed, all but two Aka women specifically mentioned that they preferred living in their natal community because of the availability of kin support.
To Meehan’s surprise, the total amount of care an infant received did not differ much in the two settings. This was so even though mothers themselves spent about the same amount of time holding their babies. How could this be? The question brings us back to fathers. In the absence of mother’s kin, fathers compensated by caring more. Meehan found that in patrilocal settings, fathers were doing nearly 20 times more caretaking.64 This flexibility provides the key to the paradox of facultative fathering. Care is a fungible commodity, and humans have always been unusually flexible and opportunistic not just in eliciting care but also in providing it, relocating, adjusting, juggling, and compensating in strategic ways.
Over the long span of human evolution, even if a dad defaulted, alloparents could—at least potentially—fill the yawning chasm between what children needed and what their mothers alone could provide. In some situations, death or defection of the mother’s mate would doom their offspring. Undoubtedly, huge numbers succumbed. Yet if humans evolved as cooperative breeders, theirs had to be a dynamic system with built-in flexibility. If, instead of being a devoted dad, a father turned out to be only an indifferent nurturer, or even if he deserted altogether, decamping to seek alternative mates, his offspring still might pull through with help from alloparents, permitting a “cad” to enjoy his cake and reproductive fitness too. Cynical as all this sounds, there is a growing body of empirical evidence about the psychology of fathers and the behavior of alloparents consistent with such a scenario. Flexibility was, and continues to be, the hallmark of the human family.65
STRATEGIC FLEXIBILITY
Even though Hadza fathers are typically indulgent and just as affectionate with their children as Aka fathers are, the only time they hold infants is when they are in camp, and they do so much less of the time, closer to 7 percent than to 22 percent.66 Yet even among the Hadza, anthropologists Alyssa Crittenden and Frank Marlowe found a similar pattern to the one Meehan described for the Aka: With or without a dad present, a Hadza infant’s quota of direct alloparental care remains more or less constant.67
Once again the explanation has to do with how flexible, opportunistic, and also mobile the Hadza are, readily moving where they are needed or where they need to be. If a father died or defected, a Hadza infant’s grandmother was more likely to come to live nearby and spend more time holding her fatherless grandchildren.68 When fathers were alive and well and living in the same camp, they accounted for a quarter of all non-maternal caretaking, holding babies twice as often as the babies’ grandmothers did. But when the father was absent, the amount of time maternal grandmothers held grandchildren increased, rising to 70 percent of the time that someone other than the mother held infants. If the mother remarried so that children were living with a stepfather, grandmothers again stepped into the breach, moving nearby. In this situation, the proportion of time infants were held by grandmothers rose to 83 percent of the total time they were held by nonmaternal caregivers.69
In other words, the effects of father absence are attenuated through proactive and strategic maneuvering by kin, especially by the mother’s mother, as well as through the mother’s own maneuvering.70 We’ve already seen how mothers may strategize by lining up extra fathers even before a child is born. But mothers have other options as well. For example, when the !Kung woman Nisa lined up one too many extra fathers and her jealous husband opted for a Bushman divorce by simply leaving, Nisa trekked across the desert to join her distant brother. She remained with her child’s maternal uncle while she looked for another mate willing to be a stepfather to her children.71 Of course, having a surviving older brother willing to help her rear his nieces and nephews is not much more certain than having a husband. And as we will see in Chapter 8, the availability of a grandmother is less certain still.
The higher the mortality risks, the less either a mother or her slow-maturing children can afford to depend on any specific family composition and the more critical it becomes for children and their parents to be flexible in eliciting support. If a parent dies, it becomes more crucial than ever for collateral kin or older siblings to compensate, and evidence suggests that they often (alas, not always) do. When Patricia Draper, a child development expert, joined forces with Nancy Howell, a demographer, to study growth rates of Ju/’hoansi children using data collected when the Bushmen still lived as nomadic foragers, they found that children, though hardly well-nourished, grew at fairly constant rates regardless of fluctuations in the precise configurations of kin on hand to provision them. Draper and Howell speculated that this smoothing out of food availability was due to the sharing ethic typical of hunter-gatherers, combined with the residential flexibility of parents and alloparents.72 By 2005 Lawrence Sugiyama and Richard Chacon documented just such a pattern among Yora forager-horticulturalists of southeastern Peru. On average, weaned juveniles spent about 40 percent of time eating in households other than their own. But in the case of juveniles with only one living parent, they were more likely to be found in households with more alloparents, presumably buffering them against parental loss.73 In such a system, the children most at risk from paternal defection are going to be those short on alloparents.
Most hunter-gatherers live in close-knit family units. To this extent, conventional views about family life among our ancestors are correct. But the composition of these families fluctuates through time. What we idealize as the nuclear family (father, mother, and their children) was often just a temporary phase, a less-than-optimal phase at that, since by themselves two parents would have been unable to meet the needs of several children. In describing the typical or natural Pleistocene family, the descriptors I prefer are kin-based, child-centered, opportunistic, mobile, and very, very flexible. Childrearing units were inherently elastic, expanding and contracting as individuals gravitated away from adversity and toward not only food and water but locations where either they anticipated social support or had reason to expect that their support was needed by other family members. These alloparental safety nets provided the conditions in which highly variable paternal commitment could evolve.
The seeming paradox posed by Darwinian selection—favoring mothers who produced children beyond their means, paired with fathers whose help is far from guaranteed—actually represents two sides of the same coin. On either side, the paradox is resolved the same way. Mothers can overshoot their capabilities to provide, and fathers can vary, because both sexes evolved in a hig
hly fluid system where alloparents often provided the compensatory assistance.
BIOLOGICAL UNDERPINNINGS OF DADS VS. CADS
In my book Mother Nature I analyzed the combination of love and ambivalence in the maternal side of the human parental equation. Here I have focused on the paternal side, on the variable devotion of fathers and on the role that cooperative breeding played in the evolution of such facultative care. It’s time to consider biological mechanisms involved in determining whether a man will behave like a dad or a cad.
A January 3, 2007, news story in the New York Times described two men in the Bronx who rushed forward to catch a boy falling from a fourth-floor window, saving his life.74 When the second of the two men, Pedro Nevarez, who had a 19-year-old foster son, was interviewed afterward, he modestly asserted that “I’m not a hero. I did what any other father would do. When you’re a father, you would do this whether it’s your child or not.” Mr. Nevarez was making an important point about the relevance of experience. Thresholds vary, but men who have lived with and come to love small children are more likely to feel a reflexive urge to rescue a child, even one who does not share his genes. At the same time, there are innumerable cases where even a father confident in his paternity behaves as if he is oblivious to the well-being of his own children. The extremely variable nature of men’s nurturing impulses makes it essential to consider the experiential as well as the social and ecological conditions under which paternal devotion emerges.
Take two foraging societies, the !Kung San and the Aka. Both are characterized by affectionate fathers with relatively high certainty of paternity.75 Yet !Kung fathers engage in little direct care of infants (holding them maybe 2 percent of the time), while Aka fathers engage in ten times that much. According to Hewlett, the difference may be explained by opportunities for male-infant proximity. Whereas !Kung men go off with other men for long periods while hunting, Aka men use nets to hunt game and go off as a group together with wives, children, and others. Aka (and also Efe) men spend a lot of time around camp and have more leisure time to interact with infants and children. Obviously, feeling more certain about paternity will be a common corollary of a husband accustomed to spending time in close proximity to his wife. But certainty about paternity, which has been such an obsessive focus for evolutionary interpretations of male behavior, is only one factor influencing men’s nurturing responses to babies. Time spent in proximity with pregnant women and their infants and the act of caring for babies, in and of themselves, render men—even a man who is not the genetic father—more nurturing. Thus far (in Chapters 3 and 4) I have paid more attention to the effects of cooperative breeding on the well-being of mothers and their infants. Let’s briefly consider the experiential, endocrinological, and neurological effects on males—men and boys alike.
In contrast to !Kung fathers, who spend relatively little time holding infants, and do so only when in camp, Aka fathers spend more time holding infants both in camp and when both parents go on hunting expeditions in the forest, as shown here. (Barry Hewlett)
Endocrinological transformations during pregnancy, birth, and lactation, as well as neurophysiological responses to the powerful stimuli babies emit, are far more pronounced in mothers than in fathers. But men as well as women can be physiologically altered by exposure to babies. Prolactin, a hormone commonly associated with brooding behavior in female birds and lactation in mammals, provides a case in point.76 Prolactin levels in men residing in intimate association with pregnant women or new babies are significantly higher than those in other men. Other hormones linked to maternal sensitivity to infants, such as cortisol, also rise in fathers when they are in contact with pregnant mothers and subsequently with their newborns. On the other hand, testosterone levels fall.77 Not surprisingly, such changes are correlated, since fathers who are more involved during pregnancy also tend to be fathers more involved in caring for the baby during the first year of life.78 The more prior childcare experience a man has had, the longer he has been exposed to babies, and the more emotionally involved and sensitive to their needs he is, the more pronounced the physiological effects tend to be.
Some wags attribute higher prolactin levels in new fathers to sleep deprivation, a familiar stressor for new parents. Sure, sleeplessness could be a factor, but there has to be more to it. In one preliminary study, Hewlett found that just a mere 15 minutes of holding an infant could produce measurable increases in a man’s circulating levels of prolactin.79 Furthermore, such prolactin effects are more pronounced in experienced fathers holding their second-born infant against their chest than in less-experienced men, possibly because experienced fathers are presensitized. Such men also hold babies more.80
These correlations are most pronounced in species with biparental care, extensive shared care, or full-fledged cooperative breeding. They are found both in mammals, where of course only females lactate, and in birds, where neither sex does. Among scrub jays, pigeons, voles, marmosets, hamsters, and humans, higher prolactin levels are associated with nurturing behaviors by males. Calibrations differ by sex, of course, with levels especially high in lactating mothers. Nevertheless, the association between prolactin levels and nurturing holds across birds and mammals, both males and females, parents and nonparents, allomothers as well as mothers.81
In the first study of its kind, Canadians Katherine Wynne-Edwards, a zoologist, and Anne Storey, a psychologist, recruited 34 couples by requesting volunteers from prenatal classes at a hospital in Newfoundland. Couples were then visited at home and blood samples taken. Men in the study tended to have higher levels of prolactin and cortisol in the last three weeks prior to birth than was the case earlier in the pregnancy. Furthermore, stimuli from newborns produced further transformations as determined by a clever experimental design involving a second blood sample.
The first blood sample was taken shortly after the researchers arrived; the second was taken after the (probably bemused) subjects had been bombarded with the scent, sounds, and sight of newborn babies. Men were requested to hold either their own newborn or, if prepartum, a soft doll wrapped in a blanket that had recently held (and still smelled like) a newborn baby, while listening to tape recordings of a neonate crying inconsolably. Next, subjects watched a brief video of a newborn struggling to breastfeed for the first time. The men were then asked how they felt about their wife’s pregnancy and about the crying baby (for example, they were asked how anxious they were to comfort it).
Strong reactions to an infant in need were disproportionately exhibited by men who experienced couvade symptoms during their partner’s pregnancy. This term comes from the French couver (to incubate or hatch) and refers to various cultural practices whereby a man whose wife is pregnant or in labor displays physical symptoms similar to hers. Couvade symptoms range from weight gain and fatigue all the way to morning sickness and loss of appetite. Men most affected by their mates’ pregnancy, as well as those most responsive to babies, had the highest prolactin levels and the most pronounced declines in testosterone.82
Endocrinological researchers are at pains to point out that such hormone changes, by themselves, do not necessarily cause males to behave in nurturing ways.83 Rather, fluctuations in hormone levels—themselves influenced by particular behaviors and past personal histories—enhance male sensitivity to infant cries and other cues. This is one of the take-home messages from the work of University of Toronto psychologist Alison Fleming, who together with her colleagues has been working for years to tease apart the complex interactions between biological and social factors that influence parental responsiveness.84
Fleming’s early work focused on mothers, but as she expanded her experimental field of vision to include fathers’ responses as well, her team discovered interesting similarities—and differences. Their results show that “not only do the cries produce changes in fathers’ hormones, but fathers’ endocrine states prior to hearing the cries are related to how they respond to those cries. Fathers with lower baseline testosterone leve
ls are more sympathetic and show a greater need to respond.” As in mothers, hormones function in conjunction with past experiences and experiential cues to alter the chances that a male will respond in a nurturing way. When Fleming combined endocrine measures with behavioral observations of men whose past childcare histories were well known, she discovered that the more previous caretaking experience a man has had, the more pronounced the hormonal changes turned out to be.
Again, this is not to say that women and men are equivalent in their responses. Transformations in mothers are far more dramatic. Scientists have to use a completely different calibration to measure the hormonal changes in the two sexes, and rather than responding to internal cues from pregnancy and the birth process, men must depend on as-yet-unidentified sensory cues from the mother or baby. Furthermore, thresholds for responses to a fretting infant are set lower in new mothers than in new fathers.85 All the same, it is increasingly clear that a biological potential for nurturing behaviors lies latent in some if not all men—even though it takes particular conditions and past experiences to induce the behaviors, and even though the potential is only sometimes expressed.86
To date, the most widely replicated hormonal effects have to do with a drop in testosterone levels reported for men living in close association with pregnant women and for men living with infants after they are born.87 The more responsive to infants men are, the more likely their testosterone will continue to drop with continued childcare. It makes me fantasize about bottling essence of neonate to spray about the rooms of teenage boys.
Mothers and Others Page 19
