Sunday, January 15, 2012

Of Chimps and Men: Males—What Are They Good For?

Sarah Blaffer Hrdy has written a fascinating book providing a view of how humankind evolved and diverged—perhaps over a million years ago—from the other great apes: Mothers and Others: The Evolutionary Origins of Mutual Understanding

Hrdy castigates early anthropologists (mostly male) for being so easily misled by recent history and by simplistic comparisons with other apes that they derived a male-dominated evolutionary scenario. In her words, the conventional wisdom became:

" Darwinian circles these days the most widely invoked explanation for how humans became so hypersocial is to stress how helpful within-group cooperation is when defending against or wiping out competing groups. We are told again and again that ‘the human ability to generate in-group amity often goes hand in hand with out-group enmity’."

"....from the early days of evolutionary anthropology to today’s textbooks in evolutionary psychology, the tendency has been to devote more space to aggression and our ‘killer instincts’ or to emphasize ‘demonic’ chimpanzeelike tendencies for males to join with other males in their group to hunt neighboring groups and intimidate, beat, torture, and kill them."

That is not a pretty picture of males in action, but it is at least...manly?

Hrdy’s hypothesis was discussed in Of Chimps and Men: Mothers and Others. She proposes that the key to human evolution lies in the development of cooperative breeding practices in which infants and children were nurtured by an extended group of caregivers. This freed the mother to spend more time gathering food and allowed her to give birth again before the child matured. The latter characteristic aided the survivability of the species. This form of childcare placed social burdens on the infants and children. They had to learn to read the intentions and emotions of others and learn how to elicit nurturing responses from others than their mother. Developing this capability was necessary for the survival of human infants in a way that was not replicated in other ape species. In other words, humans evolved to be the large-brained, organized animals we are today because we first developed the social skills that allowed the nurturing of the slowly maturing, voracious beasts, we were becoming.

The nurturing found in Hrdy’s early groups had to be female centered. Having another female who could hold and provide nourishment to her hungry infant when necessary would have been a great benefit for the mother, and a lifesaver for the infant. The most efficient form of organization for these early hunter-gatherers would be matrilocal—a mother associated with her mother, and other kin.

One might be wondering about the role of the father of the infant in this scenario. Hrdy introduces us to the general role of males in nature.

"To put men in perspective....across all 5,400 or so species of mammals in the world. In the majority of them fathers do remarkably little beyond stake out territories, compete with other males, and mate with females. With outlandish auditory and visual displays which often entail specially evolved weaponry, bellowing, barking, or roaring, males engage in fierce contests to route their competitors. Then ‘slam bam thank you ma’am’ and the inseminator is off. Male caretaking is found in only a fraction of mammals. By comparison, males in the order Primates stand out as paragons of nurturing, unusual for how much protection and even direct care of young they provide."

In Hrdy’s history, males developed a nurturing response, but one that was not driven strongly by the survival needs of the infant. The net result was that a variety of responses and behaviors are exhibited by males, both between species and within a species. On one extreme is the frightening habit of male infanticide—a significant cause of death in some ape species. Because mother apes lactate for many years in caring for their offspring, males, particularly from outside the immediate group, can become impatient and decide to kill the mother’s baby as the quickest means to render her fertile again. On the other end of the spectrum is a small primate species in which the father spends so much time fondling the infant that it bonds with the father rather than with the mother.

A more representative picture from apes and human hunter-gather societies might have the male hanging around the mother and new infant for a while and assist in providing food, at least initially. It then will wander off, but remain part of the group. It will remain aware of its offspring and will tend to protect the infant from harm if it can. If the mother can care for the infant without his assistance he will concentrate on his hunting and other group-specific chores. If the mother is having problems he will tend to devote more attention to nurturing responsibilities.

The human male is then left with an equivocal role, and an uncertain behavior pattern—one that is characterized by a complex genetic heritage rather than one determined by a highly selected response. Human males have genetic links to the species capable of infanticide as well as to those capable of a smothering nurturing behavior

"Some primates exhibit very high levels of direct male care, others do so only in emergencies, while still others exhibit no care at all. But the extent of this between-species variation pales when compared with the tremendous variation found within the single species Homo sapiens."

What we arrive at are human males who exhibit a variety of responses towards fathering and nurturing—from complete indifference to compulsive concern. Hrdy refers to this phenomenon as facultative fathering. Rather than the response being hard wired, men’s nurturing tendencies can be elicited by circumstance.

Hrdy reminds us that we must not forget that men also have a shared genetic heritage with the females of the species. Fathers exhibit some of the same physical responses that females undergo during pregnancy and at birth. The responses are at a lower level, but still strong enough to be correlated with changes in behavior.

" as well as women can be physiologically altered by exposures to babies. Prolactin, a hormone commonly associated with brooding behavior in female birds and lactation in mammals, provides a case in point. 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."

One does not need to be a father to experience these physical responses.

"In one preliminary study....a mere 15 minute of holding an infant could produce measurable increases in a man’s circulating levels of prolactin. 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."

Men’s nurturing responses can then, at least in some cases, be conditioned and enhanced. With all the social problems that arise from broken homes and deadbeat fathers, one has to wonder if society might not be in better shape if we encouraged teenage boys to earn extra money by babysitting, and conversely, pushed our young girls out to do some "bellowing, barking, or roaring."

Evolution has not provided men with the same socializing and nurturing instincts as women. Over the last 10-15,000 years human society has become more patriarchal and more conducive to the darker aspects of male behavior. The nurturing instincts of men may be lost entirely as they become even less associated with survival. Perhaps we can benefit by taking better advantage of the instincts that still exist. If the notion of babysitting teenage boys does not fly, Hrdy has another suggestion involving bottling the emanations of a newborn infant.

"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."

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