Sunday, January 1, 2012

Of Chimps and Men: Mothers and Others

After an immersion in humanity’s recent history, with all its instances of violent aggression, one is tempted to look to our evolutionary history for some explanation for our behavior. 

Scientists tell us that Chimpanzees are our closest cousins, genetically, and that our human ancestors diverged from the chimpanzee line about six million years ago. The chimpanzees, themselves, bifurcated into two groups about one million years ago. These two groups were geographically separated and developed quite different social behaviors over the years. The most familiar and most prevalent is referred to as a common chimpanzee. The younger branch of the species is usually referred to as a bonobo. Both exhibit many human-like qualities.

An attempt to invoke a relationship between our violent behavior and that of chimpanzees was made in an article: Of Chimps and Men. This attempt failed in the face of the differences in response to strangers by common chimps and bonobos. If one million years of evolution can produce radical changes in social responses, then the six million years of independent evolution by humans should lead to behavior patterns that were unique to humans. If we are a violent species then we will have to look for the explanation in our separate development.

Sarah Blaffer Hrdy has written a fascinating book that delves into the issues of man’s evolution and how it differs from that of chimps and the other ape species. She provides a quite different perspective: in her book Mothers and Others.

Hrdy’s specialty is evolutionary anthropology, and she is a widely-respected researcher in that field. Her focus is not on the similarities between humans and other apes, but on the differences. She tells us that the secret of understanding the development of the human species lies not in our potential for aggressive behavior, but in our development of cooperative social behavior. By nature we are collaborators, not aggressors—or at least we were until recently.

Hrdy begins her story with an illuminating section titled Apes on a Plane. She reminds us that the human ape routinely endures trying circumstances on airplane flights where they are cramped together in small spaces with total strangers, crying infants, and obnoxious neighbors. This is usually a situation more characterized by cooperative, empathetic interactions than by violence.

"What if I were traveling with a planeload of chimpanzees? Any one of us would be lucky to disembark with all ten fingers and toes still attached, with the baby still breathing and unmaimed. Bloody earlobes and other appendages would litter the aisles. Compressing so many highly impulsive strangers into a tight space would be a recipe for mayhem."

According to Hrdy the most distinctive human attribute is the ability to interpret, understand, and empathize with the feelings and intentions of others.

"From a tender age and without special training, modern humans identify with the plights of others and without being asked, volunteer to help and share, even with strangers. In these respects, our line of apes is in a class by itself."

"This ability to identify with others and vicariously experience their suffering is not simply learned: It is a part of us."

Hrdy devotes her book to explaining how these attributes were required for human survival, and how natural selection made them part of our genetic makeup. Her theories are at odds with generations of assumptions about evolution driven by competition for resources, and with economic theories that celebrate the notion individualism and assume "rational" people who pursue their own interests.

"When considered in the context for how humankind managed to survive vast stretches of time and dramatic fluctuations in climate during the Pleistocene, in the period from around 1.8 million years ago until about 12,000 BCE, such generous tendencies turn out to be "better than rational" because people had to rely so much on time-tested relationships with others."

One can learn much about apes and other primates by studying them in captivity, where the environment is artificial, but it is best to study them in the wild where their habitat is consistent with that in which they evolved. There is a similar statement to be made about humans. In a sense we are all captives in our current environment, which is quite different from that in which we evolved. The closest thing we have to studying humans in the wild is to look at what is known about human hunter-gatherer societies, some of which still exist.

Hyrdy tells us that individual hunter-gatherers live in a feast or famine mode. If they had not learned to share and collaborate, mankind would never have survived. Their societies are often characterized by rituals of gift exchanges intended to form or strengthen social bonds. The greater is the number of potential collaborators, the greater the probability of survival. This makes sense as a learned response, but Hrdy must explain it as a genetically-wired response. She indicates the evolution of the infant-mother interaction as the key.

Apes possess the same mirror neurons that allow one to vicariously simulate the observed actions of others. Researchers identify these brain structures as the source of a great deal of our ability to transmit knowledge, emotion, and intent from one individual to another. In humans, these capabilities are much more developed than in the other apes. According to Hrdy, the reason why is derived from evaluating the treatment of infants.

Human infants are born with the urge to imitate and understand the emotions and intentions of those they encounter, an activity dominated by the bond with their mother. Similar tendencies have been observed in other ape species, but they tend to not be as strong and they tend to dissipate rapidly with time.

Consider the infant nonhuman ape and its interaction with its mother. In ape societies, infants are at continual risk. As long as the mother is suckling her infant, she is not available to a lusty male. Infanticide by male apes desiring to mate with the mother is the most common cause of infant death in some societies. The mother must also be concerned with predators, including jealous females who might choose to steal her baby. The result is that the mother never leaves her infant alone. They are in constant physical contact, a process that is aided by the hairy body of the mother and the grasping instinct of the infant. This instinct is so strong that mothers have been observed to cling to and attempt to nurture infants born so deformed that they have no chance for survival.

Hrdy claims that the human infant saw a much different situation. Human mothers have the same instincts as other apes, but they have demonstrated the tendency to calculate the probability that they will be able to support their infants, and are capable of allowing an infant to die if necessary. This calculation is generally based on the ability to procure support from kin or neighbors. A hunter-gatherer female would need to acquire food for herself and her infant. She could not do this and maintain physical contact with her infant. It was necessary to have others available to protect and nurture her baby while she gathered. It became a matter of survival that infants develop attributes that promoted rapid and strong bonds not only with their mothers, but with anyone they might come in contact with. It was necessary for human infants to learn to read the emotions and intentions of others in order that they encourage care and nurturing rather than neglect. Whereas the machinations made possible by mirror neurons tended to remain rudimentary in other apes because they were not necessary for survival, they continued to develop in humans because they were required for survival.

Anyone who has observed infants will be familiar with their interest in staring into peoples’ faces and trying to understand what they observe. Also familiar are the attempts to imitate the actions they observe around themselves. Soon they make conscious attempts to perform acts that they think will endear themselves to others, followed by anxious looks to see if their performance has been met with approval. Children are observed to willingly share their possessions with others. These are behaviors that are uniquely human among the ape species. Hrdy identifies these survival-driven abilities to interpret and understand the emotions and intentions of others, and to acquire the approval of others, as the bases for subsequent human development.

In order to not impugn the maternal instincts of human mothers, one needs a little context. Humans, as we exist now, are characterized mainly by large, efficient brains, ever so slow maturation, and exceptional language skills. There was a time when the female of the species was only about half the size of the male. If large-brained, slow-maturing infants were to be produced, the females would have to grow larger. This required the acquisition of much greater quantities of food, and created the need for the mother to spend much more of her time out gathering—a process hindered by having to carry around an infant at the same time. Thus developed the necessity for "cooperative breeding," and the need for "alloparents" to assist the mother in caring for her infant. These alloparents were, ideally, kin, mothers, siblings, neighbors—and the occasional father. This approach to caring for infants allowed women to give birth more frequently than the other major apes, increasing the chance of survival of the species and allowing the population to grow more rapidly.

In Hrdy’s scenario, we did not develop into creatures capable of great civilizations because our bigger brains allowed us to develop the necessary social skills, it was the development—starting over a million years ago—of social skills required for survival that made possible the evolution of the large-brained human.

Hrdy provides us with an interesting and compelling narrative. She finishes the tale by reminding us that the conditions that drove us to be sociable, cooperative animals are no longer operative. Over the last 10,000 years or so they have been replaced by an environment that does not demand the same behaviors on the part of mothers and infants. Evolution can work quickly to dilute characteristics that are no longer necessary for survival, and can produce unknowable consequences. Our violent behavior may have been encouraged more by quite recent developments rather than by ancient evolution.

There will be more on these issues later.

For those who are interested in this subject and do not wish to read the book, there is an additional review in The New York Review of Books by Melvin Konner: It Does Take a Village.

1 comment:

  1. Michaela (Czech republic)December 2, 2013 at 3:26 AM

    Thanks for this review, very helpful!

    ReplyDelete

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