Wednesday, November 12, 2014

Evolution and the “Sharing Gene”

Sociobiology is the name given to the attempt to associate observed social traits in humans with genetically acquired traits favored by natural selection.  Attempts to describe human social characteristics within this framework have been controversial, mainly because it is difficult to separate behaviors that might have been learned through social interaction from those that might be innate.  It is also difficult to explain how social characteristics might have become genetically embedded by natural selection.  While the behavior of an individual can certainly be affected by genetic dispositions, these can be characterized as a form of genetic noise leading to individual variation within the population, not a species-wide tendency.  Those who take positions on the issue seem to be driven as much by philosophy as by science.

One of the difficulties faced by sociobiologists is the need to explain the observed altruistic behavior in humans.  People do cooperate even when the benefits of cooperation are unevenly distributed and it might not be in their immediate self-interest.  People have been observed to sacrifice even their lives to protect the lives of others.  How does one explain this type of behavior using natural selection?

The simplest Darwinian approach to evolution is based on the presumed desire for individual organisms to strive to insure that their genes are propagated forward into the gene pool.  This is the “survival of the fittest” prescription.  The fittest is the one who produces the most offspring that make it into the next generation.  The mechanism of natural selection should then deselect any genetically-driven behavior in an individual organism that diminishes its opportunity to procreate and propagate its genes.  Such a trait should then disappear.  What is left is an arena in which individuals compete with each other to breed, to eat, and to control territory.

The situation becomes more complex when animals form kinship relationships and begin living in bands.  All sorts of social constraints and other behaviors become operative, and they vary considerably from species to species.  People seem to have little trouble believing that animal behavior is genetically based, but tend to resist the notion that human interactions are so constructed.

Humans live in groups that impose constraints on individual actions, and they have kin relationships that also impose constraints.  However, from tribe to tribe and society to society, these social rules can vary dramatically.  Consequently, the specific constraints cannot be genetic in nature; it must be the general willingness to live under a set of rules in order to enhance the survival of the band, tribe, or nation that might be genetic.  If this is correct, then how exactly did natural selection propagate this characteristic?

Edward O. Wilson is the scientist most closely associated with sociobiology.  In his book TheSocial Conquest of Earth, he postulates that human evolution was dominated by the need for bands of humans to compete with one another for resources.  This is an extension of the “survival of the fittest” theme.

“Our bloody nature, it can now be argued in the context of modern biology, is ingrained because group-versus-group was a principle driving force that made us what we are.  In prehistory, group selection lifted the hominids that became territorial carnivores to heights of solidarity, to genius, to enterprise.  And to fear.  Each tribe knew with justification that if it was not armed and ready, its very existence was imperiled.  Throughout history, the escalation of a large part of technology has had combat as its central purpose.”

“It should not be thought that war, often accompanied by genocide, is a cultural artifact of a few societies.  Nor has it been an aberration of history, a result of the growing pains of our species’ maturation.  Wars and genocide have been universal and eternal, respecting no particular time or culture.”

The groups that survive this competition are presumably those with the strongest social traits—those that allow its members to cooperate in battle even though some can expect to suffer more than others.  Some advantage of group membership must compete with an individual’s innate tendency to act selfishly to enhance its own survival.  Wilson sees this conflict between individual and group benefits as an inevitable characteristic of human societies.

“An unavoidable and perpetual war exists between honor, virtue, and duty, the products of group selection, on one side, and selfishness, cowardice, and hypocrisy, the products of individual selection on the other.”

However, genetic traits that support group collaboration within individuals must somehow get distributed to the group if group-beneficial behavior is to dominate.  Or, the genetic content of the group as a whole must be selected by superior procreative performance versus less effective groups.  Wilson refers to something called “multilevel selection.”  The process by which this occurs is a bit murky.

“Multilevel selection consists of the interaction between forces of selection that target traits of individual members and other forces of selection that target traits of the group as a whole.  The new theory is meant to replace the traditional theory based on pedigree kinship or some comparable measure of genetic relatedness.”

  Wilson’s concept of human evolution being dominated by “universal and eternal” warfare was discussed in AreHumans Inherently Warlike? and found wanting.  The supposition that humanity’s characteristics were honed in group competition in the context of “universal and eternal” warfare may find some support in the brief moment that is recorded history, but what about the previous million years or so.  In order to seek a genetic basis for subsequent evolution, one should look earlier in time to ascertain the reasons why people felt compelled to form groups in the first place.

What characterizes humans, and differentiates them from the other apes, is the development of social skills.  Chimpanzees are quite capable of conducting warfare with another band of chimps.  In fact, when human soldiers want to conduct an operation silently they use hand signals that would easily be understood by a chimp.  So why would warfare be a means of selecting the development of complex social skills?

Wilson provides his thoughts on the life of the early hunter-gatherer.

“Throughout their evolutionary past, during hundreds of thousands of years, they had been hunter-gatherers.  They lived in small bands, similar to present-day surviving bands composed of at least thirty and no more than a hundred or so individuals.  These groups were sparsely distributed.”

“Between 130,000 and 90,000 years ago, a period of aridity gripped tropical Africa far more extreme than any that had been experienced for tens of millennia previously.  The result was the forced retreat of early humanity to a much smaller range and its fall to a perilously low level in population….The size of the total Homo sapiens population on the African continent descended into the thousands and for a long while the future conqueror species risked complete extinction.”

Early humans faced periods when resources were so scarce that they faced near extinction.  Is this a situation in which one might expect starving people to go looking for someone to fight with?  Might they not have more wisely looked for someone who would be able to help them?

Early hunter-gatherers lived from hand-to-mouth.  They didn’t have stockpiles of food that someone would try to steal.  They were also subject to extreme variations in the success of their hunting and gathering.  If a band was, on the average, finding just enough food to survive, then some individuals would have gathered less than necessary for survival, and some would have gathered more than necessary.  If they had not learned to share food, eventually each individual would have an extended period of lean foraging, starve, and the band would disappear.

Sarah Blaffer Hrdy describes a study performed by observing the history of a present-day band of hunter-gatherers in her book Mothersand Others: The Evolutionary Origins of Mutual Understanding.  It illustrates how even in relatively benign times sharing within a band was necessary.

“The sporadic success and frequent failures of big-game hunters is a chronic challenge for hungry families among traditional hunter-gatherers.  One particularly detailed case study of South American forgers suggests that roughly 27 percent of a time a family would fall short of the 1,000 calories of food per person per day needed to maintain body weight.  With sharing, however, a person can take advantage of someone else’s good fortune to tide him through lean times.  Without it, perpetually hungry people would fall below the minimum number of calories they needed.  The researchers calculated that once every 17 years, caloric deficits for nonsharers would fall below 50 percent of what was needed 21 days in a row, a recipe for starvation.  By pooling their risk, the proportion of days that people suffered from such caloric shortfalls fell from 27 percent to only 3 percent.”

What is the purpose of living in a band if not to benefit from cooperation with other members?

The sharing of food is only one example of a benefit.  Hrdy believes that one of the great advances made by humans occurred when women learned to share the responsibility for raising children.  That allowed an individual mother more time to gather food and allowed her to give birth more frequently.  This and other cooperative activities could only exist if humans developed the ability to interpret, understand, and empathize with the feelings and intentions of others.

Hrdy believes this capability to share and cooperate has become hard-wired within us.

“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.”

Evolution and survival of the fittest need not be viewed as a competition to reward the strongest; it can also be considered as a means of selecting those most effective at cooperating.  Robert Trivers formulated an explanation for how repeated acts of altruism (or cooperation/sharing) could lead to natural selection of the tendency to perform those acts.  The key is to realize that even the earliest of humans realized that self-interest should be a long-term issue not one of immediate gratification

“In a 1971 paper Robert Trivers demonstrated how reciprocal altruism can evolve between unrelated individuals, even between individuals of entirely different species…. As Trivers says, it ‘take[s] the altruism out of altruism.’ The Randian premise that self-interest is paramount is largely unchallenged, but turned on its head by recognition of a broader, more profound view of what constitutes self-interest.”

One can follow Wilson and view humans as having been driven to their current state by “universal and eternal” warfare.

Or, one can view humans as having arrived at their current state via “universal and eternal” cooperation and sharing.

I know which view I prefer.

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