Human cooperation from violence?

If you think that we live in a more violent world than our predecessors, you would be agreeing with almost 300 people recently surveyed by the psychologist and writer, Steven Pinker. You would also be wrong. At a talk in the Harvard Law School, Pinker presented convincing evidence for a secular decline in violence across millennia, centuries, decades, and even years. He then attempted to answer two questions: why don't most people perceive that violence has declined, and why has it declined?

An earlier version of Pinker's ideas on violence can be found in one of his articles. Most of the talk is in it: http://www.edge.org/documents/archive/edge206.html#pinker He is now planning a book on the subject, with the potential title "The Better Angels of Our Nature".

Pinker presented three broad explanations for the secular decline in violence. Firstly, that Hobbes was quite right about life being "nasty, brutish and short", and that modern centralised states with a monopoly on violence function as Leviathan. Secondly, that technological advances have increased the number of positive-sum games, also known as win-win situations. Trade, for instance. Thirdly, that increasing ways to spread empathy, via fiction or journalism, for example, have helped to create the philosopher Peter Singer's "expanding circle". Humans are less violent now because more and more people (and sometimes animals) are included in an "in group" they can identify with.

The next day, Sarah Blafer Hrdy, renowned feminist sociobiologist, gave an equally synthetic talk on her latest book, Mothers and Others, that elaborates on the latter two of Pinker's explanations for declining human violence. Unlike Pinker, who is focusing largely on modern humans, and asking why we are so much more peaceful than ever before, Hrdy is interested in the evolutionary origins of human cooperative tendencies that far exceed those in other living apes.

I won't go into all the evidence that Hrdy presented in her talk, and in her book, but will outline her main ideas. At the moment, and ever since Darwin's Descent of Man in 1971, the predominant explanation for human cooperation is between-group conflict. The notion that our ancestors evolved to work together so they could defeat neighbouring tribes or families is apparently almost dogma amongst anthropologists.

In contrast, Hrdy contends that inter-group competition is not a sufficient, and probably not even the predominant force selecting for cooperative tendencies. Instead, she proposes that humans, unlike other apes, became extra good at sharing and reading each others minds and emotions because of communal child care. This probably sounds rather unconvincing when stated like that, but there are good arguments for taking Hrdy seriously.

All living great apes have rudiments of empathy and what philosophers like to call "theory of mind"-- kinowing that others can have thoughts different from your own. Humans, by the age of two, far outstrip captive-reared great apes in these mental abilities necessary for cooperation. Since great apes have rudiments of these abilities, we can assume that early humans did too. The question is, what caused strong selection in favour of increasing these abilities?

Cooperative breeding, a situation where some individuals forgo reproduction to help others rear offspring, has evolved independently in several species of insects, birds and mammals, and many times within primates alone. In other words, it's not hard to evolve into a cooperative breeder. Cooperative breeding also tends to evolve when the environment is harsh or unpredictable. The Pleistocene environment our ancestors lived in certainly was unpredictable, and Hrdy proposes that the lineage leading to humans evolved cooperative breeding.

Now we have some neural and genetic hardware for cooperative traits, and a novel communal rearing environment. As a result of being reared by multiple individuals instead of just Mum, offspring would develop mental abilities that had only existed as genetic potentials in the past. Natural selection cannot favour traits that are coded in DNA but aren't expressed in an individual's behaviour. So by exposing variation in capacities for empathy, cooperative breeding made it possible to also select for expanding these capacities, because the youngsters best able to persuade others to care for them, would be most likely to survive and pass on their abilities to engage with others.

One of the lovely things about this model, is that it provides a clear example of how intertwined "nature" and "nurture" are in evolution. Without some genetic capacity for empathy and social engagement, there would be no way for a novel rearing environment to extend the expression of such traits, and no way for the information to be passed to subsequent generations. Without the novel rearing environment, there would be nothing to select on or for genetic variation in the capacity to feel empathy.

Although Singer, Pinker and Hrdy have argued strongly for empathy being crucial for being nice to others, one could also point out that it is jolly useful in competitive contexts too. What better way to manipulate and deceive others for your own ends than to be able to read their minds and feelings? While humans, honeybees and meerkats are superb examples of cooperative breeding, conflict does occur within groups. Like most new technologies, cognitive tools such as theory of mind or empathy arguably extend our abilities to be both more cooperative and more competitive.