If Trivers is right, then true altruism is what evolutionary biologists call a "maladaptation". Evolved to respond in a certain way to a given situation, we find it hard to act differently in the changed circumstances of the modern world. That would make strong reciprocity just another in a long list of maladaptations found in modern human behaviour, according to anthropologist John Tooby of the University of California at Santa Barbara. To make his point he gives the example of sexual desire, which most biologists agree evolved to spur the conception of offspring. Today, however, individuals experience sexual desire in many situations in which procreation is clearly impossible, "even when they know the object of their desire is imaginary, or a piece of paper", as Tooby says.
“Any organism that helps others at its own expense stands at an evolutionary disadvantage”Undoubt edly adaptations that evolved to help us cope under specific conditions can backfire when situations change. But not everyone is convinced by the idea that true altruism is such a maladaptation. Henrich disagrees with the theory's central premise. He believes that while our ancestors lived in small, close-knit groups, one-shot interactions with strangers would have been common even then. What's more, these interactions could have been crucial to people's survival, because they would have occurred over shared resources such as water holes and prey animals and, more crucially, in times of catastrophe such as flood or drought. "Environmental shocks would have guaranteed that strangers encountered one another during fitness-critical times," Henrich says.
If both one-shot and repeated interactions were routine in ancestral life, Henrich argues, evolution would presumably have prepared us to distinguish between the two with some precision. And that does seem to be the case. Two years ago economists Simon Gächter of the University of St Gallen in Switzerland and Armin Falk of the University of Bonn, Germany, looked at how people alter the way they play the prisoner's dilemma game depending on whether the game involves one-shot or repeated encounters with others. If people treat one-shot encounters as if they were repeated - as the maladaptation idea suggests - then there shouldn't be a difference. But they found that repeated play more than doubled cooperation levels, indicating that we are fully capable of adapting our behaviour to the situation at hand (The Scandinavian Journal of Economics, vol 104, p 1).
Further support for the idea that strong reciprocity is an adaptation in its own right comes from the theoretical studies of economist Herbert Gintis of the University of Massachusetts, Amherst, anthropologist Robert Boyd of the University of California at Los Angeles, and others. They set up a computer model in which groups of individuals interacted, and watched how their behaviour evolved. Individuals were set up in the model to behave initially either as cheats or as cooperators, and in personal interactions the former came off best. When groups competed with one another, however, cooperation came into its own: groups with more cooperators were likely to flourish.
But that was only the start. The individuals, whether initially cooperators or cheats, were also programmed to copy successful behaviour. In simulations with groups ranging from 4 to 256 individuals, the team found that altruism could evolve. The benefits that cooperation conferred on a group outweighed its costs to individuals - but only in groups of less than about 10. Ancestral human hunter-gatherer bands are thought to have numbered 30 or more individuals, so how could cooperative behaviour have evolved and spread in these groups?
The answer lies in the fact that strong reciprocity is not simply a matter of cooperation; it also requires punishment of those who fail to toe the line. When the team added punishment to their models, they found it made a huge difference. In a second round of simulations, they included a new kind of individual: the "punishers". These punishers were not only willing to cooperate with others but also to punish cheats. By making cheats pay for their antisocial actions, they tipped the balance towards cooperation. This time, competition between groups led to the emergence of cooperation in groups of up to 50 individuals (Proceedings of the National Academy of Sciences, vol 100, p 3531).
Could competition between small groups of our ancestors somehow have turned them into strong reciprocators? Gintis, Boyd and their colleagues believe so. What's more, subsequent research by Fehr, working with economist Urs Fischbacher of the University of Zurich, suggests that as humans came to live in larger groups, their attitudes towards reciprocity may have become even more hard-line. Using a similar model to Gintis and the others (Nature, vol 425, p 785), they found that cooperation can become the default behaviour in large groups provided punishers are willing to punish not only those who cheat, but also those who fail to punish cheats (see Graph). "In this case," Fehr says, "even groups of several hundred individuals can establish cooperation rates of between 70 and 80 per cent."
These findings suggest that true altruism, far from being a maladaptation, may be the key to our species' success by providing the social glue that allowed our ancestors to form strong, resilient groups. It is still crucial for social cohesion in today's very different world. "Something like it had to evolve," Gintis says.
In the absence of further discoveries, it seems likely that the argument over adaptation and maladaptation will continue. But this controversy is not the most important issue, says anthropologist Laurent Keller of the University in Lausanne, Switzerland. "Working out how humans behave is more interesting than whether it is adaptive or not."
Either way, there appears to be something deep within us that drives us to help others - even strangers. And if any of this suggests ways that fund-raisers might appeal to our altruistic tendencies when faced with the next humanitarian crisis, surely that is all to the good.
http://www.newscientist.com/article....mg18524901.600