A vervet monkey will scream an alarm when a predator is nearby, putting itself in danger.
A recent solution to the prisoner’s dilemma, a classic game theory scenario, has created new puzzles in evolutionary biology.Well, other than that what have you been up to?
When the manuscript crossed his desk, Joshua Plotkin, a theoretical biologist at the University of Pennsylvania, was immediately intrigued. The physicist Freeman Dyson and the computer scientist William Press, both highly accomplished in their fields, had found a new solution to a famous, decades-old game theory scenario called the prisoner’s dilemma, in which players must decide whether to cheat or cooperate with a partner. The prisoner’s dilemma has long been used to help explain how cooperation might endure in nature. After all, natural selection is ruled by the survival of the fittest, so one might expect that selfish strategies benefiting the individual would be most likely to persist. But careful study of the prisoner’s dilemma revealed that organisms could act entirely in their own self-interest and still create a cooperative community.
Press and Dyson’s new solution to the problem, however, threw that rosy perspective into question. It suggested the best strategies were selfish ones that led to extortion, not cooperation.
Plotkin found the duo’s math remarkable in its elegance. But the outcome troubled him. Nature includes numerous examples of cooperative behavior. For example, vampire bats donate some of their blood meal to community members that fail to find prey. Some species of birds and social insects routinely help raise another’s brood. Even bacteria can cooperate, sticking to each other so that some may survive poison. If extortion reigns, what drives these and other acts of selflessness?
Press and Dyson’s paper looked at a classic game theory scenario — a pair of players engaged in repeated confrontation. Plotkin wanted to know if generosity could be revived if the same math was applied to a situation that more closely resembled nature. So he recast their approach in a population, allowing individuals to play a series of games with every other member of their group. The outcome of his experiments, the most recent of which was published in December in the Proceedings of the National Academy of Sciences, suggests that generosity and selfishness walk a precarious line. In some cases, cooperation triumphs. But shift just one variable, and extortion takes over once again. “We now have a very general explanation for when cooperation is expected, or not expected, to evolve in populations,” said Plotkin, who conducted the research along with his colleague Alexander Stewart.
The work is entirely theoretical at this point. But the findings could potentially have broad-reaching implications, explaining phenomena ranging from cooperation among complex organisms to the evolution of multicellularity — a form of cooperation among individual cells.
Plotkin and others say that Press and Dyson’s work could provide a new framework for studying the evolution of cooperation using game theory, allowing researchers to tease out the parameters that permit cooperation to exist. “It has basically revived this field,” said Martin Nowak, a biologist and mathematician at Harvard University....MORE
