How politeness evolved
By Alan Boyle
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Taking turns isn't just a nice idea. It may be as much a part of the theory of evolution as survival of the fittest - at least that's the conclusion that British researchers reached after running a genetic simulation through thousands of generations of evolutionary change.
Turn-taking behavior seem to come naturally to humans, whether it's standing in line or deciding who's going to do the dishes tonight. But such behavior has been observed in a wide variety of other species as well: Chimps take turns grooming each other, for example, and penguins take turns minding their eggs.
"It is far from obvious how turn-taking evolved without language or insight in animals shaped by natural selection to pursue their individual self-interests," University of Leicester psychologist Andrew Colman said last week in a news release about the research.
Colman and a university colleague of his, Lindsay Browning, looked into the evolution of politeness for a paper published in the September issue of the journal Evolutionary Ecology Research - not by studying actual monkeys, penguins or line-standers, but by setting up a series of genetic simulations where they could dictate the rules of the evolutionary game.
The experiment was as much an exercise in game theory as in evolutionary biology. Colman and Browning programmed a computer to play a variety of games in which the payoff varied depending on whether the simulated players made the same or different choices.
One of the best-known games in this genre is the Prisoner's Dilemma, in which two prisoners receive different penalties depending on whether they defect or stay loyal to each other. Under the most common rules of the game, the most frequent outcome is for the prisoners to rat on each other, even though they would have been better off if they had both stayed loyal.
"The Prisoner's Dilemma, which is being used to study cooperation almost exclusively to date, doesn't ever give any advantage to automata that take turns," Colman told me. "In fact, it's created a blind spot in studying this issue, in our opinion."
He and Browning mixed up the repertoire by using six games, including the Prisoner's Dilemma as well as variations of cooperative games known as the Battle of the Sexes and Stag Hunt. They also built in a little mathematical mutation to duplicate what biologists have found happens in real life. Then they ran the simulation through 2,000 evolutionary generations. Each 2,000-generation simulation was repeated 10 times to check the stability of the results.
Here's how the experiment turned out: Under the right conditions, different players locked themselves into a pattern of mutually beneficial turn-taking that could sustain itself indefinitely.
"They didn't have the benefit of language to plan any strategy such as that," Colman said. "It could be something that just evolves through natural selection, just with hard wiring."
One factor was key, he said: "You've got to have two different types, because they've got to behave in different ways in the same situation in order to initiate this behavior. Without this genetic diversity, the behavior cannot evolve."
Even though game theorists may cast this diversity as a battle of the sexes (for example, she likes opera, he likes boxing), Colman emphasized that the diversity he had in mind was not necessarily a gender split, a la "Men Are From Mars, Women Are From Venus."
"I always tell my students, 'Women are from Earth, men are from Earth ... deal with it,'" he joked.
Rather, the diversity may take the form of different responses to environment changes (for example, becoming more dormant to conserve energy vs. becoming more active to seek out new food sources). Colman said turn-taking appears to be an instance of the "invisible hand" of natural selection at work.
"The assumption in the early days of evolutionary theory was that evolution would tend to make all organisms conform to an optimal form, and this would tend to reduce diversity. ... That turned out to be a primitive idea and not sufficiently subtle," he told me.
The fact that so many species exhibit turn-taking behavior suggests that the genetic code for cooperative behavior goes way back, Colman said. And that's a good thing, whether you're a yeast organism trying to metabolize sugar, an eel hunting for food in a coral reef ... or a filmgoer standing in line to see the latest "Harry Potter" movie.
"Humans obviously engage in turn-taking behavior. Queueing is an elaborate example of it," Colman said. "What this shows is that it's probably deep in our DNA. You don't have to necessarily assume that this is something that developed recently just because we're a civilized species."
Now it's your turn: Does this research shed new light on evolutionary theory? Is it merely a case of scientists stating the obvious? Or do you think "survival of the fittest" really doesn't explain turn-taking and other forms of altruistic behavior? Feel free to weigh in with your comments below.
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