Contrary to our Darwinian inclinations, evolution may not be as dog-eat-dog of a world as we thought it was. The selfish can survive for a while, but according to new game theory research, long-term survival requires cooperation.
Game theorists were taken aback last year when a paper in the Proceeding of the National Academy of Sciences presented a new breakthrough strategy for the Prisoner’s Dilemma, a classic game theory situation that presents two prisoners with the opportunity to either cooperate or betray each other in exchange for lesser sentences, widely studied as a model for economics, psychology and evolutionary biology.
Using a strategy called zero-determinant, or ZD (meaning that in the mathematical model, the value called the determinant is set to zero), the paper argued that selfish players could be guaranteed to beat cooperative players, enforcing “a unilateral claim to an unfair share of rewards.” Since the Prisoner’s Dilemma is used to explain biological phenomena, it raised the question: Does evolution favor jerks?
Selfishness isn’t evolutionarily sustainable.Michigan State University microbiology and molecular genetics professor Christoph Adami and his research associate Arend Hintze immediately had doubts about whether ZD strategies could prove that evolution favors the selfish over the cooperative. In a paper published today in Nature Communications, they argue that according to their simulations, ZD strategies aren’t evolutionarily stable, and that eventually, selfish players would have to become cooperative to survive.
“We found evolution will punish you if you’re selfish and mean,” Adami said in a press statement, vindicating every 8-year-old with a schoolyard squabble.
“For a short time and against a specific set of opponents, some selfish organisms may come out ahead,” he explained. “But selfishness isn’t evolutionarily sustainable.”
That’s because the selfish strategy only works when ZD players compete against players that aren’t using the same strategy, and don’t know that they’re being manipulated. Against other ZD opponents, the strategy isn’t viable, and so eventually, when the pool of players narrows to only ZD strategists, they need to adapt other strategies to win. According to Adami, “in the long run they would have to evolve away from being ZD and become more cooperative. So they wouldn’t be ZD strategists anymore.”
I can’t do justice to the researchers’ complicated math here, but their methods are detailed in full in Nature Communications. (Open access!)