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Evolution punishes selfish jerks in long run, study finds

Aug. 1, 2013
Courtesy of Michigan State University
and World Science staff

Two bi­ol­o­gists have pub­lished ev­i­dence that ev­o­lu­tion does­n’t fa­vor the self­ish—dis­prov­ing, they claim, a the­o­ry pop­u­lar­ized last year.

“We found ev­o­lu­tion will pun­ish you if you’re self­ish and mean,” said Mich­i­gan State Uni­vers­ity bi­ol­o­gist Christoph Adami, lead au­thor of the new stu­dy, pub­lished in the Aug. 1 is­sue of Na­ture Com­mu­nica­t­ions.

“For a short time and against a spe­cif­ic set of op­po­nents, some self­ish or­gan­isms may come out ahead. But self­ishness is­n’t ev­o­lu­tion­arily sus­tain­able.”

Much of the last 30 years of re­search has fo­cused on how coop­era­t­ion evolved, since it’s found in many forms of life, from single-cell or­gan­isms to peo­ple. The the­o­ry of ev­o­lu­tion of­fers no ob­vi­ous an­swers as to why. Bi­ol­o­gists fol­low Charles Dar­win in sup­pos­ing that the best-adapted or­gan­isms in a giv­en en­vi­ron­ment will even­tu­ally win out and dom­i­nate the gene pool. But these “fittest” or­gan­isms by no means would seem to ob­vi­ously in­clude “nice guys” or coop­erators, who put them­selves at a dis­ad­vant­age in many re­spects.

One way to ad­dress the ques­tion is through game the­o­ry, a branch of ap­plied math­e­mat­ics used in bi­ol­o­gy, eco­nom­ics, po­lit­i­cal sci­ence and else­where. Game the­o­ry stud­ies win­ning strate­gies for par­ties in­volved in situa­t­ions where their in­ter­est con­flict. Com­put­er sim­ula­t­ions can be de­vised to as­sess the re­sults of dif­fer­ent strate­gies.

Adami and col­leagues used the “pris­on­er’s di­lem­ma game” as a com­put­er mod­el to study coop­era­t­ion. In the game, two peo­ple are ar­rested for a crime. Po­lice of­fer each per­son a deal: snitch on your friend and go free while the friend spends six months in jail. If both pris­on­ers snitch, they both get three months in jail. If they both stay si­lent, they both get one month in jail for a less­er of­fense. If the two pris­on­ers get a chance to talk to each oth­er, they can es­tab­lish trust and are usu­ally more likely to coop­erate be­cause then both of them only spend one month in jail. But if they’re not al­lowed to com­mu­ni­cate, the best strat­e­gy is to snitch be­cause it guar­an­tees the snitch­er does­n’t get the long­er jail term.

The game lets sci­en­tists study a bas­ic ques­tion com­peti­tors face: do I act self­ishly or do I coop­erate? Co­op­er­at­ing would do the most good for the most in­di­vid­u­als, but it might be tempt­ing to be self­ish and free­load, let­ting oth­ers do the work and take the risks.

Last year, two lead­ing phys­i­cists pub­lished a pa­per show­ing their newly dis­cov­ered strat­e­gy—called zero-determinant, or ZD—gave self­ish play­ers a guar­an­teed way to beat co­op­er­a­tive play­ers. This would pose new prob­lems for ex­plain­ing the ev­o­lu­tion of coop­era­t­ion. 

“The pa­per caused quite a stir,” said Adami. “The main re­sult ap­peared to be com­pletely new, de­spite 30 years of in­tense re­search in this area.” That pa­per was pub­lished in the June 26, 2012 is­sue of the jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

Adami and co-au­thor Arend Hintze, al­so of Mich­i­gan State, ques­tioned wheth­er fol­lowing the ZD strat­e­gy would es­sen­tially elim­i­nate coop­era­t­ion and cre­ate a world full of self­ish be­ings. They used high-pow­ered com­put­ing to run hun­dreds of thou­sands of games and found, they said, that ZD strate­gies can nev­er be the prod­uct of ev­o­lu­tion. 

While ZD strate­gies of­fer ad­van­tages when used against non-ZD op­po­nents, they don’t work well against oth­er ZD op­po­nents, they said.

“In an ev­o­lu­tion­ary set­ting, with popula­t­ions of strate­gies, you need ex­tra in­forma­t­ion to dis­tin­guish each oth­er,” Adami said. ZD strate­gies only worked if play­ers knew who their op­po­nents were and adapted their strate­gies ac­cord­ing­ly, he added.

“The only way ZD strate­gists could sur­vive would be if they could rec­og­nize their op­po­nents,” Hintze said. “And even if ZD strate­gists kept win­ning so that only ZD strate­gists were left, 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.”

The re­search al­so makes that case that com­mu­nica­t­ion and in­forma­t­ion are nec­es­sary for coop­era­t­ion to take place. “S­tan­dard game the­o­ry does­n’t take com­mu­nica­t­ion in­to ac­count be­cause it’s so com­pli­cat­ed to do the math for the ex­pected pay­offs,” Adami ex­plained. 

But “we think com­mu­nica­t­ion is the rea­son coop­era­t­ion oc­curs. It’s gen­er­ally be­lieved that there are five in­de­pend­ent mech­a­nisms that fos­ter coop­era­t­ion. But these mech­a­nisms are really just ways to en­sure that coop­erators play mostly with oth­er coop­erators and avoid all oth­ers. Com­mu­nica­t­ion is a uni­ver­sal way to achieve that. We plan to test the idea di­rectly in yeast cells.”


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Two biologists have published evidence that evolution doesn’t favor the selfish—disproving, they say, a theory popularized last year. “We found evolution will punish you if you’re selfish and mean,” said Michigan State University biologist Christoph Adami, lead author of the new study, published in the Aug. 1 issue of Nature Communications “For a short time and against a specific set of opponents, some selfish organisms may come out ahead. But selfishness isn’t evolutionarily sustainable.” Much of the last 30 years of research has focused on how cooperation evolved, since it’s found in many forms of life, from single-cell organisms to people. The theory of evolution offers no obvious answers as to why. Biologists follow Charles Darwin in supposing that the best-adapted organisms in a given environment will eventually win out and dominate the gene pool. But these “fittest” organisms by no means would seem to obviously include “nice guys” or cooperators, who put themselves at a disadvantage in many respects. One way to address the question is through game theory, a branch of applied mathematics used in biology, economics, political science and elsewhere. Game theory studies winning strategies for parties involved in situations where their interest conflict. Computer simulations can be devised to assess the results of different strategies. Adami and colleagues used the “prisoner’s dilemma game” as a computer model to study cooperation. In the game, two people are arrested for a crime. Police offer each person a deal: snitch on your friend and go free while the friend spends six months in jail. If both prisoners snitch, they both get three months in jail. If they both stay silent, they both get one month in jail for a lesser offense. If the two prisoners get a chance to talk to each other, they can establish trust and are usually more likely to cooperate because then both of them only spend one month in jail. But if they’re not allowed to communicate, the best strategy is to snitch because it guarantees the snitcher doesn’t get the longer jail term. The game lets scientists study a basic question competitors face: do I act selfishly or do I cooperate? Cooperating would do the most good for the most individuals, but it might be tempting to be selfish and freeload, letting others do the work and take the risks. Last year, two leading physicists published a paper showing their newly discovered strategy—called zero-determinant, or ZD—gave selfish players a guaranteed way to beat cooperative players. This would pose new problems for explaining the evolution of cooperation. “The paper caused quite a stir,” said Adami. “The main result appeared to be completely new, despite 30 years of intense research in this area.” That paper was published in the June 26, 2012 issue of the journal pnas. Adami and co-author Arend Hintze, also of Michigan State, questioned whether following the ZD strategy would essentially eliminate cooperation and create a world full of selfish beings. They used high-powered computing to run hundreds of thousands of games and found, they said, that ZD strategies can never be the product of evolution. While ZD strategies offer advantages when used against non-ZD opponents, they don’t work well against other ZD opponents, they said. “In an evolutionary setting, with populations of strategies, you need extra information to distinguish each other,” Adami said. ZD strategies only worked if players knew who their opponents were and adapted their strategies accordingly, he added. A ZD player would play one way against another ZD player and a different way against a cooperative player. “The only way ZD strategists could survive would be if they could recognize their opponents,” Hintze added. “And even if ZD strategists kept winning so that only ZD strategists were left, 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.” The research also makes that case that communication and information are necessary for cooperation to take place. “Standard game theory doesn’t take communication into account because it’s so complicated to do the math for the expected payoffs,” Adami explained. But “we think communication is the reason cooperation occurs. It’s generally believed that there are five independent mechanisms that foster cooperation. But these mechanisms are really just ways to ensure that cooperators play mostly with other cooperators and avoid all others. Communication is a universal way to achieve that. We plan to test the idea directly in yeast cells.”