Chance Events Make Altruism Inevitable

Brewer's yeast has to cooperate to break down complex sugars, but it is only when it “works' with humans that it produces beer. Kzenon/Shutterstock

Random events help explain the old conundrum of why altruism is so common in nature, including among humans, a new study claims.

Under a crude interpretation of evolution, helping others makes no sense unless it benefits close relatives. Yet people risk their lives for strangers or even to rescue a puppy. The question of why troubles biologists and philosophers.

In Proceedings of the National Academy of Sciences, a team of researchers present a mathematical model that suggests chance events have programmed most of us towards pulling our weight.

The authors note that in most environments, there are “cooperators” who act to benefit others and “cheaters” who are only out for themselves. Despite the saying, cheats are expected to do better for themselves and thus pass on their genes. If cheating is hereditary, this should lead to more cheaters.

In the complex world of humans, where most people cooperate some of the time and cheat at others, this is hard to model, so the authors turned to Brewer's yeast for simplicity. Yeast produces the enzyme invertase, which breaks down complex sugars. A yeast that releases invertase gains a benefit, but non-producing yeasts gets to gobble up the simpler sugars, without expending the energy that goes into invertase production, an exemplar of cheating. Yet they have not taken over.

Dr Tim Rogers of the University of Bath said in a statement: "Scientists have been puzzled by this for a long time. One dominant theory was that we act more favorably towards genetic relatives than strangers, summed up by J. S. Haldane's famous claim that he would jump into a river to save two brothers or eight cousins.” Yet clearly this is not the whole answer. It is unlikely Haldane would have checked a family tree if he saw a child drowning, and certainly other species don't.

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