How Evolution Explains Altruism
By OREN HARMAN
Published: April 8, 2011
What do colon cancer, ant colonies, language and global warming have in common? This might sound like the front end of a joke, but in fact it’s a serious challenge to the standard view of evolution. Martin A. Nowak, the director of the Program for Evolutionary Dynamics at Harvard, has devoted a brilliant career to showing that Darwin, and particularly his followers, batted only two for three. Random mutation and natural selection have indeed been powerful motors for change in the natural world — the struggle for existence pitting the fit against the fitter in a hullabaloo of rivalry. But most of the great innovations of life on earth, Nowak argues, from genes to cells to societies, have been due to a third motor, and “master architect,” of evolution: cooperation.
Illustration by Lutz Widmaier
Altruism, Evolution, and Why We Need Each Other to Succeed
By Martin A. Nowak with Roger Highfield
330 pp. Free Press. $27
Excerpt: ‘SuperCooperators’ (Google Books)
“SuperCooperators” (written with Roger Highfield, editor of New Scientist magazine) is an absorbing, accessible book about the power of mathematics. Unlike Darwin with his brine bottles and pigeon coops, Nowak aims to tackle the mysteries of nature with paper, pencil and computer. By looking at phenomena as diverse as H.I.V. infection and English irregular verbs, he has formally defined five distinct mechanisms that have helped give rise to cooperative behavior, from the first molecules that joined to self-replicate, to the first cells that formed multicellular organisms, all the way to human societies, which exhibit a degree of cooperation unmatched in all creation. In Nowak’s view, figuring out how cooperation comes about and breaks down, as well as actively pursuing the “snuggle for existence,” is the key to our survival as a species.
At the heart of Nowak’s ideas is the haunting game of Prisoner’s Dilemma. The game involves two accomplices who are caught for a crime, interrogated separately and offered a deal. If one player incriminates the other, or “defects,” while the second remains silent, or “cooperates,” he will be given a sentence of one year, while the other player gets four. If both remain silent, they will be sentenced to only two years, but if both defect, they will receive three years. The rational choice for either prisoner is to defect, getting three years — though had both cooperated, they’d have been out in two. In the absence of trust, reason can be self-destructive.
In the 1990s, Nowak and Karl Sigmund, building on work by Robert Axelrod, showed that the Prisoner’s Dilemma, played over and over, could describe cycles of behavior in which strategies of selfishness (“Always Defect”) are beaten out by cooperation (“Tit for Tat”), then overtaken by even more cooperative behavior (“Generous Tit for Tat,” summarized as “Never forget a good turn, but occasionally forgive a bad one”), only to be invaded once more by egoists until the cycle begins anew. These “evolutionary dynamic” models, made more realistic by introducing an element of randomness, demonstrate that under the right conditions, competition can lead to teamwork. They also show how fragile that balance can be.
In “SuperCooperators,” Nowak argues that two of his mechanisms, indirect reciprocity and group selection, played an important role in human evolution. Think of a proto-simian trying to figure out whether to trust another in an exchange: Should I provide sex now for food and protection later? The proto-simian may have observed the behavior of its prospective partner, or it may not have; chances are good that others have, though. Reputation becomes important. The proto-simian evolves into a hominid, with a bigger brain allowing for more precise communication about reputation. Moral instincts evolve to produce shame, guilt, trust, empathy; social intelligence and conscience are born. Before you know it, Yogi Berra is summing it all up: “Always go to other people’s funerals, otherwise they won’t come to yours.” Language, cognition and morality, Nowak argues, are evolutionary spinoffs of the fundamental need of social creatures to cooperate.
Cooperation also breeds division of labor, as any ant or gene will tell you. When group size and structure, benefits and costs, all align just right, Nowak’s models show, the red talons of nature turn green. Sixty million years of fungus gardening by leaf cutter ants is one example, genes stacked on chromosomes another.
Nowak is one of the most exciting modelers working in the field of mathematical biology today. But a model, of course, is only as good as its assumptions, and biology is much messier than physics or chemistry. Nowak tells a joke about a man who approaches a shepherd and asks, “If I tell you how many sheep you have, can I have one?” The shepherd agrees and is astonished when the stranger answers, “Eighty-three.” As he turns to leave, the shepherd retorts: “If I guess your profession, can I have the animal back?” The stranger agrees. “You must be a mathematical biologist.” How did he know? “Because you picked up my dog.”
Nowak does his best to avoid dogs, but “SuperCooperators” gives little sense of the debates that have raged for years between two traditions of modeling evolution. One school considers the intricate complications of genetics, like the ways different versions of a gene interact in sexual reproduction. The other treats organisms as if they have a single set of chromosomes and reproduce asexually. At the heart of the debate lies the crucial question of whether natural selection is always maximizing the spread of an organism’s genes. Nowak belongs to the camp that assumes it is.
Nowak has also ignited controversy with a paper in the journal Nature, written with E. O. Wilson and Corina Tarnita, arguing that “inclusive fitness” — the idea that organisms cooperate with relatives because it helps pass on shared genes — is not necessary to explain the birth of complex societies like bees and ants, or altruism towards kin in humans. Nature recently published five critical letters, including one with 137 signatories, one of whom denounced the paper’s mathematics as not worth “wasting time” over.
Nowak gives little hint of these fierce debates in this cheerful book, instead offering this striking claim: “The way that we human beings collaborate is as clearly described by mathematics as the descent of the apple that once fell in Newton’s garden.” It seems significant to Nowak that, according to his models, the interest of groups can override the interests of individuals if “the ratio of the benefits to cost is greater than one plus the ratio of group size to number of groups,” and that cooperation can prevail if altruists cluster together in particular topographies. If only we could take such facts into account, as special cancer-preventing “crypt” formations in our colons have unthinkingly done, perhaps we might work together to combat global warming.
Near the end of the book, Nowak describes Gustav Mahler’s efforts, in his grandiloquent Third Symphony, to create an all-encompassing structure in which “nature in its totality may ring and resound,” adding, “In my own way, I would like to think I have helped to give nature her voice too.” But there remains a telling gap between the precision of the models and the generality of the advice Nowak offers for turning us all into supercooperators. We humans really are infinitely more complex than falling apples, metastasizing colons, even ant colonies. Idealized accounts of the world often need to ignore the messiness of reality. Mahler understood this. In 1896 he invited Bruno Walter to Lake Attersee to glimpse the score of the Third. As they walked beneath the mountains, Walter admonished Mahler to look at the vista, to which he replied, “No use staring up there — I’ve already composed it all away into my symphony!”