Cooperation has created a conundrum for generations of evolutionary scientists. If natural selection among individuals favors the survival of the fittest, why would one individual help another at a cost to itself? And yet cooperation and sacrifice are rampant in nature. Humans working together have transformed the planet to meet the needs of billions of people. Countless examples of cooperation between species exist as well. In this month's Origins essay, I examine our current understanding of this conundrum.
Cooperation has played a key role in evolutionary transitions, helping to create integrated systems. Worker ants have no offspring of their own and feed their queen’s offspring instead in colonies often considered “superorganisms” many thousands of individuals strong. Cells managed to specialize and stay together, giving rise to multicellular organisms. In both cases, formerly independent reproductive units become integrated into a single reproductive unit that became the target of selection.
The challenge of cooperation is to explain how self-interest is overcome, given the way natural selection works. Darwin suggested that selection might favor families whose members were cooperative, and researchers today agree that kinship helps explain cooperation. But cheaters—those who benefit without making sacrifices—are likely to evolve because they will have an edge over individuals that spend energy on helping others, thus threatening the stability of any cooperative venture. That puzzle has inspired biologists, mathematicians, even economists to come up with ways to explain how cooperation can arise and thrive. The essay examines how researchers have spent countless hours observing social organisms ranging from man to microbes. Humans are a particularly interesting case, as they cooperate with strangers, forgoing the genetic benefit derived from helping relatives. Yet even single-cell organisms have sophisticated means of working together. The study of both is helping to clarify the origin of this particularly important behavior.
Illustration credit: Katharine Sutliff/Science