How ant (and human) societies might grow

Pellegrino University Professor Emeritus Edward O. Wilson remains fascinated with the highly organized societies of ants, bees, wasps, termites, and humans. He and Bert Holldobler, with whom he shared a Pulitzer Prize for their book “The Ants,” have published a paper about how such societies originate, which appears in the Sept. 20, 2005 issue of Proceedings of the National Academy of Sciences. The original colonies of humans, like those of ants and termites, they propose, could have arisen in much the same way.

Both ants and humans have achieved “spectacular ecological success,” they write. For humans, this includes winning out over competing forms of humanlike creatures who evolved from apelike ancestors. Ant-type societies may be a common reason for such success.

The standard theory of the rise of eusocieties, as these evolutionarily advanced colonies are known, credits altruism, behavior that benefits others at the cost of the individual. For an ant, that would mean giving up the privilege of reproduction to become a sterile worker or soldier in the colony. For a human, it might mean fighting a war in a foreign land.

In this model, kinship is key. An individual insect gives up its fitness to foster that of the kin group. The colony is built on close genetic relationships with a push from an environment in which food, water, and shelter are plentiful.

Wilson says that he “once promoted this theory, although evidence for it is sparse. In the last two decades, however, much new and more solid evidence has turned everything upside down.” He and Holldobler now believe eusocial colonies can grow and prosper without such kinships. In fact, biological nepotism could be disruptive, they say.

Either way, any colony has to start with genes. These starter genes would be flexible, that is, include versions that aid altruism and thus promote cooperation. When such “social genes” are favored by natural selection, that helps their owners adapt to the environment and prosper.

“Eusociality can originate when founding members of the primitive colonies have low relatedness,” Wilson says. What counts is the social genes, not who is related to whom.

Wilson and Holldobler cite the example of a species of carpenter bee that has reached an early stage of eusociality. These insects form pairs, which then divide into queen and worker roles. Workers or subordinates usually stay if unrelated to a queen, but leave if they are related. Kinship, in this case, serves to weaken, rather than strengthen the colony.

Eventually, eusocial evolution pushes the colony beyond the point of no return. At this level, individual workers living in groups of ants, bees, and wasps no longer show a preference for their mothers in colonies with many queens. Nest-mates share food, groom each other, and recognize their fellows by scent. A chemical communication system arises that is comparable with the audiovisual system of humans.

“Colonies with lower relatedness among the workers often have higher growth and reproduction rates than those with higher relatedness,” Wilson notes. “This effect may be due to improved genetic resistance to disease or to the enhancement of division of labor by genetic proneness to specialization,” but not to kinship relations.