In his new book, The Social Conquest of Earth, E.O. Wilson explains his theory of everything—how hominids evolved, why war is common, how social insects became social, and why ants and bees and humans are so successful. Science writer Carl Zimmer spoke with Wilson.
When you use the phrase “the social conquest of earth” in the title of your book, what do you mean by that? How have social animals conquered the earth?
The most advanced social insects—ants, termites, many species of bees and wasp—make up only about 3 percent of the known species of animals on earth. But on the land they make up in most habitats upwards of 50 percent of the biomass. And of course humans, one of the very few of the largest animals that have reached the social level, has dominated in every respect.
And you see their social behavior as being key to these two kinds of animals having become so dominant?
When you study social insects, as I have, you see directly why eusocial, advanced social issues overall dominate because they will organize groups of individuals in seizing territory, in appropriating food, in defending their nest and generally controlling the parts of the environment for which they’re specialized.
How do you see the process by which you go from asocial species where insects are living as individuals to these incredibly highly organized societies? What do you see as being the progression through natural selection?
It’s actually fairly clear-cut when you take into account what we know about the evolutionary steps leading from completely solitary to eusocial or advanced social behavior. A great many solitary species—let’s say bees, wasps, the primitive cockroach—in the first stage build a nest and care for the young.
In the next stage, the mother or the mated pair stays with the nest and rears the young, defending them and securing food for them. In the next stage, whereas ordinarily the young would disperse upon reaching maturity, now they remain with the mother or the parents. And if that happens, and they work together as a group, then you have the advanced stage of social behavior.
A lot of scientists see social behavior as being partly the product of what’s called “inclusive fitness,” the effect that genes have not just in terms of an individual animal’s number of offspring but how many offspring their relatives may have. You’ve argued that inclusive fitness is not necessary and that you can focus on natural selection on individuals and on what you call “group selection” to explain how these social animals, like the social insects or humans, evolve their behavior. What do you mean when you use the term group selection?
As you might know, group selection became almost taboo in discussions on social behavior. But it comes back forcefully in the new theory developing about the origin of advanced social behavior.
The way I define it, group selection operates on the fitness, or lack thereof, of the social interactions in the group. In other words, it’s not simply group versus group in that sense but what actions individuals take that affect the group. And that would of course be communication, division of labor and the ability to read others’ intentions, which leads to cooperation.
When it’s an advantage to communicate or cooperate, those genes that promote it are going to be favored in that group if the group is competing with other groups. It gives them superiority over other groups and the selection proceeds at the group level, even as it continues to proceed at the individual level.
Are you envisioning groups fighting with each other or chasing each other off of good territory?
All of the above. It’s one of the most powerful forces still today and can range all the way from aggressive, extirpative warfare to control of neighbors’ territories through the advantage of a controlling group. Or it can simply include superior technology that allows a group to use land more effectively so that it can create larger populations and spread that way.
I think the key to understanding why advanced social behavior has been so rare, even though it’s highly successful when it happens, is that going from that first step over the threshold is difficult. It has to go through a period in which group selection is powerful enough to overcome this residual, individual level of selection, which is the main form of selection that’s been going on for countless numbers of generations before. Within groups, selfish individuals win and between groups, altruistic groups beat groups of selfish individuals.