Edward O. Wilson of Harvard University knows the terrifying power of the nest firsthand—and first-ankle, crook of the knee, any patch of skin that happened to be unsheathed as the eminent evolutionary biologist has crept through tropical rainforests studying some of the most aggressive ant species in the world. Ants are a wildly successful sector of nature’s bestiary, accounting for maybe a quarter of all terrestrial animal matter—the same percentage of biomass that we humans can claim. They’re found on every continent save Antarctica and in just about every possible setting, and though you may dislike ants at a picnic, you’d dislike even more a park that was scrubbed antiseptically ant-free.

As Wilson has learned through painful experience, ants will defend their nest vigorously, violently, to the death if need be; and the more elaborate the dwelling, the more ferocious the homeland security system. In the forest canopies of equatorial Africa and Asia, weaver ants construct spectacular swaglike nests of leaves stitched together with silken threads extracted from the colony’s larval ranks. Should any creature venture within smelling distance of the nests, weaver ant soldiers will boil out to bite and spray bullets of formic acid. In the Solomon Islands during World War II, Wilson writes, “marine snipers climbing into trees were said to fear weaver ants as much as they did the Japanese.”

In his newly published The Social Conquest of the Earth—the 27th book from this two-time winner of the Pulitzer Prize—Wilson argues the nest is central to understanding the ecological dominance not only of ants, but of human beings, too. Ants rule the microhabitats they occupy, consigning other insects and small animals to life at the margins; humans own the macroworld, Wilson says, which we have transformed so radically and rapidly that we now qualify as a kind of geological force. How did we and the ants gain our superpowers? By being super-cooperators, groupies of the group, willing to set aside our small, selfish desires and I-minded drive to join forces and seize opportunity as a self-sacrificing, hive-minded tribe. There are plenty of social animals in the world, animals that benefit by living in groups of greater or lesser cohesiveness. Very few species, however, have made the leap from merely social to eusocial, “eu-” meaning true. To qualify as eusocial, in Wilson’s definition, animals must live in multigenerational communities, practice division of labor and behave altruistically, ready to sacrifice “at least some of their personal interests to that of the group.” It’s tough to be a eusocialist. Wouldn’t you rather just grab, gulp and go? Yet the payoffs of sustained cooperation can be huge. Eusociality, Wilson writes, “was one of the major innovations in the history of life,” comparable to the conquest of land by aquatic animals, or the invention of wings or flowers. Eusociality, he argues, “created super­organisms, the next level of biological complexity above that of organisms.” The spur to that exalted state, he says, was always a patch of prized real estate, a focal point luring group members back each day and pulling them closer together until finally they called it home. “All animal species that have achieved eusociality, without exception, at first built nests that they defended from enemies,” Wilson writes. An anthill. A beehive. A crackling campfire around which the cave kids could play, the cave elders stay and the buffalo strips blacken all day. Trespassers, of course, would be stoned on sight.

As Wilson sees it, human beings are eusocial apes, and in our brand of extreme togetherness we stand apart—from other living monkeys and apes, and from the many hominids that either preceded or coexisted with us and are now extinct, including Homo neanderthalensis, who apparently weren’t much for constructing elaborate campsites or other nest equivalents. Against the impetus of a Homo sapiens united front, forged at the campfire and undoubtedly amplified through the frequent singing of “100 bottles of mead on the wall,” the Neanderthals may well have been as helpless as grasshoppers in the path of army ants.

Yet our eusocial nature, Wilson emphasizes, is nothing like that of the robotic ants. It developed along an entirely different route and is bound up with other aspects of our humanity—our anatomy, our intellect and emotions, our sense of free will. He takes us on an elegant spin through our prehistory, highlighting the stepwise rules of engagement for achieving total global dominance. Rule No. 1: Be a terrestrial animal. “Progress in technology beyond knapped stones and wooden shafts requires fire,” Wilson says. “No porpoise or octopus, no matter how brilliant, can ever invent a billows and forge.” Rule No. 2: Be a large terrestrial animal. The vast majority of land creatures weigh barely a pound or two, but if you’re going to have a big brain, you need a large body to support it. No. 3: Get the hands right. Forget standard-issue paws, hooves or claws. To hold and manipulate objects, you need “grasping hands tipped with soft spatulate fingers.” With our flexible digits and opposable thumbs, we became consummate kinesthetes, sizing up the world manually and enriching our mind. “The integrative powers of the brain for the sensations that come from handling objects,” Wilson says, “spill out into all other domains of intelligence.” That goes for social intelligence in spatulate spades. With hands we can wave hello, seal a deal, keep in touch or join in a circle, unite the many as one.

Our hypersocial spirit is both a great blessing and a terrible curse. Experiments have shown that it is shockingly easy to elicit a sense of solidarity among a group of strangers. Just tell them they’ll be working together as a team, and they immediately start working together as a team, all the while attributing to each other a host of positive qualities like trustworthiness and competence—an instant five-star customer review.

Yet we are equally prepared to do battle against those who fall outside the fraternal frame. In experiments where psychologists divided people into groups of arbitrarily assigned traits—labeling one set the Blue team and another the Green, for example—the groups started sniping at each other and expressing strong prejudices toward their “opponents,” with the Greens insisting the Blues were untrustworthy and unfair. The “drive to form and take deep pleasure from in-group membership easily translates at a higher level into tribalism,” Wilson says, and can spark religious, ethnic and political conflicts of breathtaking brutality.

Wilson also traces what he considers the tragedy of the human condition to the private struggle of us versus me. He sees us as a kind of mixed economy, the complicated fruit of a sharply disputed process known as multilevel selection. By this reckoning, some of our impulses are the result of individual selection, the competition of you against everybody else for a share of life’s goodies. Other traits are under the sway of group selection, prompting us to behave altruistically for the sake of the team. It appears our individually selected traits are older and more primal, harder to constrain, the ones we traditionally label vices: greed, sloth and lust, the way we covet our neighbor’s life and paper over our failings with pride. Our eusocial inclinations are evolutionarily newer and more fragile and must be vociferously promoted by the group if the group is to survive. They are the stuff of religions and Ben Franklin homilies and represent the virtues we admire: to be generous, kind and levelheaded, to control our impulses, keep our promises and rise to the occasion even when we are scared or disheartened. “The human condition is an endemic turmoil rooted in the evolution processes that created us,” he writes. “The worst in our nature coexists with the best, and so it will ever be.”

Not all biologists agree with Wilson’s ideas about the source of humanity’s dominance or existential angst. Some resist calling humans eusocial, preferring to restrict that term to animals like ants, in which just one or a few group members reproduce and the rest attend to the royal ones’ brood. Other biologists dislike invoking group selection, saying simpler, time-tested models based on individual genealogies will do. Still others have adopted a remarkably sunny view of humanity and its prospects. The social scientist Steven Pinker, also of Harvard, argues in his recent book The Better Angels of Our Nature that war and violent conflict have been declining steadily and may soon be obsolete. Like Wilson, Pinker believes that evolutionary forces have shaped human nature into a complex amalgam of the bestial and heroic, the compassionate and pitiless (although in Pinker’s view, those forces do not include group selection). Yet Pinker argues that, even while we retain our base and bloody impulses, historical trends such as stronger governments, increased prosperity, literacy, education, trade and the empowerment of women have allowed us to effectively tame them.

For his part, Wilson cultivates a beautifully appointed gloom. “We have created a Star Wars civilization, with Stone Age emotions,” he says. “We thrash about” and are “a danger to ourselves and the rest of life.” Our conquest of earth has happened so quickly that the rest of the biosphere has not had time to adjust and our heedless destruction of species shows scant signs of abating.

Nevertheless, Wilson says, “Out of an ethic of simple decency to one another, the unrelenting application of reason, and acceptance of what we truly are,” we may yet turn earth into a “permanent paradise for human beings, or the strong beginnings of one.” We’re not ants, and we can do what ants can’t: pull up to the nearest campfire, toast a marshmallow, sing a song.