Our species has more forms of social organization than the rest of the primate order combined

From The Secret of Our Success by Joseph Henrich. How culture is driving evolution. Page 10.

Other species have also spread widely and achieved immense ecological success; however, this success has generally occurred by speciation, as natural selection has adapted and specialized organisms to survive in different environments. Ants, for example, capture an equivalent biomass to modern humans, making them the most dominant of terrestrial invertebrates. To accomplish this, ant lineages have split, genetically adapted, and specialized into more than 14,000 different species with vast and complicated sets of genetic adaptations.5 Meanwhile, humans remain a single species and show relatively little genetic variation, especially when the diverse range of environments we inhabit is considered. We have, for example, much less genetic variation than chimpanzees and show no signs of splitting into subspecies. By contrast, chimpanzees remain confined to a narrow band of tropical African forest and have already diverged into three distinct subspecies. As will become clear in chapter 3, the manner in which we adapt to diverse environments, and why we thrive in so many different ecologies, does not arise from an array of environment-specific genetic adaptations, as with most species.

If not a dizzying array of genetic adaptations, what is the secret of our species’ success? Most would agree that it traces, at least in part, to our ability to manufacture locally appropriate tools, weapons, and shelters, as well as to control fire and harness diverse food sources, like honey, game, fruit, roots, and nuts. Many researchers also point to our cooperative abilities and diverse forms of social organization. Human hunter-gatherers all cooperate intensively within families and to some degree on larger scales ranging from a few families, called bands, to tribes of thousands. These forms of social organization vary on a bewildering array of dimensions, with differing dimensions, with differing rules for group membership/identity (e.g., tribal groups), marriage (e.g., cousin marriage, see chapter 9), exchange, sharing, ownership, and residence. Just considering hunter-gatherers, our species has more forms of social organization than the rest of the primate order combined.