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Many animals are social: they live in groups, flocks, or herds. But only a few animals have crossed the threshold and become ultrasocial, which means that they live in very large groups that have some internal structure, enabling them to reap the benefits of the division of labor.
One of the key features that has helped all the nonhuman ultra-socials to cross over appears to be the need to defend a shared nest.
to two other factors: the need to feed offspring over an extended period (which gives an advantage to species that can recruit siblings or males to help out Mom) and intergroup conflict.
“It is inconceivable that you would ever see two chimpanzees carrying a log together.”
Tomasello’s great innovation was to create a set of simple tasks that could be given to chimps and to human toddlers in nearly identical form.
But other tasks required collaborating with the experimenter, or at least recognizing that she intended to share information.
The kids aced these social challenges, solving them correctly 74 percent of the time. The chimps bombed, solving them just 35 percent of the time (no better than chance on many of the tasks).
human cognition veered away from that of other primates when our ancestors developed shared intentionality.
When everyone in a group began to share a common understanding of how things were supposed to be done, and then felt a flash of negativity when any individual violated those expectations, the first moral matrix was born.
Tomasello believes that human ultrasociality arose in two steps. The first was the ability to share intentions in groups of two or three people who were actively hunting or foraging together. (That was the Rubicon.)
more collaborative groups began to get larger, perhaps in response to the threat of other groups.
This was the second step: Natural selection favored increasing levels of what Tomasello calls “group-mindedness”—the ability to learn and conform to social norms, feel and share group-related emotions, and, ultimately, to create and obey social institutions, including religion.
Tomasello notes that a word is not a relationship between a sound and an object. It is an agreement among people who share a joint representation of the things in their world, and who share a set of conventions for communicating with each other about those things.
When culture accumulates, it means that people are learning from each other, adding their own innovations, and then passing their ideas on to later generations.
beginning around 2.4 million years ago, hominids with larger brains begin to appear in the fossil record. These were the first members of the genus Homo, including Homo habilis, so named because these creatures were “handy men” compared to their ancestors.
FIGURE 9.1. Time line of major events in human evolution. MYA = million years ago; KYA = thousand years ago. Dates drawn from Potts and Sloan 2010; Richerson and Boyd 2005; and Tattersall 2009.
beginning around 1.8 million years ago, some hominids in East Africa began making new and more finely crafted tools, known as the Acheulean tool kit.61
But here’s the weird thing: Acheulean tools are nearly identical everywhere, from Africa to Europe to Asia, for more than a million years.
the knowledge of how to make these tools may have become innate, just as the “knowledge” of how to build a dam is innate in beavers.
Homo heidelbergensis is therefore our best candidate for Rubicon crosser.
For example, one of the best-understood cases of gene-culture coevolution occurred among the first people who domesticated cattle. In humans, as in all other mammals, the ability to digest lactose (the sugar in milk) is lost during childhood. The gene that makes lactase (the enzyme that breaks down lactose) shuts off after a few years of service, because mammals don’t drink milk after they are weaned.
scale as well. Gene-culture coevolution is Exhibit C in the retrial of group selection.
But did gene-culture coevolution stop at that point? Did our genes freeze in place, leaving all later adaptation to be handled by cultural innovation? For decades, many anthropologists and evolutionary theorists said yes.
Rather than selecting foxes based on the quality of their pelts, as fox breeders would normally do, he selected them for tameness. Whichever fox pups were least fearful of humans were bred to create the next generation. Within just a few generations the foxes became tamer. But more important, after nine generations, novel traits began to appear in a few of the pups, and they were largely the same ones that distinguish dogs from wolves. For example, patches of white fur appeared on the head and chest; jaws and teeth shrank; and tails formerly straight began to curl. After just thirty
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genetic evolution greatly accelerated during the last 50,000 years.
Genes are constantly turning on and off in response to conditions such as stress, starvation, or sickness.
Fast evolution is Exhibit D in the retrial of group selection.
A catastrophic volcanic eruption 74,000 years ago from the Toba volcano in Indonesia may have dramatically changed the Earth’s climate within a single year.88 Whatever the cause, we know that almost all humans were killed off at some point during this time period. Every person alive today is descended from just a few thousand people
who made it through one or more population bottlenecks.
Group selection does not require war or violence. Whatever traits make a group more efficient at procuring food and turning it into children makes that group more fit than its neighbors.
Group selection pulls for cooperation, for the ability to suppress antisocial behavior and spur individuals to act in ways that benefit their groups.
Exhibit A: Major transitions produce superorganisms.
Exhibit B: Shared intentionality generates moral matrices.
Exhibit C: Genes and cultures coevolve.
Exhibit D: Evolution can be fast.
In September 1941, William McNeill was drafted into the U.S. Army. He spent several months in basic training, which consisted mostly of marching around the drill field in close formation with a few dozen other men. At first McNeill thought the marching was just a way to pass the time, because his base had no weapons with which to train. But after a few weeks, when his unit began to synchronize well, he began to experience an altered state of consciousness:
Words are inadequate to describe the emotion aroused by the prolonged movement in unison that drilling involved. A sense of pervasive well-being is what I recall; more specifically, a strange sense of personal enlargement; a sort of swelling out, becoming bigger than life, thanks to participation in collective ritual.
McNeill studied accounts of men in battle and found that men risk their lives not so much for their country or their ideals as for their comrades-in-arms.
Many veterans who are honest with themselves will admit, I believe, that the experience of communal effort in battle … has been the high point of their lives.… Their “I” passes insensibly into a “we,” “my” becomes “our,” and individual fate loses its central importance.… I believe that it is nothing less than the assurance of immortality that makes self sacrifice at these moments so relatively easy.… I may
