From The Righteous Mind: Why Good People Are Divided by Politics and Religion, by Jonathan Haidt, pages 237 – 239.

In 49 BCE, Gaius Julius made the momentous decision to cross the Rubicon, a shallow river in northern Italy. He broke Roman law (which forbade generals to approach Rome with their armies), started a civil war, and became Julius Caesar, the absolute ruler of Rome. He also gave us a metaphor for any small action that sets in motion an unstoppable train of events with momentous consequences.

It’s great fun to look back at history and identify Rubicon crossings. I used to believe that there were too many small steps in the evolution of morality to identify one as the Rubicon, but I changed my mind when I heard Michael Tomasello, one of the world’s foremost experts on chimpanzee cognition, utter this sentence: “It is inconceivable that you would ever see two chimpanzees carrying a log together.”

I was stunned. Chimps are arguably the second-smartest species on the planet, able to make tools, learn sign language, predict the intentions of other chimps, and deceive each other to get what they want. As individuals, they’re brilliant. So why can’t they work together? What are they missing?

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.53 Solving the task earned the chimp or child a treat (usually a piece of food for the chimp, a small toy for the child). Some of the tasks required thinking only about physical objects in physical space-for example, using a stick to pull in a treat that was out of reach, or choosing the dish that had the larger number of treats in it rather than the smaller number. Across all ten tasks, the chimps and the two-year-olds did equally well, solving the problems correctly about 68 percent of the time.

But other tasks required collaborating with the experimenter, or at least recognizing that she intended to share information. For example, in one task, the experimenter demonstrated how to remove a treat from a clear tube by poking a hole in the paper that covered one end, and then she gave an identical tube to the chimp or child. Would the subjects understand that the experimenter was trying to teach them what to do? In another task, the experimenter hid the treat under one of two cups and then tried to show the chimp or child the correct cup (by looking at it or pointing to it). 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).

According to Tomasello, human cognition veered away from that of other primates when our ancestors developed shared intentionality.54 At some point in the last million years, a small group of our ancestors developed the ability to share mental representations of tasks that two or more of them were pursuing together. For example, while foraging, one person pulls down a branch while the other plucks the fruit, and they both share the meal. Chimps never do this. Or while hunting, the pair splits up to approach an animal from both sides. Chimps sometimes appear to do this, as in the widely reported cases of chimps hunting colobus monkeys,SS but Tomasello argues that the chimps are not really working together. Rather, each chimp is surveying the scene and then taking the action that seems best to him at that moment.56 Tomasello notes that these monkey hunts are the only time that chimps seem to be working together, yet even in these rare cases they fail to show the signs of real cooperation. They mak~ no effort to communicate with each other, for example, and they are terrible at sharing the spoils among the hunters, each of whom must use force to obtain a share of meat at the end. They all chase the monkey at the same time, yet they don’t all seem to be on the same page about the hunt.

In contrast, when early humans began to share intentions, their ability to hunt, gather, raise children, and raid their neighbors increased exponentially. Everyone on the team now had a mental representation of the task, knew that his or her partners shared the same representation, knew when a partner had acted in a way that impeded success or that hogged the spoils, and reacted negatively to such violations. 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.57 (Remember that a matrix is a consensual hallucination.) That, I believe, was our Rubicon crossing.

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.)</em?