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How did humans spread to all ecosystems?

You might assume that the humans, given our superior intelligence, are the team to beat. But do you or your colleagues know how to make bows and arrows, nets, water containers, and shelters? Do you know which plants are toxic?

Imagine a game of survival that pits a troop of capuchin monkeys against you and your work colleagues. Both teams would be parachuted into a remote African forest, without any equipment: no matches, knives, shoes, fish hooks, clothes, antibiotics, pots, ropes, or weapons. After one year, the team with the most surviving members would be declared the victor. Which team would you bet on?
You might assume that the humans, given our superior intelligence, are the team to beat. But do you or your colleagues know how to make bows and arrows, nets, water containers, and shelters? Do you know which plants are toxic?
Can you start a fire without matches? Can you make fish hooks or natural glues? Do you know how to protect yourself from big cats and snakes at night? The answer to most, if not all, of these questions is probably "no," meaning that your team would likely lose to a bunch of monkeys - probably pretty badly.
This raises an obvious question. If we cannot survive as hunter-gatherers in Africa, the continent where our species evolved, how did humans achieve such immense success relative to other animals and spread to nearly all of the earth's major ecosystems?
Here's a key piece of the answer: We are a cultural species. Our unique psychological capacities allow us to learn from one another over generations, facilitating a cumulative cultural evolutionary process that produces increasingly complex and sophisticated technologies, languages, bodies of knowledge, conceptual toolkits, and adaptive heuristics. The power of this process arises not from raw individual intelligence, but from the reinterpretation of the serendipitous insights and mistakes that our intelligence produces.
The foundation of our ability to form cooperative communities, organisations, and societies arises not from innate cooperative tendencies, but from the specifics of the social norms that we learn, internalise, and enforce on others. While our innate motivations do play a role, they are harnessed, extended, and suppressed by social norms, which form the institutional skeleton that allows our innate inclinations to operate.
This novel view of human nature and society generates some important insights.
First, as a cultural species, humans acquire ideas, beliefs, values, and social norms from others in their communities, using cues of prestige, success, sex, dialect, and ethnicity. We pay particular attention - especially under conditions of uncertainty, time pressure, and stress - to domains involving food, danger, and norm violations. Changing people's behaviour begins with an understanding of our cultural nature, not our rationality.
Second, we gradually internalise the social norms that we acquire through a culture-driven process of self-domestication.
Third, the most potent social norms harness aspects of our evolved psychology.
Fourth, our ability to innovate depends on the size of our collective brain, which depends on the ability of social norms to encourage people to generate, share, and recombine novel ideas and practices.
Fifth, there is a fundamental link between institutions and psychology. Because different societies have different norms, institutions, languages, and technologies, they also have different ways of reasoning, mental heuristics, motivations, and emotional reactions.
Finally, humans lack a certain degree of rationality, making us terrible at designing effective institutions and organisations - at least for now.
I am hopeful that as we obtain deeper insights into human nature and cultural evolution, this can be improved. Until then, we should take a page from cultural evolution's playbook and design systems that use variation and selection to make institutions compete. That way, we can dump the losers and keep the winners.
By examining the rich interaction and co-evolution of psychology, culture, biology, history, and genetics, we have the possibility to gain important insights into human psychology.
This scientific road has rarely been traveled. It promises an exciting journey into unexplored intellectual territory, as we seek to understand the peculiarity of our species.
Joseph Henrich is Professor of Human Evolutionary Biology at Harvard University