Want culture? Climb down from your tree

The secret of our success

[This post is a summary of Chapter 16 of Joseph Henrich’s The Secret of Our Success]

Why only us?

We are a uniquely social, powerful, and widespread species, with some very strange features. Yes, some non-human animals make tools, some have social learning, some have communication systems. The intelligence of non-human animals is elusive and often underestimated. At the same time, one species, and one species alone, has developed some anomalous capacities found nowhere else in nature: grammatically structured languages, enormous social groups, complicated food-processing technologies. One must be contrarian to the point of being deliberately obtuse, in order to deny that there is something special about humans that needs to be explained. Why is our species the only one that has developed in this way? How did there come to be this massive discontinuity between our species and other species, given that evolution trades in incremental tinkering?

In the Secrets of Our Success, Joseph Henrich takes a new crack at this venerable question. He thinks that perhaps the key development that launched humanity onto our strange and unique path was: descending from the trees. He tells a speculative but very compelling story about the downstream effects of this transition, and how they explain why we developed culture (and our cousin primates did not).

“Culture” is the operative word here. Henrich’s theory of human uniqueness cannot be understood without the context of the broader message of Secrets: Henrich argues that humans as individuals are not especially smarter than their ape cousins. We have built up cultural know-how that allows us to survive, but without this cultural know-how, individual humans are helpless and not particularly more generally intelligent, or have better/smarter instincts, than apes. Furthermore, to the extent that we are genetically anomalous—especially big-brained, hairless, weak, precision grips, small teeth and stomachs—these anamolies are an effect of culturally-driven natural selection. For example, once a species innovates some primitive food processing, for example “boil ‘em, mash ‘em, stick ‘em in a stew”, this can drive the evolution of small stomachs. For Henrich, the story of human uniqueness is a story of this kind of feedback loop: increased cultural know-how, leading to selection for bigger brains and better social learning, which in turn drives increased cultural know-how, which leads to bigger brains….and so on, until eventually you have a particularly weird great ape that is weak and hairless and causes mass extinctions and has put a flag on the moon.

by Dalle-3

In Henrich’s term, then, the question is: why didn’t other primates (or, say, dolphins) get launched into this feedback loop? Henrich argues that getting into this feedback loop is difficult for most species. There’s a start-up problem. In order for bigger brains to be a fitness advantage, there needs to be a lot of advantageous information to learn. For Henrich, that advantageous information is cultural know-how, like techniques for hunting, food processing, shelter, and so forth. In some sense, we are just part of a general trend that sometimes evolution will build big brains, because big brains are good for individual learning. But there is a limit, according to Henrich, to how far the advantages of individual learning can go.

But in order to create a lot of useful culture, you need big brains. How do you get into that feedback loop?

Henrich’s admittedly speculative answer is that being on the ground, and not in trees, is what allows cultural know-how to start developing. Here are the consequences of a primate species being on the ground:

1. It frees up your hands for tool use. Apparently captive chimps, which are more “grounded” than wild chimps, make more tools than wild chimps.

2. It’s easier for you to find tools left by other people.

3. It’s easier for you to see other people and hang out with them. (“Hang” is an inapt word in this context, since that’s precisely not what you’re doing).

4. It’s more important to group up with other people for protection.

Being on the ground means that you face more predators, and our ground-dwelling ancestors faced a terrifying array of ancient tigers and lions. Larger groups offer protection; and these larger groups will further juice the process of people messing around with tools and imitating each other.

by Dalle-3

Larger groups also produce new forms of social organization. Apparently, in smaller groups of chimps, the reproductive strategy that every male tries to follow is “fight as many males as you can for mating opportunities.” But with a large group, it becomes better for some males to try pair bonding – try to get multiple reproductive opportunities with one female, by hanging around her and taking care of her.

Pair bonding in turn allows for more kinship relationships. Apparently kinship is typically very hard for primates to keep track of. But if your dad hangs around your mom, you will hang around him too, and so will your (half) siblings. So you’ll get to know who they are. In contrast, without pair bonding, your dad does not hang around, and so it’s much harder to know who your dad and siblings are. As the number of people you grow up watching increases, this accelerates social learning. It also reduces the fitness downsides of being (or giving birth to) a big-brained, slow-developing learner: more people are hanging around, helping out, and pooling food resources.

On this story, descending from the trees is ultimately responsible for the large groups, extended relations, and accumulation of cultural know-how that makes it worthwhile for us to have big energy-consuming social brains, which both require and enable more savvy means of food production and childcare. This descent, according to Henrich, may be why humans came to be both uniquely powerful and uniquely sociable among the primates.