New Essay: How Culture Drives Human Evolution

An excerpt from the first essay of Living Ideas

Hi there, subscriber!

Today is a big day. I’ve just published the first essay of this Living Ideas series entitled: How Culture Drives Human Evolution: Reviewing “The Secret of Our Success”.

Below is an excerpt from the essay, which you can read in full here. The reason I’ve only sent you an excerpt is that the full essay won’t fit in an email.

This will probably be a one-time thing — I wanted to start off with a bang, and this essay covers a lot of ground. Going forward, you should be able to read the full essays without leaving your inbox.

Excited to hear your thoughts on it, and I hope you enjoy the read!

Cheers,
Sachin


If you want cool new technology, is it better to be social or to be smart?

Your intuition probably tells you that it’s better to be smart. In school, for example, we probably don’t expect the hyper-social people to go on to be great inventors and technologists. But this general observation, which may apply for individuals, likely does not apply for populations. 

Henrich poses the following thought experiment to explain why:

Consider two very large prehuman populations, the Geniuses and the Butterflies.

Suppose the Geniuses will devise an invention once in 10 lifetimes. The butterflies are much dumber, only devising the same invention once in 1000 lifetimes. So, this means that the Geniuses are 100 times smarter than the Butterflies.

However, the Geniuses are not very social and have only 1 friend they can learn from. The Butterflies have 10 friends, making them 10 times more social. 

Now, everyone in both populations tries to obtain an invention, both by figuring it out for themselves and by learning from friends. Suppose learning from friends is difficult: if a friend has it, a learner only learns it half the time… do you think the innovation will be more common among the Geniuses or the Butterflies?

Well, among the Geniuses a bit fewer than 1 out of 5 individuals (18%) will end up with the invention. Half of those Geniuses will have figured it out all by themselves. Meanwhile, 99.9% of Butterflies will have the innovation, but only 0.1% will have figured it out by themselves. Keep in mind that the Geniuses were 100 times smarter than the Butterflies whereas the Butterflies were only 10 times more social. 

Bottom line: if you want to have cool technology, it’s better to be social than smart.”  - The Secret of Our Success, pg. 213

This is one example of how applying population thinking and a cultural-evolutionary lens can lead to some surprising and counterintuitive conclusions. I’ve chosen to highlight the 10 concepts below from The Secret of Our Success because they all share that trait. 

1. Human Beings Are Butterflies, Not Geniuses

As humans, we certainly feel like we’re the most important life form on the planet. But maybe we only think this because we’re biased. What can the evidence tell us about our own success as a species?

Henrich begins his book with some impressive stats about our ecological dominance:

  • Humans take up 100x more biomass than any large species that has ever lived, including the dinosaurs.

  • Together with our pets and domesticated animals (sheep, cows, etc.), we account for 98% of the biomass of land-bound animals with a spine.

  • If you put every human being in existence on a scale and weighed us against other species, only ants would even remotely be in the same ballpark. But there are 14,000+ species of ant, and only one species of human.

Thus we’re a clear outlier in terms of ecological success. We’re also unequalled in terms of our control over — and unintended impact on — our environment. For example, we’ve altered more than one-third of the earth’s land surface to serve our agricultural or industrial needs. No other species could conceivably travel to other planets, nor split the atom. The question is, why?

As mentioned earlier, the intuitive answer is that we’re simply that much smarter than other animals because the right mix of environmental factors in our past led to the genetic development of bigger brains in our lineage than in any other species.

But what exactly caused us to have these big brains, and whether it is brain size alone that accounts for our intelligence, is the source of considerable controversy among scholars. They’ve come up with a large number of competing “intelligence hypotheses”, none of which appears to have reached universal consensus.

Henrich is one of the foremost advocates of the “Cultural Intelligence Hypothesis”. The claim here is that information transmitted culturally, which accumulates over generations via a blind evolutionary process (and is thus “cumulative”), produces useful adaptations that drastically improve our odds of survival and reproduction.

As discussed in greater detail in sections 3 and 4 below, this cultural process created genetic selection pressure that improved our memory and information processing power in order to more effectively store and retransmit cultural information, and also produced mental tools and pre-built solutions that augment our intelligence considerably.

Cultural adaptations themselves take various forms — everything from physical technologies like how to light a fire or build a bow and arrow, to social technologies like ritual dances or sacral rites that increase social cohesion within a tribe, to mental tools like terms for “left” and “right”. These adaptations are selected for because of their capacity to improve the survival and reproduction odds of human groups who hold them.

The capacity to learn and pass on such cultural adaptations (cumulative cultural learning) both explains our success, Henrich argues, and drove the threefold expansion in our brain size from cm3 to 1350 cm3 in the last ~5 million years. To the extent that we have developed greater innate intelligence than other animals, it was primarily driven by the need to learn, process, and pass on cultural adaptations — not vice versa.

In other words, raw human general intelligence wasn’t responsible for the origin of culture and cultural evolution. It’s the other way around!

To illustrate that cumulative cultural learning is the unique advantage/superpower of human beings, not brain size or raw intellect, Henrich brings up various points:

  • Brain size is the strongest predictor of cognitive abilities (raw intelligence) in primates. Neanderthals had bigger brains than us, and therefore were likely smarter innately, but were much less successful, both ecologically and technologically. 

  • In a laboratory showdown between chimps, orangutans, and young kids without the advantage of culturally-acquired mental tools (like algebra), the only way in which humans far outperformed other apes was in their social learning abilities. With respect to spatial, quantitative, and causal reasoning, humans were not much innately better (findings by Michael Tomasello, Esther Hermann, et. al. published in 2007 & 2010).

  • In a test comparing the working memory and information processing speed between chimps and humans conducted by Japanese researchers Sana Inoue and Testuro Matsuzawa, the humans were only slightly better when it comes to working memory, while the chimps dominated in terms of information processing speed.

  • In a strategic game called matching pennies played between chimps and humans, chimps were far faster at zeroing in on a game theory optimal strategy, while the humans struggled. 

Therefore, there is little compelling evidence that, even now, humans stripped of culturally-acquired tools have more raw intelligence than other apes or extinct hominids (Neanderthals, who seem to have exceeded us in brain size, may even have been innately smarter). Instead, our real superpower is cultural learning. 

Implication: Human Intelligence Is Not Uniquely Rational

I have to confess that I found Henrich very persuasive here, despite the fact that my beliefs prior to reading his work were directly in opposition to what he’s saying. I’ve always basically aligned with Plato’s theory of the tripartite mind, which implies in modern terms that our large neocortex, where higher reasoning occurs — Plato’s “λογιστικόν” (logistikon) — is what separates us from the animal world and makes us intelligent.

There are several versions of this narrative of intelligence, not all attributed to Plato, which put higher-order reasoning at the center of what defines human intelligence. For example, Aistotle, spoke of man as being distinguished by “having reason” (λόγον ἔχον) in the Nicomachean Ethics.

I’ve found that this “Promethean script”, as Jonathan Haidt recently called it, is difficult to maintain against the strong case Henrich makes for the Cultural Intelligence Hypothesis. 

While we can still value human reason, the evidence seems to contradict the intuitive idea that our ability to reason — or to think ahead (the meaning of Prometheus’s name) — is what caused us to become intelligent and develop the ability to (for example) create fire. 

This matters because I think it redefines what it means to be human. What makes us unique, and even what makes us sentient, is that we alone of all life forms can transmit cultural information. This means we can transmit evolutionary adaptations by way of memes (Dawkins’ proposed term for the atomic unit of cultural selection), whereas all other organisms rely on genes to transmit such adaptations. 

Henrich says that “it’s not our intelligence”, nor even our reason, that makes us special. The explanation he offers instead is far more complex, counterintuitive, and fascinating.


The passage above is an excerpt from my new essay, “How Culture Drives Human Evolution.” You can read the full essay here.