Max Bennett: uncertainty

Transcript context

…Yeah. The the the story of this chapter, incredible chapter. I've just I've just been studying it today in great detail, is the story of mentalizing, but I I would I would call it, you know, social complexification. Actually, that's a hypothesis of why our brains expanded so dramatically. So there was this extinction event. I think it was at the the Devonian extinction events and only birds and, you know, not many things survived. And then, we got the chance to kind of evolve after that and and our brains rapidly exploded and there are different theories about why that happened. You know, maybe it's because we had access to loads of calories in the form of, fruit, preferential access, and it gave us an incredible amount of, time and energy, the excess of which might have led to social complexification. But can can you just sort of give us a little bit of a background about that first piece, first? Absolutely. So we don't know. There's lots of speculations, but we don't know why this occurred with primates. But we do have, some really good evidence that at least part of what drove the sort of explosion in primate brains was social dynamics. And so Robin Dunbar did sort of the seminal work here, where what he showed is in primates, the encephalization quotient, which is just the ratio, like brain size, especially the neocortical ratio. So the ratio of the size of the neocortex to the rest of the brain, is extremely correlated with social group size in primates. So the bigger social group size you find in a group of primates, the bigger their neocortex seems to be relative to the their their body size. And what's so interesting is you don't see this in most other mammals. So this is not a standard correlation that applies across the animal kingdom. It seems to be this correlation that's very specific, to primates. There might be other mammals, but for most mammals, you don't see this correlation. And so, Robin Dunbar's famous social brain hypothesis is what drove the explosion in primate brains, is some form of social dynamic between people. And the more social relationships you're managing, the bigger your brain has to be. Now it doesn't explain what specifically happened in the brain, which is what we can get to with mentalizing and why that applies. But it does suggest that whatever drove this explosion in brain size, seems to be something correlated to social grouping. What's And interesting about primate social groups relative to not all mammals, but many other mammals, is they're very, very political. So many mammals live in sort of solitary sort of social lives where males mostly live alone and females will rear a child, and then usually they'll go off on their own. There are animals that live in sort of herds where they socially group together, but there's not really very rigorous hierarchies amongst them. But primates, especially apes, have these really complicated social structures with rigid hierarchies. So there truly is someone at the top of the hierarchy, and we can measure this through, primatologists have gone to painstaking lengths to verify this. For example, there's transitivity. So if you show that 1 primate tends to show a submissive signal to another primate, and that other primate shows a submissive signal to another 1, then it's almost definitely the case that that first 1 will show a submissive signal to the last 1. In other words, these these are real, rigid hierarchies. They're not like random interactions of submission and dominance. And what we see is 1 of the main ways you survive as a primate is you you successfully climb this hierarchy. And so what's so interesting is in many mammals, what makes someone the top dog or the sort of person who's the top of a hierarchy is is sort of bronze. It's just strength. fully climb this hierarchy. And so what's so interesting is in many mammals, what makes someone the top dog or the sort of person who's the top of a hierarchy is is sort of bronze. It's just strength. They're just show they're trying to flaunt who would win in a physical altercation, which evolutionarily is beneficial because if you can prevent actually fighting each other and just say this is what who would win the fight, then we both save energy just having these sort of fake battles. And then I can, if whoever wins gets to eat the food, etcetera. But with primates, it's not always the strongest 1 that reaches the top. It's the most socially savvy 1. And socially savviness comes into these alliances that are built within primates. So you'll see that people at the top of the hierarchy frequently will befriend and groom and come to the aid of certain other non family members. And those folks will thus reciprocate and come to their aid. And there are these really interesting dynamics that play out. You even see wars. So there's mutinies that take place in primate societies. So in this sort of soup of the way to survive and get evolutionary advantage as a primate is not perhaps only to make sure you get access to food, but to climb a social hierarchy. All of a sudden, there are these huge social pressures to be able to do things like infer what someone else would do in a certain circumstance or what someone knows or what you can get away with or how to change someone's opinion of you. And so what that you know, lines nicely to is what we see of the new brain regions that emerge in primates, most notably this brain region called the granular prefrontal cortex and these areas in the back of the brain called the superior temporal sulcus, temporal parietal junction. These brain regions across primates are highly implicated in what I call mentalizing, which is thinking about thinking. But the standard literature would call this just theory of mind. So being able to infer the intent or knowledge of someone else. And so it's very, it's easy to understand why this would be so adaptively valuable in a sort of politicking arms race where you're trying to sort of deceive each other. There's a great study that really revealed this with primates by Emil Menzel in the 19 seventies, and I love this this story. So he was trying to he was he had this, like, 1 acre forest. Do you wanna ask a question?…

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