 Your work on animals, we have a little time to talk about this. You've studied chimpanzees. They're termite fishing, they're ant dipping, they're nut cracking. How conservative are chimpanzees? How much is their chimpanzee culture in addition to their instincts? Right. So chimps definitely have some culture. They do some social learning. They learn a few tools. The key difference between other animals and humans is that human culture is cumulative. So we're able to learn stuff from the previous generation, add a little bit to it, pass it down to the next generation, add a little bit to it. And in chimps, because of their social structure and part maybe because of their cognition, they're not able to generate this cumulative cultural evolution. So nothing that a chimp does, nothing that he does, he couldn't figure out by himself. So he might get it more easily by learning it from another chimp, but nothing is so complex that he couldn't figure out by himself. And in humans, even in the simplest human societies, hunter-gatherers, there's tons of things that no single individual could figure out in their lifetime. And you're completely dependent on this body of knowledge, know-how, norms that's bequeathed to you from prior generations just to survive. There's some breakthrough in the past that's quite remarkable, what are now human beings start doing something that the other great apes don't. And this is all speculative, of course, but what in your opinion is that confluence of events that leads to this great filter, what are now human beings pass through it, but the other great apes basically do not? Yeah, so that's the startup problem. And so the key thing to understand the startup problem is how humans went up down this special trajectory. So the way I think about it is you want to think about natural selection as investing either in bigger brains that make you better at figuring out stuff out by yourself, better at individual learning, or better at cultural learning, at learning from others. And when there's not very much interesting things, interesting tools, techniques, ideas in the minds and behaviors of other members of your social group, individual learning is better because learning from others doesn't get you anything because nobody else in the group has anything. So what you need is a situation where you're able to have useful ideas in the minds of other members of your social group. So in the book I make the case that when humans are on the savannah as bipedal apes, the predator guild was probably much larger. So humans have a chimpanzee like brain except they lived in larger groups and they would have had to be more social with each other, so there's a chance they could have crossed this threshold and started down this road. There's a few other factors like the climate was changing in a way that would have favored cultural evolution. So a few other things play into it, but that's the basic idea. But it's odd in a way there are not intermediate species, or maybe there were and we killed them off, but like Neanderthals, denisovans, might they have been smarter than humans? Yeah, so in the book I make the case that Neanderthals were probably smarter than us, because in primates, basically its overall brain size predicts how good you are on various cognitive tests. And Neanderthals are our cousins, so they're around say from 200,000 to 25,000, and they have larger brains than us. We're about 1350 cc's, Neanderthals are 1500, so we should expect them to be smarter than us. The difference is the African variant, we're the African variant. We had larger groups because we were living in a climate that allowed us to have a larger collective brain, so we were able to generate probably bows and arrows, other fancy technologies, and then we move into Europe and exterminate the Neanderthals.