How These People Evolved to Permanently Live at Sea | Joe Rogan and Nicholas Kristakis

There's a sense in which as we create those environments, we actually change ourselves as a species. There's this set of ideas that's known as gene culture coevolution. And the idea is that we create certain kinds of cultural environments. Those kinds of cultural environments advantage certain ones of us, making those of us that are born with certain abilities better off, which then leads to those environments being created even more. Let me give you an example of that. The most famous example of this is something known as lactase persistence. So many people, not about half the world, adults can drink milk. The other half cannot. They get lactose intolerant. Well, why can you drink milk as an adult? Have you ever thought about that? Like why are you capable of drinking milk as an adult? In our ancestral state, actually up till about 10,000 years ago, only babies could digest milk because only babies had milk. Babies would suckle at their mother's breasts and have milk, and then they'd be weaned, and then they would never drink milk again. There'd be no milk to drink. There was therefore no reason for any adult to be able to digest lactose, which is the principle sugar in milk, because there was no lactose in your diet. You didn't encounter milk. So human beings were able to digest lactose when they were babies. They lost that capacity, all human beings. When they got to about two or three or four or five when they weaned, they no longer were able to digest milk. The enzymes in their body were programmed, as it were, to only work when they were infants. Well, about between three and 9,000 years ago, in multiple places in Africa and in Europe, human beings suddenly domesticate animals. We domesticate milk-producing animals like cattle and sheep and goats and camels. And now all of a sudden, there's a supply of milk around us. Because of our cultural innovation, because of the thing we invented, we created the domestic breeds. Now we have milk. Now, therefore, those among us who were mutants, who were born with the ability to have our lactase, the enzyme that digests lactose, persist into adulthood. This is known as lactase persistence. Those of us who had that would have a survival advantage, because we could have another source of calories that the rest of the people in our group couldn't consume. They couldn't drink milk like we could. And we had a source of unspoiled water during times of drought. We could drink milk. Everyone else had to drink this filthy water that they didn't have access to. So those among us who had these qualities could reproduce better, had a survival advantage. It turns out that this has happened several times. This has been well-documented. The genetics of this has all been worked out several times in the last three to 9,000 years. Because of a human cultural product, we have evolved to be a slightly different genetically. And it doesn't stop with cows. I think that when we invent cities, about over 5,000 years ago, so we invent agriculture about 10,000 years ago, it's debated exactly when we invent cities. But between 5 and 10,000 years ago, we start having fixed settlements. Earlier you and I were talking about population density and having to live with other people, which is not our ancestral state, not packed, not with other people. We always lived socially. I think that as we invent cities, people with different kinds of brains are better able to survive in cities. So now that we've invented cities, we're advantaging people with certain kinds of brains. And therefore, I think in 1,000 or 2,000 or 5,000 years, just like the milk example, there'll be different people as a result of something we humans manufactured that we made. And I could keep giving you examples of this. In the book, I have another example of a...they're called the Cenomads. They live in the Philippines. These are people who don't live on land. They live on houseboats that sail around the Pacific. For thousands of years, they've had this lifestyle. And they dive for their food, dive. So they forage on the seabed. They are the world's best free divers. They spend hours per day underwater. They can hold their breath longer than anyone else. And they do it nothing except with weights and wooden goggles. They dive down into the seabed and forage, and they hunt underwater with spears. They hunt underwater with spears. It's mind-boggling. Wow. But they have evolved to have different spleens and different oxygen metabolism than you and I. So those among them that could survive the dives fed their families, made more babies, and now we think this happened 2,000 years ago, they're different. The ones that couldn't died. So their invention of a seafaring way of life, their invention of a way of living at sea, the boat technology, the spear fishing technology, the invention of those technologies creates an environment, a cultural environment around them, which modifies natural selection and changes the kind of genes that those people have.