Kyle Harper: belief

Transcript context

…One thing I'm really curious about is what effect these diseases through history have had on the cognitive functioning of people. You discuss this in the chapter about more recent history of the great divergence and probably attributed the productivity of Europe that they were able to have public health earlier. But literally going back thousands of years, you mentioned, for example, that Caesar was 5'5" and that was considered tall during his period. Did the same diseases and malnutrition that caused these physical health effects also mean that the average IQ was much lower, because when you're a kid you're sick and that steals away nutrition from brain growth or something? Yeah. Short answer, yes. Long answer, we know that in the modern world, say over the last 250 years, first in Western European societies and their settler offshoots and then more globally and more rapidly globally, there have been really deep physiological changes in the average human. We're talking about populations with distributions. What's happened is really two things. One is there's more energy per capita. People eat more, they eat more calories, and they eat better calories. They eat lots of bad stuff too, but people eat more. Two, the burden of infectious disease has been lowered. Growth for a human is a very complicated trait that's influenced by genetics. I was never destined to be super tall. But it's also affected by environment, which includes nutrition and what you spend either doing labor or what you spend fighting infectious disease. Infectious disease imposes a huge burden on the body. The immune system is extremely metabolically expensive. If your childhood is spent just fighting infectious diseases, you're going to struggle to invest energy in growth. There's massive increase in the size of populations over the last 250 years and even though it's an even more complicated trait, this improves people's cognitive abilities. People are smarter. May not feel like it—I think it has rapidly leveled off—but people are more intelligent today than they were 100 years ago. Their brains are better nourished and their bodies spend less time fighting pathogens. I think there's no doubt that pre-industrial populations, and again, populations—so you still have your Isaac Newtons, who whatever infected him as a kid, didn't slow him down—but at the population level, I think there's no doubt that not only were pre-industrial populations shorter, this is just a total fact that we know from their bones, but they probably also, on average, had a lower distribution of cognitive abilities. But with a big distribution. You have a great profile in the book about living in London in the 18th century and just how disgusting it was.…

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