A Hunter-Gatherer's Guide to the 21st Century summary

Can you tell whether two lines drawn on a page are the same length or not? You may have seen the optical illusion in which two lines, of identical length, both have arrowheads at either end, going in opposite directions. Due to this difference, you perceive one line as being longer than the other. But not everyone falls for this illusion. 

Interestingly, people who grow up in hunter-gatherer societies, such as the San Bushmen of Southern Africa, have no problems seeing that the two lines are identical. However, for people who grow up in WEIRD countries – that is, Western, educated, industrialized, rich, and democratic – it’s almost impossible. 

The key message here is: WEIRD people grow up surrounded by unnatural geometry.

Unlike the San Bushmen, people in industrialized nations use sawmills to create timber with perfectly straight edges and precise corners. This might explain why we have trouble interpreting different line lengths – because we’re deprived of seeing more organic forms, we lose some of our visual abilities. This is just a theory, however, and it’s worrying that experts can’t say for sure that this is why we struggle with this sort of illusion. But one thing that does seem clear is that modernity is undermining our natural abilities in ways that we don’t fully understand, or often even realize. 

Our ignorance of how our environment affects our bodies manifests in other ways, too. For example, many people in WEIRD countries will suffer from appendicitis, a dangerous inflammation of the appendix, at some point. People in developing countries, however, rarely deal with appendicitis. 

Why?

Experts now believe that the appendix acts as a breeding ground for the good bacteria and microorganisms that live in our guts and help us digest our food. When we suffer from diarrhea and stomach upset, a lot of gut bacteria from our digestive tract gets flushed out of our bodies. But the appendix doesn’t lose its bacteria, and so can grow more of them to repopulate the tract. People in developing countries are exposed to more germs and different bacteria than those in WEIRD ones. We might think this is a bad thing – but our bodies are designed to go through this cycle of stomach upset and bacterial regrowth in the appendix. With our overly sterile and hygienic modern homes, we no longer suffer frequent digestive upsets, and so our immune systems and our gut bacteria get out of balance, ultimately leading to appendicitis in some people. 

So whether it’s our overly clean homes or the perfectly straight lines that surround us, the modern world is having an effect on our bodies and minds to which we’re not paying enough attention.