Our Brains Are Stuck in the Stone Age

How ‘evolutionary mismatch’ affects our weight, behavior, and overall health

NNext time you’re craving sugar and you reach for that candy bar thank your ancestors because their behaviors — like hoarding rare sugary foods like fruits during droughts or famines — are still wired in our brains. In the thousands of years since our world has changed (sugary food is abundantly available these days) but our brains remain the same.

This concept, called evolutionary mismatch, is one way for psychologists to study human behavior. “Our brains are wired for certain conditions, but our surroundings no longer match those conditions,” says Glenn Geher, professor of evolutionary psychology at the State University of New York, New Paltz. “In other words, we have stone-age brains in modern environments.”

While pursuing his PhD in social psychology, Geher realized how much evolution shows up in contemporary life. “A speaker presented in our class, and he was taking all these powerful evolutionary concepts and shedding light on issues of social psychology,” Geher says. “I really started seeing all human behavior from that point through the lens of evolutionary psychology.”

Geher now studies, teaches, and writes about evolutionary mismatch and its health implications.

I talked to Geher about how evolutionary mismatch comes up in modern society, how people can alter their behaviors for better health, and if our brains will ever catch up to the times.

This interview has been edited and condensed for clarity.

Elemental: What is evolutionary mismatch for human beings?

Glenn Geher: Any organism evolves under certain conditions, and mismatch occurs when you have the organism outside of those conditions, especially for an extended period. When that’s the case, things don’t always work out well.

For example, zoos used to keep monkeys in little cages. But monkeys are primates like us — they’re social like we are, and they’ve evolved to have more space. When zookeepers realized monkeys don’t thrive in cages, they were thinking about the idea of evolutionary mismatch.

Humans are in the same situation now, since technological advances have very much outpaced organic evolution. The advent of agriculture about 10,000 years ago was the biggest game-changer.

For example, before agriculture, not a single human ever ate processed food. For the lion’s share of the human evolutionary experience, the sweetest thing you’d find was sweet berries or grapes.

Now, with modern technology, you can put mediocre cupcakes or cookies out at a kid’s birthday party next to the best grapes in town, and you know you’ll be wrapping up those grapes at the end of the party. When the things we have evolved to crave are readily available, we always lean toward the stimuli that offer instant satisfaction.

The technology of agriculture plays and preys on the fact that our brains still crave the sweeter things — the sweeter food, and the instant-gratification experiences. It’s like giving candy to a baby.

We have all these adaptations with preferences for things that are now unhealthy for us. The world just preys on parts of our evolved brain.

What’s the connection between evolutionary mismatch and the obesity epidemic?

We’ve evolved to try to eat things that would have put fat on our bones because under ancestral conditions, there would have been famine or drought. Our ancestors evolved to prefer food that was high calorie, high sugar, high fat—because those things were rare back then.

We’ve also evolved to be lazy because ancestral environment and activities forced people to expend a ton of energy, so being lazy was adaptive under those conditions. But now, you can be lazy and eat junk food all day long and it won’t have a positive outcome anymore.

Our modern conditions are mismatched from the conditions where our preferences developed.

I always give the example of Type 2 diabetes, which is partially a result of a poor diet and obesity. It’s usually given as a classic example of what we call a “disease of civilization.” This can happen because our brains are wired to crave sugar, which is now readily available.

In other words, technology and agriculture have advanced, but our brains haven’t yet understood the implications of that technology.

How can we overcome behaviors that could potentially be harming us?

Understanding the concept of mismatch is a good first step. Once I understood the concept of evolutionary mismatch in my early thirties, I changed my diet to eliminate processed food. For the last 20 years, I’ve eaten 90% only natural foods. I got back to my high school weight. I eat as much as I want. It’s so simple—if you use the rule of pretending other foods don’t exist — if you go back to what your ancestors would have eaten.

It’s the same with exercise. I’m a marathon runner. I make a point of trying to get the amount of activity our bodies evolved to get in nomadic conditions.

Does the mismatch have any social or mental health implications?

Loneliness is one example. Before the advent of agriculture, our ancestors were nomads. Nomadic groups have to be capped at around 150 people because if you think about it, logistically, you can’t have a group of a million people trying to cross a mountain 10 miles away.

Our minds have evolved to be in those small groups, where we knew everyone and there weren’t any strangers. Building bonds of trust in those clans was really important, but if you’re walking across 42nd Street in New York, you don’t have an obligation to build trust with those people you walk by. You’ll probably never see them again.

That’s why some people feel lonely when they’re surrounded by millions of people in a city. We evolved to be in small scale conditions where we knew people, and being surrounded by so many strangers isn’t something our minds evolved to deal with.

There’s also cell phones. People can amplify their self-presentation in ways we never could before with photos or descriptions on a dating site. We can be anonymous in our communication or communicate with someone at the drop of a hat.

As technology continues to advance, will our brains catch up to overcome the mismatch?

It’s a really depressing answer, but no.

Brains haven’t had a chance to catch up with technological evolution. If you look at an XY axis and see the rate of evolutionary advancement over the last 10,000 years, the human brain has pretty much stayed a flat line. Technology would be an incredibly steep curve, and it’s only getting worse. For us to catch up to technology would take thousands of generations.

Look at deer. Deer are not car savvy. Cars have been around for about 100 years, and deer live about 10 years, so that’s 10 generations of deer who had a chance to figure out how to dodge cars. You’d think that the ones that were car savvy would adapt to over-reproduce compared to others. That’s basically the concept of “survival of the fittest.” But evolution doesn’t work that quickly.

It’s the same with the human brain. We have all these adaptations with preferences for things that are now unhealthy for us. The world just preys on parts of our evolved brain.

What’s your hope for the future of evolutionary psychology and public health?

Evolutionary science is advancing in lots of fields. We understand the human condition and health better than we ever have. I hope we can better understand these things and educate people, and make decisions and policies that take our evolved nature into account.

I brought up to my students the idea of a federal Office of Human Implications, kind of like the FDA. What if there could be people educated in evolutionary science who could find flaws in technology before it went to the public?

For example, when McDonald’s first came on the scene and was a wild success, there’s no way there were people at the top suggesting we consider the implications of evolutionary mismatch.

But now, human science has caught up. Hopefully, into the future, we’ll have some formalization of this understanding within organizations or at a government level to guide policies that would truly be healthy for people considering evolutionary mismatch.

Writer-mom hybrid. Health & psychology stories in NYT, WaPo, Allure, Real Simple, & more.

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