So is it possible to truly eat like our ancestors?
Trying to emulate what people ate 10,000 or 100,000 years ago is really difficult. Our foods have changed so much that virtually every item in a supermarket is drastically genetically different from its prehistoric equivalent. This is what humans do: We modify foods so that they become more palatable and digestible.
I'm not out to diss paleo diets. Clearly a lot of people who eat that way are happy with it and feel like they're healthy. It's almost certainly better than living off junk food. But it seems to me that decisions about what's going to be good for you have to be based on data, not just trying to eat what everybody ate tens of thousands of years ago.
Do you think the rise of these types of diets is a response to junk food culture?
Ironically one of our big problems in the developed world is an abundance of calorie-rich food. There is a lot of research on the "thrifty genotype" idea—that our ancestors evolved to deal with boom and bust food availability. If you're always in boom, it's going to have unexpected consequences for your health. That's a good example of how we need to consider evolutionary heritage when we think about food and how it affects our physiology. But that's different from saying we should eat exactly like our forebears.
What do you think of fitness regimes that advocate exercising like a hunter-gatherer?
There are people who argue that our ancestors ran mainly in short, sustained bursts: fleeing a predator or chasing down prey. As a result, they advocate brief spurts of high-intensity training. But there is also convincing evidence that our ancestors could run for sustained, marathon-like distances, which may have been selected for because it helps in what's called persistence hunting, where you run down prey until it drops from exhaustion.
As with food, to me the more interesting thing is not to try to model our exercise regimes on what early humans did, which we will probably never know for sure, but instead to use the limited data we do have as a jumping-off point and then develop ideas about how best to exercise using information from the here and now. The point is to get inspired by the past, not constrained by it.
What about the view that a lot of diseases arise because of the mismatch between our genes and modern lifestyles?
This is the idea of so-called "diseases of civilization." There have been enormous increases in Type 2 diabetes and autoimmune disorders. There are many diseases that have only arisen in the last few centuries or that seem to arise only among people living in first-world conditions. There are communicable diseases like measles that only happen when people are in groups of a certain size. Because of that, I suppose you could argue we should live in tiny villages and then we wouldn't get measles. To me a better solution seems to be the measles vaccine.
So you think that this logic about "diseases of civilization" can be taken too far?
Yes. There has been lots of discussion of cancer as a modern scourge, but this isn't supported by the data. It turns out that ancient remains show about the same incidence of cancer as we have, with the exception of lung cancer. This is tied to tobacco use, which obviously is more modern. But overall the data doesn't support the idea that we didn't get cancer until we started living this horrible modern life.
Do you think the type of nostalgia driving these trends can be harmful?
What's harmful is when you misunderstand the way evolution works and end up worried that because humans didn't use to do X, we shouldn't do X now. Almost all traits are a trade-off. Individuals with longer legs might survive better because they can run away from predators. But they might also get colder faster, because they lose more heat through their legs. The advantage or disadvantage depends on the environment you're in now.
Find out more in New Scientist’s gallery: "Paleo-trends: Separating fact from fantasy."
This article originally appeared in New Scientist.