麻豆传媒

Find out more in our gallery: 鈥�Palaeo-trends: Separating fact from fantasy鈥�

Your book is about pseudoscientific ideas you call 鈥減alaeofantasies鈥�. What are they?
They stem from the idea that evolution makes minuscule changes over millions of years, so we haven鈥檛 had enough time to adapt to the modern industrial world 鈥� and that we would be healthier and happier if we lived more like our ancient ancestors.

Is there any truth to the idea that we haven鈥檛 evolved fast enough to cope with modern life?
To some extent it is true. Our bodies are ill-suited for sitting at computers all day, for example. Because humans evolved in an environment where they were not crouched over computers, sitting that way all day is going to have ill effects. But it鈥檚 more nuanced than that. Being bipedal has a lot of costs on the human skeleton, too. Should we all long to be quadrupeds? It just doesn鈥檛 make sense.

What is driving the tendency to idealise the way ancient humans lived?
There is this caricature that organisms evolve until they get to a point when they鈥檙e perfectly adapted to their environment, then heave this big sigh of relief and stop. Anything that happens to them after that is disastrous.

You see this attitude in what can be referred to as 鈥減alaeo-nostalgia鈥� 鈥� the notion that we were all better off before agriculture, or civilisation or the industrial revolution. It鈥檚 not to say life has been unmitigatedly getting better. But it鈥檚 more helpful and accurate to see that all organisms are constantly evolving. There has been no point in our past when we were perfectly adapted to our environment.

鈥淭here was no past point when we were perfectly adapted to our environment鈥�

I鈥檓 not dismissing the idea that you need to look at our evolutionary heritage to think about what鈥檚 best for us health-wise. But when you start plucking out pieces in an oddly specific way, you can run into trouble.

Are palaeo diets, which usually involve eating lots of meat and avoiding grains or dairy, examples of this type of specific selection?
These are predicated on the idea that there was a certain way humans ate 100,000 or 15,000 years ago 鈥� the era people want to hark back to varies. I think everybody agrees that we evolved eating certain things and we鈥檙e going to be very unhealthy if we subsist on Diet Coke and Cheetos. But it gets more complicated when you look at the details. Should we eat a lot of meat, less meat? Should we eat dairy?

How much do we know about early human diets?
We don鈥檛 really know what they were eating. It鈥檚 turning out that they may have eaten more starch and carbohydrates than we had realised. They also ate different things in different parts of the world. So it鈥檚 hard to come up with this one perfect human diet that everybody was eating. Plus our genes have changed in the last 10,000 years. Lactase persistence 鈥� the ability to digest milk as adults 鈥� is the poster child for this. Our genes have changed extremely rapidly so that at least some populations of humans can digest milk into adulthood.

And just as with lactose, it turns out that in human populations that consume a lot of starch, there are more copies of genes that allow starch breakdown. All of this suggests that evolution is happening all the time, and much more quickly than people think.

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鈥檓 not out to diss palaeo-diets. Clearly a lot of people who eat that way are happy with it and feel like they鈥檙e healthy. It鈥檚 almost certainly better than living off junk food. But it seems to me that decisions about what鈥檚 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 鈥渢hrifty genotype鈥� idea 鈥� that our ancestors evolved to deal with boom and bust food availability. If you鈥檙e always in boom, it鈥檚 going to have unexpected consequences for your health. That鈥檚 a good example of how we need to consider evolutionary heritage when we think about food and how it affects our physiology. But that鈥檚 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鈥檚 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 鈥渄iseases of civilisation鈥�. 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鈥檛 get measles. To me a better solution seems to be the measles vaccine.

So you think that this logic about 鈥渄iseases of civilisation鈥� can be taken too far?
Yes. There has been lots of discussion of cancer as a modern scourge, but this isn鈥檛 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鈥檛 support the idea that we didn鈥檛 get cancer until we started living this horrible modern life.

Do you think the type of nostalgia driving these trends can be harmful?
What鈥檚 harmful is when you misunderstand the way evolution works and end up worried that because humans didn鈥檛 use to do X, we shouldn鈥檛 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鈥檙e in, now.

This article appeared in print under the headline 鈥淭he lure of the Stone Age鈥�