Dozens of books tout the wonders of the “original human diet.” But how certain are we that there was an original diet? And if there was, exactly what did it include? More importantly: Did cavewomen and cavemen really eat dessert?
Nutrition Action’s David Schardt spoke to Marlene Zuk, professor of ecology, evolution, and behavior at the University of Minnesota, to get the facts on this popular diet.
Q: Is the Paleo diet our natural diet?
A: Some people claim that the cause of our so-called “diseases of civilization” that are diet related, such as diabetes or high blood pressure, is that our diets have changed radically since the time that human beings evolved hundreds of thousands of years ago. If we could go back to the way we were eating before, then we would be much healthier, they say.
It sounds pretty reasonable that if human beings evolved living a certain way and eating certain foods, and if we suddenly and rapidly change from those circumstances, there’s a risk of eating foods that are not necessarily the healthiest for us.
This idea is supported by looking at modern foraging peoples, who don’t eat Western diets and who certainly don’t seem to suffer as much from conditions like diabetes or hypertension. So, superficially a Paleo diet makes a lot of sense.
Q: But not when you look deeper?
A: Right. The problem is that it’s really a fantasy to try to construct what early humans were eating.
First of all, what do you mean by early humans? The word “Paleo” doesn’t mean much from a scientific perspective.
Are you talking about the ancestors of the genus Homo, such as Australopithecus? Are you talking about other members of the genus Homo, like Homo erectus? Or do you mean humans in Africa before they migrated out of that continent? Or is it after they left Africa? Or are we talking about people who were living the way that contemporary hunter-gatherers do—people who forage and hunt but don’t use agriculture?
Q: What difference would that make?
A: Because so far as we can understand, the diets of all these different early humans were really different. What people were eating 10,000 years ago at the dawn of agriculture, for instance, was doubtless not what people were eating 100,000 years before that.
Q: Didn’t their diets also depend on where they were living?
A: Yes. Picking a specific place or time to say, “Oh yes, we should be eating like those people,” doesn’t make sense. Is seafood okay on a Paleo diet? I suppose it depends on whether you think Paleo people were living on the northwest coast of North America, or whether you think they were in central Africa, in which case I don’t think there were a lot of shrimp available there.
Take the ancestors of the Inuit First Americans living in the Arctic. They get a lot of attention from Paleo enthusiasts because they relied on meat and seafood for food since so few edible plants grow up there. But the fact that nothing grows there just means that people can adapt to living without a lot of plant food. It doesn’t mean that they should live that way if they have a choice.
Q: The Paleo diet seems to assume that we’ve stopped evolving. Have we?
A: No. It’s clear that we are not the same as our Paleo ancestors. We’ve changed radically in some ways, like our resistance to diseases such as malaria, and not so radically in others, like the structure of our spines.
We didn’t evolve, evolve, evolve to a certain point and then go, “Phew! Done with that! We’re now perfectly adapted to our environment, and we can eat the same diet from now on. Then dang! Somebody developed agriculture, which was a mistake, and now we’re in trouble.”
There just wasn’t an ideal time and ideal diet from which we are now deviating.
Q: What’s an example of how humans continue to change?
A: People say that humans are the only mammals that continue to drink milk past weaning, which is absolutely true. Some of them then conclude that it’s unnatural for mammals to do this, and that it’s therefore much healthier for us to not consume dairy foods.
Well, the fact is that a great number of human beings have evolved an ability to keep digesting the lactose in milk throughout their lifetimes. That change happened just over the last 5,000 to 7,000 years, which is really quick from the standpoint of evolutionary change.
So saying that we should eat only what our ancestors ate before this genetic change happened makes as much sense as saying that we should eat only what our mammalian ancestors ate before they came down from the trees and started living on the ground.
That’s not to say that there aren’t some people who have trouble digesting milk, but that’s different from saying that all people, all the time, would be better off without it.
Q: The Paleo diet shuns grains. Did early humans ever eat them?
A: The absence of starchy foods on a Paleo diet is really interesting because it’s based on a fantasy of what our ancestors ate. Over the last 10 years, after Paleo diets started to become popular, scientists have discovered traces of seeds and grains on the teeth of fossilized early humans. They’ve also found remnants of grains on stone cooking tools.
It’s looking like some early humans not only ate grain, but they also were grinding it into a crude flour and cooking that into a primitive form of pita bread.
There’s also good evidence now for a continued evolution in amylase genes. Amylase is an enzyme in our saliva and our small intestine that breaks down starches so we can absorb them. If you look at populations today that eat a lot of starch, they’ve evolved more copies of amylase genes than populations that don’t eat much starch. Extra copies make the digestion of starchy foods even easier.
The moral is that you’re really on shaky ground every time you try to set up a “this is how it was and that’s how we should be” standard. We’re always revising our ideas of what early humans were like, and that is a worthwhile endeavor. But we shouldn’t do it to find what we’re supposed to emulate.
Q: We’re now learning that our microbiome can affect our health. Has our microbiome changed?
A: We are quite different from our ancestors in our microbiome, the billions of microorganisms that reside on and in us that we didn’t know existed 25 years ago when the Paleo movement began.
Think of yourself as a coat hanger of humanity on which are draped this huge number of microbial cells. The microbiome is a part of who we are and it’s essential for our normal functioning. But it differs from person to person, from place to place, and probably over time.
We don’t know how much or in what ways our microbiome has changed from that of our ancestors, although we do have a hint that there have been enormous changes. Some of this probably has to do with changes in the atmosphere or diet, not evolution. It’s more evidence that we are not who our ancestors were.
Q: Does Paleo food exist today?
A: Not really. Even if you wanted to try to eat what people were eating a long time ago, the majority of those foods are simply not available. Early humans were not eating plants or animals that resembled very closely the plants or animals that we eat today.
Human beings have been influencing the foods they eat ever since there were people. For example, the ancestors of apples were nasty, horrible, little tiny bitter things that, really, why would one eat them?
The ancestor of corn that was used by peoples in the Americas for quite a long time was called teosinte. It looked like the head of a grass seed, which it basically was, and nothing like what people eat now.
The meat in the supermarket, even grass-fed beef, has also been modified from its ancestors by breeding. People underestimate the degree to which human beings have affected everything in their environment.
Q: Don’t some people say that they feel healthier eating a Paleo diet?
A: I’m not arguing with people who say, “I started eating this way and I feel great.” More power to you. But it’s also perfectly possible that people who eat in a variety of other ways, as long as they’re not subsisting on Coke and Cheetos, would be healthy as well.
The way to find that out is not to look more closely at what early people were supposedly eating. It’s to gather evidence about who we are now.
Q: S. Boyd Eaton, the Emory University professor who co-wrote The Paleolithic Prescription in 1988, which helped start the Paleo movement, says that he eats a “soft version” of the Paleolithic diet, which includes whole grains, low-fat dairy foods, and wine. Those are foods that are usually forbidden on a strict Paleo diet.
A: That’s exactly the point. You can call the diet Paleo, but let’s take as an inspiration what we think was a healthy way to live and then figure out which aspects of the diet make the most sense, relying on science, not on an idealized version of our earlier selves, for the answers.