Popular diets tout the benefits of going back to the basics. But is the Paleo lifestyle even possible in the modern age?
The supermarket in the after-work rush is quite simply the stuff of nightmares. But however congested the aisles, lengthy the queues, and unhelpful the harried staff, it is also pretty wonderful. At least from a certain historical point of view. Considering that for most of our species’ existence we didn’t enjoy the luxury of having a secure, permanent food source — or any other luxury for that matter, it reflects a major leap forward in our ongoing quest for easy living. What we might also fail to appreciate as we troll the crowded shelves and navigate around half-abandoned carts is that the food we end up selecting was most assuredly not available to early modern humans. And the reverse is also true. That is, our groceries are not stocked with the same fruits, vegetables, and meats our ancestors would have consumed millennia ago. Nevertheless, if the enduring popularity of the Paleo diet reveals anything about our species today, it is that a good number of us is in search of a simpler time when it comes to food — a time when it was a little less complicated and a little less artificial. What that actually means, few seem sure.
What did early humans eat?
Since the publication of the paper “Paleolithic Nutrition: A Consideration of Its Nature and Current Implications” in 1985, there’s been a steadily growing interest in replicating ancestral human diets. Three years ago, one of the authors of that seminal work, S. Boyd Eaton, shared his personal health benefits of following a diet believed to be modeled after that of early humans once inhabiting the African savanna (video). During the same talk, Eaton explained that 30% of their dietary energy would have been drawn from animal protein,* 35% from carbohydrates in the form of fruits, vegetables, and nuts, and 35% from fat. He cautioned that these were rough estimates, but some experts are reluctant to suggest as much.
“We don’t know very much about early modern human diet,” says Amanda Henry, a visiting scientist at the Smithsonian Institution and leader of a Max Planck Independent Research Group on “Plant foods and hominin dietary ecology.” Still, by examining bones, stone tools, and stable isotope ratios, Henry explains, one can make a few general assumptions. For one thing, she tells me, early diets varied significantly from one place to another.
“[O]ur ancestors lived in a variety of different habitats,” she says in an e-mail, “so it’s a mistake to think of the earlier diets as one single consistent thing across all that time and space.”
The “meat myth”
But perhaps the largest unanswered question at the center of this discussion is just how much meat our ancestors actually consumed. Popular belief would dictate that they were a generally hairy, brutish, and carnivorous lot — the last notion being in part propagated by the archaeological record.
“[W]hen we excavate sites from the Paleolithic, we tend to find a lot of animal bones and very little evidence of plants, and that leads to a major problem,” says Christina Warinner, Presidential Research Professor and Assistant Professor of Anthropology at the University of Oklahoma, when we speak via Google Hangout. Plants simply do not preserve as well, she explains, and as a result, many of us — scientists included — embrace what she calls the “meat myth.” “People have made a lot of assumptions about the amount of meat eaten in the past, and it’s true humans have eaten animal products for a very, very long time, but the relative importance of animal products in humans’ diets is very debate-able.”
Even Eaton and his co-author Melvin Konner — essentially the founding fathers of the Paleo movement — confess in the paper that might as well be their constitution, the difficulty of gauging the importance of plants in early human diets.
One of the ways researchers are beginning to reevaluate this question is by examining the plaque left on ancient teeth. Remnants of food trapped in dental plaque reveal that early humans ate a variety of plants, such as seeds of grasses, as well as tubers, Amanda Henry tells me. In a study she led in 2012, she employed the same approach to determine that they also gnawed on tree bark, not unlike chimps and gorillas today. Fortunate for Henry and her research team, the subjects of the study were remarkably well preserved, having slipped into a sinkhole, where they would remain untouched for two million years. And perhaps even more valuable for Henry’s purposes, it would seem oral hygiene had not been a priority for the unlucky souls before they plunged to their deaths.
Fruits and veggies, not what they were
Another one of the few certainties in this inevitably patchy narrative is that the plants early humans consumed were not the same ones we eat today. The fruits and veggies at the grocery store have been cultivated largely for taste and size, and these traits, while appealing, come at a price.
“Cultivated fruits…show a different pattern of sugars than is generally found in wild fruits eaten by free-ranging monkeys and apes,” writes Katherine Milton of the University of California, Berkeley in the journal Nutrition. They might taste better, she continues, as they have been deliberately selected to offer more sucrose and fructose as their sugar reward, but, she cautions, cultivated fruits may also be less nutritious overall and potentially “more demanding” on our bodies.
What’s more, says evolutionary biologist Marlene Zuk, in selecting out for desirable traits, we have significantly limited the number and genetic diversity of our crops, which makes them vulnerable to the perils of disease. To make her point, Zuk alludes to the the Irish Potato Famine.
Could you provide a more modern example, I ask when we speak over phone.
That’s not modern enough for you? she retorts.
Considering what Zuk does for a living, I quickly see her point. And as I do my best to contemplate the entire arc of human history, I consider how late agriculture appears on the scene. A mere 10,000 years ago. It appears so late in our history that many experts wonder to what extent, if any, our bodies have evolved and adapted in response to it.
Have we evolved?
I ask Anne C. Stone, Professor and Director of the Center for Bioarchaeological Research, when we speak via e-mail.
Definitely, she responds. “In particular, agriculture has often altered a population’s consumption of carbohydrates, and this has led to adaptations in our genome.”
One of the most widely cited examples of such genetic shifts is lactase persistence.
“Basically, in two different populations, one in northern Europe and one in northern Africa, different groups of people evolved the ability to digest milk as adults…” Henry tells me. “[T]his gave them access to a brand new source of calories.”
But not everyone has inherited that specific gene and the many other adaptations — and there are, indeed, many. “Seventy percent or so of all humans can’t digest unsoured milk products after early childhood, because most of us are not descended from those dairy farmers,” Konner explains. Likewise, “[b]ecause many of our ancestors did not consume wheat products…many people are intolerant of gluten,” he continues, adding “although probably not as many as think they are.”
These changes are not just occurring in our genes. With advances in DNA sequencing, scientists are finding differences even on the microbial level. In other words, the communities of microbes living in and on our bodies, collectively referred to as the microbiome, are also changing. And again, these differences began cropping up more recently. How recent? Christina Warinner’s research indicates sometime after industrialization — so anywhere in the last several hundred years, which in the span of our species’ history, was basically yesterday.
Are we adapted to modern diets?
But even with these genetic and microbial modifications, the question remains: just how adapted is our biology to the food we eat today?
“[W]e’re probably not adapted to the food that is being sold to us,” Amanda Henry tells me. “The industrialization and consumerization of our food system has led to a lot of things being added to our food that doesn’t belong there or taken away from our food that really should be there.”
In a 2013 TEDTalk that garnered over a million views on YouTube, Warinner illustrated Henry’s point. Holding up a thick stick of sugar cane, she asked her audience to guess how many feet of it early humans would have needed to consume in order to ingest the same amount of sugar found in a liter of soda. The answer: a whopping 8.5 ft. “There’s no physical way a Paleolithic person could have eaten that much sugar cane.”
Echoing Warinner, Konner writes in an e-mail, “There is no way we could have adapted genetically to dietary changes that are only two centuries old at most. That’s why it’s a good rule of thumb to avoid foods that are white, except, for example, cauliflower and fish.”
Ok, got it. No soda. Nothing white. Anything else?
Eat like a monkey
Katherine Milton suggests eating like our closest living relatives — other primates, which feed primarily on plants. For most of humanity, she writes, we were like them, foragers, and we still possess very similar gut anatomy and nutrient requirements. With this in mind, she advises seeking out unprocessed foods, mostly fruits and vegetables, and grass-fed meat over grain-fed.
At the end of the day, says Konner, it is really about the spectrum of nutrients, not one food over another. So, when it comes to deciding on your next meal, maybe ask yourself, “Would a monkey eat this?” and not, “Does it come with fries?”
* In February 2016, S. Boyd Eaton advised that people following a Paleo diet opt for plant protein over that of animal products. Practices involved with raising and feeding beef aren’t sustainable, he reasoned.