Every now and then, I come across articles that criticize the Paleolithic diet. The majority of these articles are so poorly researched and full of errors that I don’t bother reading them all the way through; I quickly close the browser tab and move on to something better. However, occasionally I stumble upon articles that are written by educated people and have been published on sites that tend to maintain a high standard with regards to the scientific accuracy of its content.
For example, two days ago, I came across an article entitled The “True” Human Diet, written by paleoanthropologist Peter Ungar and published on the site Scientific America. Mister Ungar makes the claim that the Paleo diet concept lacks a solid foundation of anthropological data to stand on. He argues that our ancestors ate whatever foods they could get a hold of and that cereal grains were a staple component of the diet of at least some preagricultural humans. He then proceeds to finish off his very short critique of the Paleo diet by saying that we humans are extremely flexible with regards to the types of diets we can sustain ourselves on and that it makes little sense for contemporary people to try to emulate the diet of ancient hominins, seeing as there was no one diet consumed by all Paleolithic humans.
In today’s article, I thought I’d briefly explain why I don’t find these types of arguments convincing.
Are cereal grains “Paleo”?
The arguments that Peter Ungar brings up in his Paleo critique are not new; they are included in pretty much every article and presentation that is critical of the Paleolithic diet. What Mister Ungar, as well as many other Paleo critics, fails to recognize is that these arguments by no means invalidate the Paleo diet concept.
I agree with Peter Ungar in that cereal grains were consumed by some Neanderthals and Paleolithic humans. Several studies support this view (1, 2, 3). However, it’s important to point out that the argument that preagricultural humans ate significant quantities of cereal grains is speculative at best. What Peter Ungar fails to mention is that the studies he’s referring to don’t prove that cereal grains were regularly consumed in large quantities by many preagricultural humans; they merely indicate that some ancient hominins likely consumed cereal grains. This is not a new discovery. It’s well established that at least some Paleolithic people may have eaten the seeds of various grasses. However, the weight of the evidence suggests that cereal grains did not make up a significant part of preagricutural human diets, at least not prior to the late Upper Paleolithic, which led over to the Agricultural Revolution (4, 5, 6, 7, 8).
This is important to note, because the Upper Paleolithic (50.000 to 10.000 years ago) accounts for just a very small part of the Paleolithic era (2.6 million YA to 10.000 years ago). Even if grass seeds took hold in the diet of some ancestral populations some millennia earlier than previously thought, it wouldn’t mean that there has been ample time for genetic adaptation to a grain-heavy diet to occur.
The idea that cereal grains made up a large part of the diet of ancient hominins is further refuted by the fact that contemporary hunter-gatherers such as the Hadza, who live in a part of the world that is thought to be the birthplace of humanity, rarely, if ever, eat cereal grains (9, 10). They primarily eat fruits, tubers, meat, and honey. Modern foragers are not a perfect replica of ancient foragers; however, their practices do yield some valuable insights as to how our primal forebears lived. The diet of our preagricultural, African ancestors was probably not that different from the diet of modern, African hunter-gatherers. It wasn’t necessarily identical and would obviously have varied throughout the Paleolithic; however, it was likely similar in several respects, given that many of the same types of food resources that modern groups such as the Hadza exploit were available back in ancient times.
You don’t have to be an expert in evolutionary nutrition to understand why cereal grains aren’t a preferred food group among hunter-gatherers. First of all, it’s very labor intensive to collect and process wild cereals. From the perspective of optimizing the number of calories you get for the amount of work you have to put in, it’s not a good strategy to focus your efforts on collecting cereal grains, unless your access to other food sources is for some reason highly limited. It wasn’t until we humans started domesticating grass seeds that it became feasible to eat a lot of wheat, barley, and other cereals.
Second, it’s important to point out that it wasn’t until quite recently – on an evolutionary time scale – that we humans understood how to control fire. It’s impossible to say exactly when our ancestors learned how to make fire (different dates can be implied from different studies); however, what can be said with a high degree of certainty is that a widespread ability to control fire at will probably didn’t emerge until the later stages of the Paleolithic era, perhaps one or a couple of hundred thousand years ago. Cereal grains such as wheat are of course inedible in their raw state and would therefore not have been a part of the diet of ancient hominins who didn’t know how to make fire.
Even when our ancestors got the hang of cooking, they couldn’t just go down to a supermarket, buy a container of oats, and boil themselves some nice, warm porridge; they would have had to go through the labor intensive process of collecting grass seeds and then overcome the obstacle of creating jars or other tools that allowed them to effectively heat the cereals they had collected.
All of this is not to say that I think that it’s unwise to eat cooked foods. Cooked food is – and has been for a long time – an important part of the diet of Homo sapiens, which emerged about 200.000 years ago in Africa. All I’m saying is that we have to consider our evolutionary history with regards to the production of fire when we consider what types of foods our ancestors consumed.
A third and very important thing I’d like to point out is that a large body of evidence suggests that the introduction of cereal grains into the human diet adversely affected human health (e.g., oral health, bone density) (3, 4, 5, 11). This isn’t surprising, given that cereal grains have several nutritional characteristics that make them “inferior” to the types of foods that were regularly consumed by preagricultural humans. These facts alone should make us think twice before making grains a staple component of our diet. Furthermore, the fact that there is a marked difference in the nutritional stress imposed upon the skeletons and teeth of hunter-gatherers and early farmers further refutes the idea that the change to a more cereal-based diet occurred long before the Agricultural Revolution.
Here’s what a 2013 review paper had to say about this matter:
The composition of oral microbiota underwent a distinct shift with the introduction of farming in the early Neolithic, with the earlier hunter-gatherer groups displaying fewer caries- and periodontal disease-associated taxa. This is consistent with skeletal evidence showing marked increases in periodontal disease following the transition to an agricultural diet, suggesting a major impact on the human oral ecosystem around this time. This is thought to be caused by increased amounts of soft carbohydrate foods compared with hunter-gatherer diets. (8)
A recent study found that the prevalence of dental caries is quite among the Hadza hunter-gatherers (12), which isn’t really surprising, as they eat a lot of honey, as well as starchy foods. While the findings of this study are interesting, they can’t necessarily be extrapolated to ancient hunter-gatherers, for a number of reasons. First of all, as pointed out earlier, the diet of modern hunter-gatherers isn’t necessarily identical to the diet consumed by preagricultural hunter-gatherers. The Hadza eat an enormous amount of honey, particularly during certain parts of the year. The typical Paleolithic, African hunter-gatherer may not have eaten as much honey as the Hadza man. Second, a solid body of evidence indicates that the Agricultural Revolution was accompanied by a marked decline in the oral health of Homo sapiens (4, 5, 8, 13).
Most Paleo critics fail to see the forest for the trees
Okay, let’s now move on to the second argument that Peter Ungar makes in his article, namely that our ancestors ate many different types of diets and that it therefore doesn’t exist such a thing as the Paleo diet. Like many other Paleo critics, he seems to operate under the belief that many of the scientists and health practitioners who support the ancestral nutrition concept think that there was just one Paleolithic diet. This is not the case. No sane person has ever claimed that all Paleolithic humans ate an identical diet.
You don’t have to have a PhD in anthropology to understand that the types of foods that were available to ancestral humans differed depending on climate, season, and geographic locale. A group of Paleolithic hominins who had travelled out of Africa and settled down in a different and colder part of the world would obviously have eaten a different diet than those who stayed put on the African continent. And even among those bands that lived on the same continent, there would probably have been a lot of inter-group variability with regards to diet composition.
What a lot of Paleo critics seem to have trouble understanding is that the fact that hunter-gatherers – both ancient and modern – aren’t a homogenous group with regards to the type of diet they eat by no means invalidates the evolutionary nutrition concept. The scientists and health practitioners who’ve spearheaded the research on evolutionary nutrition are all perfectly aware of this fact.
Only someone who doesn’t know much about nutrition would make the argument that there’s no point in trying to emulate the diet of our ancient ancestors, seeing as they ate a great variety of different foods, depending on where in the world they live.
The fact is that all hunter-gatherer diets have a set of similar characteristics that link them together and separate them from other diets. Among other things, virtually all of the foods that are included in all hunter-gatherer diets have a high satiety index score, low carbohydrate density, low-moderate glycemic index, and low-moderate energy density. Moreover, hunter-gatherer diets don’t contain dairy foods or cereal grains (except sometimes in small quantities), and tend to be high in fiber, antioxidants, protein, and omega-3 and low in omega-6, sugar, antinutrients, starch, and saturated fat (14, 15).
This is particularly true if they are compared against modern Western diets; however, even when they are compared to other prudent diets, hunter-gatherer diets come out “on top” with regards to their nutritional characteristics. For example, when compared to Mediterranean diets, hunter-gatherer diets tend to have a lower carbohydrate density, something that is favorable with regards to the impact on the oral microbiota, among other things, and contain fewer antinutrients and other potentially problematic compounds. It’s important to be aware of these facts, because the impact a diet has on gene expression, sleep quality, immunity, gut microbiota composition, and hormones largely depends on its nutritional characteristics.
Peter Ungar seems to be largely unaware of these things, which isn’t surprising, given that he to my knowledge has no formal training in nutrition. It took me almost 10 years of research to “decipher” the Paleolithic diet – and still, there’s a lot I have yet to discover. You don’t understand evolutionary nutrition over night.
Given that Peter Ungar’s knowledge about dietetics is limited, I would argue that he shouldn’t be so vocal with his opinions about the Paleo diet. In his article, he points out that he’s not a dietitian and that he therefore can’t speak with authority about the pros and cons of the Paleolithic diet; however, it clearly shines through that he doesn’t think very highly of the Paleo diet concept (I suspect he’s a little biased by his love for pizza, French fries, and ice cream).
Peter Ungar undoubtedly knows a lot about paleoanthropology and he’s also done a lot of work related to the evolution of the human diet; however, he doesn’t seem to be well-versed in nutritional science or have a thorough understanding of how different diets impact the biological system that is the human body. If he had, he probably wouldn’t be so skeptical of the Paleo diet concept.
Another thing that seems to elude him, as well as many other critics of the Paleo diet, is that the diets of modern hunter-gatherers that live in habitats that differ markedly from the African one are not a good representation of the types of diets that conditioned the human genetic make-up over million of years. It’s not that relevant what the Inuit or another group of foragers that live in a remote area of the world eat. It’s a lot more relevant what African hunter-gatherers – both ancient and contemporary – eat, as Africa is where most of our genus’ evolutionary history took place.
With all of that being said, I want to point out that I have no quarrels with Peter Ungar personally. From what I can gather, he’s very knowledgeable about the evolution of man and has done a lot of good work in the context of evolutionary nutrition. I respect him and the work he’s done. Also, I think it’s important to discuss the things he brings up in his critique of the Paleo diet.
We should let the data speak for itself
Loren Cordain, one of the founding fathers of the Paleo diet movement, has said many times that we should “let the data speak for itself”. I couldn’t agree more. I’m completely open to debating the validity of the Paleo diet concept. I don’t have a horse in the diet race. I don’t sell Paleo books or primal cookies or do paid endorsements for manufacturers of these types of products. My goal is not to defend the Paleolithic diet at any cost, but rather to get at the truth.
The reason I’m a proponent of the Paleolithic diet is simply that it is a very healthy diet that is built on a solid foundation of scientific data. The original human diet is not the optimal diet for everyone; however, it’s undoubtedly a good starting point for creating a healthy diet.
I welcome debate; however, I’m not open to debating with just anyone. There’s no point in trying to argue with someone who hasn’t taken the time to read up on evolutionary nutrition and is fighting against straw men. Some people base their opinion of the Paleoltihic diet on what they’ve read in the press or a single study or presentation they’ve seen. These people don’t possess all the information they need to make sense of the ancestral diet concept. I would argue that our beliefs should be shaped by science and thoughtful discussion, not by popular opinion or the statements of one or a couple of health & fitness gurus.
Furthermore, we have to look at the totality of the evidence. The people who bash the Paleo diet don’t do this. For example, in the case of cereal grains, they typically find one or a couple of studies that indicate that cereal grains may have been a part of the diet of some Paleolithic hunter-gatherers and/or that antinutrients such as wheat germ agglutinin aren’t as harmful as the proponents of the original human diet claim they are, and then use those studies to make the case that the Paleo diet concept lacks merit. Basically what they’re doing is cherry-picking data that support their opinions and beliefs (and also often distorting the data so they better fit with their opinions), as opposed to looking at the totality of the evidence. This is a perfect example of scienitis in action. Not all Paleo critics adhere to this approach, but unfortunately, many do. Perhaps needless to say, it’s equally bad if proponents of the evolutionary nutrition concept do this. We should all strive to maintain a high standard with respects to the scientific accuracy of our arguments.