Our ancestors did not eat a Paleolithic diet

For New Year’s Day, I’m republishing the top 10 articles I wrote in 2013. Well, actually top 9, plus 1 from 2012 that just keeps going.

#4. This article was published on 22 July 2013, and has had nearly 12000 views. Another fad diet with little scientific support, and only anecdotal evidence that it might work. 

Surprisingly, most of the questions I get through emails about “skepticism” ask about the science or myths in popular diet fads. It’s clear that there are a lot of websites, pundits, and websites with pundits who think that changing your diet is the most important thing in the world. Eat this to make your immune system strong. Don’t eat that because it causes cancer. But do eat this because it reduces your risk of cancer. Eat this. Don’t eat that. Drink this. Eat more of that. 

My thoughts have always been that the human physiology is amazingly resilient, and as long as you have no chronic diseases, there is nothing one can do that will make the situation much better or much worse. Yes, maintaining levels of certain nutrients, such as vitamins C and D, iron, and others, are critical, but in the modern world, it’s almost impossible to miss out on those micronutrients. Yes, we should limit fats and “sugars”. But the thing is human physiology is complex, so marathoners eat lots of carbohydrates, and they are mostly healthy. It all depends.

And as I’ve mentioned, you’re not going to prevent or cure cancer with supplements (or presumably foods that are rich with those nutrients). Antioxidants don’t really help prevent cancerSoy won’t stop certain types of cancerNor will certain foods make you lose weight. Most of these beliefs about foods, health and weight loss are based on either a boatload of anecdotal evidence, or use very preliminary laboratory research, make a leap of faith, and assume that laboratory evidence is equivalent to clinical evidence. Then, when the gold standard of research, a randomized clinical trial is done, the results generally show nothing. And in some cases, the negative effect is with the supplement or food.

And if you’re looking to try the newest diet craze, be aware that most fad diets just have no long-term successes, and may actually do harm. 


A lot has been written about the diets of our great ape or human ancestors; some of these beliefs about our ancestor’s diet are used to support whatever food craze is trending at the time. Some vegans will claim that humans evolved to be vegetarians, but according to modern scientific research

…since the evolutionary split between hominins and pongids approximately 7 million years ago, the available evidence shows that all species of hominins ate an omnivorous diet composed of minimally processed, wild-plant, and animal foods.

Some vegans, to contradict the lack of evidence that ancient humans, or our ancestors, were 100% vegetarian, will then make a claim that humans “evolved” to be more vegetarian over the past few thousand years as we moved to an agrarian based culture, but that ignores the fact that evolution does not work that quickly on a species that has such a long lifespan and such a low population. There just is no scientific evidence that we evolved to be an exclusively vegetarian species.

On the other hand, there is a current fad for the paleolithic diet, which is based on the supposed ancient human diet of wild plants and animals that various hominid species habitually consumed during the Paleolithic era. It consists mainly of fish, grass-fed pasture raised meats, vegetables, fruit, fungi, roots, and nuts, and excludes grains, legumesdairy products, salt, refined sugar, and processed oils. It really attempts to be scientific (much more so than vegans), but it seems to border on the edge of pseudoscience, and can be considered a vogue diet, without much science backing it. Maybe its a good diet for health (we have no real evidence supporting it), but is there any evidence that our paleolithic ancestor actually ate a paleolithic diet? 

Clearly, real science can provide us with strong clues and evidence as to the sources and quality of foods eaten by ancient humans (and their relatives). It is fairly straightforward to determine what our ancestors might have consumed, just based on a quirk of plant photosynthesis. First, we need to provide a bit of a chemistry lesson. Carbon, the so called building block of life, has two stable isotopes: carbon-12 (12C) and carbon-13 (13C). Around 98.9% of naturally occurring carbon on Earth is 12C (which has six protons and six electrons). 13C, which comprises about 1.1% of the planet’s carbon, has six protons and seven neutrons. Both types of carbon exist in every biomolecule, and as far as we know, the human physiology is incapable of selecting one type of stable carbon over the other. (I don’t want to look, but I bet someone out there is pushing a carbon-13 diet, because it’s better.)

Stable isotope analysis can measure the 12C/13C ratio, which is useful because different organisms have different ratios depending on what organisms they ingest. Importantly, plants have different ratios based on the type of photosynthesis they use to fix CO2. Plants that use C3 photosynthesis (mostly trees, shrubs and herbs) don’t select for one type of stable carbon over the other, so the 12C/13C ratio in these plants is the same as the ratio of carbons in the natural environment. However, plants that rely on C4/CAM photosynthesis (including tropical grasses and sedges, such as corn and sorghum) are much more selective toward 13C. Since animals build molecules in their bodies from the foods they eat, analyzing the stable isotopes of fossilized remains can tell scientists a lot about an ancient organism’s diet. Furthermore, the 12C/13C ratio in fossilized remains represents the type of diet over a lifetime, rather than from one meal. Think of the ratio as a measurement of the “average” diet of the organism over its lifetime

An analysis of the 12C/13C ratio in Australopithecus afarensis, a hominin (apes that include humans and their immediate ancestors that split from chimpanzees, about 5.4 and 6.3 million years ago) from the middle Pliocene (3.0 to 3.7 million years ago) showed that it had already shifted to a C4-based diet, that is, it had already made the switch to grains. Another paper showed that hominins made the shift to the C4-based diet around 2.3-1.2 million years ago, which coincided with the retreat of heavily forested areas that were replaced by open savannah. A third study, which analyzed stable isotopes to investigate the diet of several species of Theropithecus, the ancestors of the modern gelada baboon (a grass-eating ape that lives in the highlands of Ethiopia). The results showed that Theropithecus species almost exclusively ate C4 plants, similar to the diets of the modern gelada baboons. 

In a recently published review article, the authors hypothesized that large brains and upright walking are two of the main factors that distinguish humans from other primates. However, a third significant factor in distinguishing humans from other apes may be a shift in diet from leaves to grasses. As ancient hominims left the forests and ventured into new habitats such as grasslands, they had access to more diverse food sources than found in forests (where most primates have stayed). Researchers are just beginning to understand what ancient humans ate, and these recent studies show that grasses and grains have been part of the human diet for millions of years.

Coincidentally, in a recent article in Scientific American researchers described how chimpanzees eat in the wild. As a bit of background, chimps and bonobos (subtribe Panina), diverged from the line that lead to humans about 5-6 million years ago, and also shares about 97% of genetic material with humans. So they can be used as a proxy to human dietary preferences in the wild, though with a few million years of intervening evolution, including the move to the grasslands. But they can be a “crude measure” of our ancient diets, prior to the move to a C4-based diet.

study by David Watts of the chimpanzee diet in the Kibale National Park in Uganda provided some detailed analysis of their diet in the wild:

  1. Diversity—The Kibale chimpanzees  consumed around 102 species (and possibly many more) of plants either in the form of fruit or leaves. I don’t mean to be picky, but how many species of plants are in your local Whole Foods? And 20 different varieties of apples is still one species of apple. Human ancestors, in a planet with limited food resources, probably were just as fungible with their choices in plant foods as chimps. Modern humans just aren’t.
  2. Figs—Nearly half of all of the food consumed by chimps appears to be one or another kind of fig, fruit of the Ficus trees. Fig trees produce large amounts of fruit that are favored by a number of animals including most primates (including gorillas and many human cultures) and fruit bats. They are highly nutritious and contain a lot of energy, and have a wide number of ecological niches so that it would be distributed throughout the chimpanzee habitat. Early humans would have also found figs throughout their habitats in Africa, and figs were domesticated about 10,000 years ago, and have been a significant part of human agriculture in certain societies. It’s clear that along with increasing the number of plant varieties in our diet, we need to seriously increase the quantities of figs.
  3. Clumps—Chimps eat a wide variety of fruit throughout the year, but only eat one or two species of fruit at one time. So they might eat apples one day then oranges the next. So, they may eat what is “in season” or what is available. Many plants fruit seasonally, or even just for a few days, so the chimps eat what is available. There are a few continually fruiting plants, but they are rare, even in the tropics, so the chimps choose what is available.
  4. Meat–Although we focused on fruits and plant foods, chimps do eat meat, and are considered omnivores, just like their closely related cousins, humans. Chimps favor eating seven kinds of primates, including their favorite, red colobus monkeys along with three other mammal species. However, only 3% of the average chimp diet comes from meat. Given the availability of high energy plant foods, the energy expenditure required to acquire mammalian food probably is too high unless it’s easily obtained.
  5. Variety—One of the myths of our ancestral diets is that our ancestors ate some imagined ideal diet for their bodies. The observation of the chimp diet is that there isn’t an ideal diet, and they eat what they find. Even though figs are a significant portion of their diet, when they find no figs, they don’t eat figs, and change to something else. Some chimps eat more mammal meat than others, if that meat is available, not because of some evolutionary advantage to do so. The authors determined that although some species must eat a specific mix of foods to survive; chimps (and man) are not one of those species.
  6. Termites and ants (and their chitin)—Some chimps are good at eating termites, honey bees and driver ants. It’s unclear if chimps have any special ability to digest the chitin (exoskeleton of insects), but insects do have a lot of energy content. Again, chimps seem to have a broad choice in foods, and eat almost anything that is available. 
  7. Other–Chimps at Kibale ate dirt. Gorillas eat wood and the occasional stone. What we might assume is not food seems to be food for the apes of the Kibale National Park. So, if you want to have an ancestral diet, apparently you have to open your mind to food sources that aren’t just plants and animals.

Before we head to the conclusions from this article, one thing is important-figs. Really, we almost have to wonder if primates would not have evolved without figs. That fruit is a critically important part of the chimpanzee diet, and, given the ubiquity of the plant, we must presume that it was also critical to early Hominims that evolved into modern humans. Figs were domesticated for agriculture fairly early in modern human history, so it must have some importance.

The article makes a cogent argument against making any conclusion about what the “ancestral diet” might have been:

…and that eating some ancestral diet on its own will not make us healthy. Our ancestors did not eat diets perfectly in tune with their body. Rather, they took the best advantage of the foods around them they could in light of their bodies which, like ours, were whittled by evolution out of more ancient forms and so flawed, complicated, and filled with tradeoffs. 

The paleolithic diet itself probably has no more validity than any other diet (lots of anecdotal evidence of success, and no actual scientific clinical studies). The problem is that there is little evidence  that ancient humans, hominins and other great apes ate a particular diet. Clearly, their diet probably was in response to a huge  seasonal, annual and longer duration environmental variability in food sources. Keep in mind that we haven’t even considered the difference in food sources over the planet from Arctic tundra to deserts. But more than anything, is there any evidence that paleolithic humans lived longer or healthier than modern humans? Well, actually the Paleolithic lifespan was around 33 years, whereas modern man is around 67 years (varying from country to country). In other words, despite what many consider to be a terrible modern diet, we’re living longer (which is a result of a lot of things including hygiene, sanitation, medicines, vaccinations, and probably, better nutrition). 

So while there remains little doubt that many modern humans eat too much sugar and processed foods, the studies presented in this article provide strong evidence that it’s impossible to define a “paleo diet”, that our ancestors shifted to grains (a no-no in the paleo diet faith) millions of years ago, and humans are intelligent, so obtained whatever food sources were handily available. Our bodies are what they are, thanks to millions of years of evolution. There is little you can do to your body with food (except for those figs, I suppose), so you take advantage of what food is available to you. You’re not going to live longer if you eat something or another. You’re not going to prevent or cure cancer. Don’t eat more than you burn is about the best advice you’re going to get. 

Whether a “paleo diet” can cause you to lose weight or can provide better nutrition is another topic of discussion for another time. But if you think that a paleo diet represents some idealized diet of our evolutionary ancestors, it doesn’t. It’s an invented diet (again, irrespective of it’s actual clinical usefulness), and imparting some greater characteristic than that is not very scientific.

Key citations

  • newy219 .

    No evidence for the paleo diet? I laughed when I read that then stopped reading the rest of the article.

  • David John Caldicott

    I have a few issues with this article.
    1. You talk about the diet as if the proponents claim it to be a perfect single diet of our ancestors, which isn’t really what it is claimed to be. The idea seems to be that our bodies evolved around the foods that were available to us and that the bulk of that evolution took place long before the modern age. Just because some in the Paleo community might get it wrong every now and again, e.g. thinking grains had no part in our diet until the agricultural revolution around 12,000 years ago, doesn’t mean that the desire to move towards more ‘primitive’ diets is nullified. The fact that early humans may have eaten some grains is one thing, but modern humans eating pounds of the stuff (artificially selected for better taste etc) every day is a totally different kettle of fish. The motivation to adopt the diet is to reduce as many of the potential risks involved with the high sugar diet you already concede is an issue. The reason we have to brush our teeth is because we eat so much sugar, perhaps if we ate more like our flossing-free forefathers we wouldn’t need to waste so much time brushing everyday… same applies with cancer rates, mood disorders and other modern-world plagues that seem to be non-existent in the tribal cultures that still exist.
    2. You talk about variety being important in our ancestors’ diets. How many modern humans eat a varied diet? As we have a food industry that is dominated by sugar, corn and wheat how many of the off-the-shelf products contain food sources other than those big players? For the average person dealing with the challenges of life, deciding what food to eat every day is rarely more complicated then asking “What’s available” and “What do I know I like”. Your idealised view of ‘don’t eat more than you burn’ has no reference to the variety that earlier you demonstrated is clearly important. I’m not a no-grains-at-all-oh-my-god-if-you-eat-grains-you’ll-die kind of person, I just want to make sure that the calories I’m eating come from a variety of foods… and if 50% of my diet is to be from one source I’d rather it be figs than gluten.
    3. Last one, this really gets on my nerves when people refer to ‘lifespan’ incorrectly. The figure you talk about is life expectancy AT BIRTH, which is very different to life expectancy AT ADULTHOOD. Early human children didn’t die from cancers, tooth decay or any of the other food-related illnesses that Paleo dieters are trying to avoid. They died from infections, viruses or being killed by a predator. If you made it to adulthood then chances are you would live well past your 50s, as is seen all over the world in tribal groups that have diets similar to Paleo. So the idea that early human diets were no better for living longer than ours today is ridiculous if your only argument is a misrepresentation of a life expectancy statistic. It’s time we stopped saying ‘people used to rarely make it past 30′ when it is factually incorrect! More accurate would be ‘Babies used to rarely make it past childhood, bringing the average life expectancy at birth to 30 years, but those that made it through childhood lived about as long as we do now.’
    Conclusion – The human condition is very complicated and uncertain, but dismissing something based on a lack of evidence will stifle innovation in actually finding the evidence. Yes, don’t commit 100% to a new fad diet until there’s a few years of research under the belt. But don’t dismiss it and say ‘just burn more than you eat’… that helps no one. I understand your desire to be the skeptical voice of reason, but you can’t be that voice if you don’t give a topic it’s dues. Thank you for giving me something to think about.

  • http://zenpaleoliving.wordpress.com Pepper Culpepper

    Life expectancy prior to the invention of agriculture was quite different from many of the estimates currently bandied about on the Internet. The perception that Paleo-people lived to only about 30 years of age seems to be rooted in the assessment of skeletal remains from that period. However, that falls well short of published estimates based on these data. Further, we have relatively few human bones from the period because it takes some very unusual conditions to preserve human remains for more than 10,000 years. Thus, it is more than a small leap of faith to suggest that these remains are representative of the entire human population at that time.

    The examination of these pre-agricultural bones is further clouded by one of the most important assumptions that underlies these age-at-death estimates. These determinations are made by comparisons with contemporary bones where the age of death of the individual is more easily ascertained. This process for estimating the age of a person’s death from skeletal remains, of course, assumes that contemporary dietary habits, exposure to sunlight, vitamin D status, physical conditioning, and general lifeways were approximately equivalent for the Paleo-people whose remains have survived for us to study. In light of these factors, there can be little doubt that such estimates are little more than educated guesses, yet many of such estimates for remains from the Paleolithic place the age at death at about 40 years (1). This constitutes a much more realistic estimate. However, for many reasons, these are also likely to be underestimates.

    Further, given current sedentary lifestyles, questionable dietary habits, extensive use of sun screen, and that we live out most of our lives sheltered from the sun, it is not reasonable to expect our bones to be as healthy as those of our pre-agricultural ancestors. Thus, estimates based on such comparisons are likely to grossly underestimate the age at death of skeletal remains of Paleo-people. Perhaps the most compelling evidence against assertions of 30 year life spans for pre-agricultural humans lies in human population expansion, spread, and reproductive cycles.

    Humanity, as opposed to the other primates, has spread to all habitable corners of the world. Some scientists believe that the human drift out of Africa took place something less than 100,000 years ago (2). We populated Australia, New Zealand, many Pacific islands, Asia, Europe, and all of the Americas. Current estimates suggest a world population of about 3 million at 35,000 B.C. (3). By the time agriculture was getting started in the Fertile Crescent, our numbers had increased to an estimated 10 to 15 million (4). In the space of 25,000 years, or about a thousand generations, with human populations spread over vast distances, our population increased by 3 to 5 fold.

    The rest of the artilcle is here: http://paleodiet.com/life-expectancy.htm

    Life Expectancy in the Paleolithic
    By Ron Hoggan, Ed. D.

  • http://zenpaleoliving.wordpress.com Pepper Culpepper

    In the face of contradictory evidence: report of the Dietary Guidelines for Americans Committee.

    Hite AH1, Feinman RD, Guzman GE, Satin M, Schoenfeld PA, Wood RJ.

    Author information


    Concerns that were raised with the first dietary recommendations 30 y ago have yet to be adequately addressed. The initial Dietary Goals for Americans (1977) proposed increases in carbohydrate intake and decreases in fat, saturated fat, cholesterol, and salt consumption that are carried further in the 2010 Dietary Guidelines Advisory Committee (DGAC) Report. Important aspects of these recommendations remain unproven, yet a dietary shift in this direction has already taken place even as overweight/obesity and diabetes have increased. Although appealing to an evidence-based methodology, the DGAC Report demonstrates several critical weaknesses, including use of an incomplete body of relevant science; inaccurately representing, interpreting, or summarizing the literature; and drawing conclusions and/or making recommendations that do not reflect the limitations or controversies in the science. An objective assessment of evidence in the DGAC Report does not suggest a conclusive proscription against low-carbohydrate diets. The DGAC Report does not provide sufficient evidence to conclude that increases in whole grain and fiber and decreases in dietary saturated fat, salt, and animal protein will lead to positive health outcomes. Lack of supporting evidence limits the value of the proposed recommendations as guidance for consumers or as the basis for public health policy. It is time to reexamine how US dietary guidelines are created and ask whether the current process is still appropriate for our needs.


    • http://zenpaleoliving.wordpress.com Pepper Culpepper

      Great points. People are quick to attempt to “debunk” the Paleo diet as a “fad” which they believe is “unhealthy” because it contains saturated fat and animal products. The problem is that a majority of people have no clue that the low-fat trend did nothing to lower incidences of CVD and obesity. Not to mention that a low-fat diet promotes mostly processed, sugar laden, chemical lade things that our bodies are not equipped to deal with. The authors premise that “our bodies are resilient” is not based in solid understanding of evolutionary biology. If we are so resilient, then why are Americans plagued with Diabeties, CVD, Obesity? Our children are fatter than ever and riddled with mental health problems. That does not support the author’s claim that humans are “resilient” one bit.

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