Paleofantasies of the perfect diet – Marlene Zuk in NYTimes


Paleolithic dieter?  Not exactly...

Paleolithic dieter? Not exactly...



Zuk describes how, she was initially enthusiastic about the ‘evolutionary mismatch’ argument around health and diet, but that, upon closer inspection: ‘The notion that there was a time of perfect adaptation, from which we’ve now deviated, is a caricature of the way evolution works.’ Zuk asks which particular stage in hominin evolutionary development was the age at which we were perfectly in harmony with our environment:

How much of the diet during our idyllic hunter-gatherer past was meat, and what kind of plants and animals were used, varied widely in time and space. Inuits had different diets from Australian aboriginals or Neotropical forest dwellers. And we know little about the details of early family structure and other aspects of behavior. So the argument that we are “meant” to eat a certain proportion of meat, say, is highly questionable. Which of our human ancestors are we using as models?

In fact, the idea that our bodies were perfectly suited to a particular environment is an adaptationist fantasy. Processes of evolution, including variation and natural selection, niche creation and co-evolution, even catastrophe and fluctuating rates of evolutionary change, suggest that adaptation is usually imperfect, with abundant glitches that, as long as they don’t constitute abject failures, usually continue to exist unless selection and variation conspire to find a way to get rid of them.

We have never been a seamless match with the environment. Instead, our adaptation is more like a broken zipper, with some teeth that align and others that gape apart. The paleontologist Neal Shubin points out that our inner fish constrains the human body’s performance and health, because adaptations that arose in one environment bedevil us in another. Hiccups, hernias and hemorrhoids are all caused by an imperfect transfer of anatomical technology from our fish ancestors.

I’ve been recently reading a book that I have to review which follows this line of thinking: that evolution shaped us for one sort of environment, but that civilization, technology, social life, and culture all demand something radically different from us, so we’re stuck. There’s an odd inconsistency there: on the one hand, we’re perfectly adapted to paleolithic life; on the other hand, our bodies just can’t get with the last 10,000 or 50,000 years of change. Usually the argument is that ‘we’re just changing too fast now to adapt.’

I think the biological evidence points to the fact that both of these impressions is incorrect, as Zuk suggests: we are neither so perfectly well adapted to foraging (or scavenging or living in trees or whichever stage we develop paleonostalgia for) nor are we so ill-suited for our own environment (in spite of our health problems, we actually live a long time compared to our ancestors, for example).

So before we start waxing nostalgic about all the health benefits of a Pleistocene diet, perhaps we should remember that our ancestors’ food often came in this nasty packaging which tended to run away, attack them, or just go missing entirely when they were really hungry. Zuk’s conclusion is a very balanced one:

This isn’t to say that we wouldn’t be better off eating fewer processed foods. And certainly we have health concerns that never struck our ancestors. But we shouldn’t flagellate ourselves for having modern bodies, and we shouldn’t assume that tweaking our diets or our posture will rescue us from all our current ills. That’s just a paleofantasy about the future.

We are, quite simply, a species of our Age, shaped by the environmental forces around us, just as our ancestors (and us) were also shaped by their Age (whether the Holocene, Pleistocene, or earlier). We drag the history around in our bodies, but we also bear the stamp of our own time, especially in things like diet, as the food choices we make end up affecting the very molecular structure of our bodies and brains. I don’t think we’re fat or have heart disease or live longer because we’re stuck in Stone Age bodies, but rather because we’re fashioning Information Age regimes of food, activity, and environments. We tend to look at our bodies and see their inadequacies, but we could just as easily see them as the perfectly logical products of the developmental processes we create, for all their strengths and weaknesses.

Update: If you still haven’t had enough of discussions about diet and evolution, I’ve put up a brief discussion of Richard Wrangham’s work over at the new site: Food for thought: Cooking in human evolution. And bonus, Prof. Wrangham actually responded to the post and dressed me down for presenting a simplified version of his argument.

30 thoughts on “Paleofantasies of the perfect diet – Marlene Zuk in NYTimes

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  2. This article shows a woeful lack of understanding as to how evolution works and seems to be written by someone to whom science is one big mystery. I am no wiser after reading it as to what the author proposed that I do eat, or why.

    The arguments put forward by Pale Diet proponents such as Loren Cordain are clear and logical – in stark contract to the fuzzy thinking in this article. I just couldn’t be bothered putting up counter arguments; it is nearly midnight here and I don’t want to be up until sunrise.

    Just read Cordain’s book or subscribe to his website. The logic is clear, the only argument is to exactly what foods made up the hunter-gatherer diet, but these are only at the margins. The fact that we evolved for 2 million years on a diet which did not include grains, legumes, dairy products, refined foods or refined sugar is uncontested. The Paleo diet is pretty much what is left over when you take those things out, and make some well educated adjustments in the types of fat we eat – again, based on very clear logic.

  3. Dear Peter —
    Just because something is ‘clear and logical’ does not mean that it is either correct or accurately represents the available data. Much of the data on diet over the course of the last two million years is, in fact, ‘fuzzy.’ It would be great if it were not, but it’s hard to know exactly what was happening in pre-human hominin diet. Even what we thought we did know from evidence of jaw structure and tooth enamel wear turns out not to always be quite so clear.

    For example, there’s some interesting recent research on the robust australopithecenes (sometimes now classified as the genus, Paranthropus) that undermines what we thought about their diet. With huge skeletal structures for anchoring jaw bones and massive molars, the evidence looked conclusive that their diet involved mostly grinding up gritty roots and tubers. But new evidence suggests that they might have eaten a large proportion of fruit, relying on what we thought was their dietary staple in times of stress.

    ‘Clear logic’ in evolution is often adaptationism, the assumption that we are perfectly adapted to our environment or that every human trait is necessarily selected. Increasingly, we’re realizing that’s not the case, that selection works on the whole organism, and because genetic sequences are pleitropic, or expressed in different ways in multiple organs, we’re often not perfectly adapted.

    If Cordain’s diet works for you, great. But that hardly proves its accuracy for describing prehistoric diet, nor does it smooth over the interesting intellectual questions about the role of diet in our development as a species. It’s not ‘fuzzy’ thinking just because it doesn’t provide simple answers.

    For example, one point I made was that much of our ancestors’ meat intake at early stages of hominin evolution was likely not the sort of meat we’d like to eat today. For example, it may have included a lot of small game – lizards, insects, small birds, carrion scavenged off of other animals’ kills – and it’s not clear when cooking came into the equation. We also know that our ancestors had very different tooth wear patterns, and they likely had an interesting array of parasites. Must Paleo diet advocates would NEVER advocate moving to a diet of uncooked small game or carrion — I can’t imagine that book would be a best-seller! But the evidence even from sophisticated contemporary foragers, groups that lived mostly by utilizing food sources occurring without complete domestication, is that they aren’t very squeamish.

    Another issue is something like fiber; odds are that our ancestors got a hell of a lot more of it than we do in refined foods. But there’s a chance that this would mean a LOT of time spent chewing (and a lot of poop, for that matter!). Richard Wrangham, a biological anthropology at Harvard, has done some research on what it’s like to eat a chimpanzee diet, and from his descriptions, I feel for the guy. He says it’s pretty foul: tough, fibrous fruits, some of which are pretty bitter and a few that made him heave. Not only are our jaws inadequate (many of our ancestors’ were quite a bit more substantial) and our guts are just too short and under-strength to get the necessary nutrients out of the food.

    I think it’s great that Cordain recommends eating less high-GI and processed food; hell, I grow some of my own food and eat local here in Australia. But that doesn’t mean it’s a ‘Paleolithic’ diet. That would involve some more radical changes than most of his readers are ready for.

  4. Peter, another thing I feel is worth pointing out is that hominids (especially foraging humans pre-agrarian revolution) DID eat grains. They ate pretty much anything they could get their hands on, and that would have indeed included cereals when in season, and legumes whenever they could have been dug (including cattail tubers). When a population is foraging, they will eat pretty much whatever won’t kill them in an environment. Hell, in South America, foraging populations would even mash toxic potatoes with clay to leach the toxins, and eat them anyway!
    I suppose my point is that humans never had it easy, and while I am totally in favor of eating a more balanced, healthy, high-fiber diet, human life was seldom a matter of wandering about in a huge berry-and-easily-caught-animal-filled garden.

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  6. This is such an enlightening article!

    As far as Peter’s claim that “This article shows a woeful lack of understanding as to how evolution works and seems to be written by someone to whom science is one big mystery,” it is incredibly clear that this statement is utterly, exactly wrong. And I’m incredibly impressed with your response…

    I think your point about the small game issue is a great one. There’s little doubt that various groups of early humans often subsisted on lizards and insects and such, yet I can’t imagine anyone today recommending these as staples in the paleonostalgic diet.

    Kudos on a wonderful article!

  7. Another item on the Palaeo diet would appear to have been other humans – going all the way back to Atapuerca, and at various sites where it has been suggested that human bones appear to have been deliberately smashed in order to extract brains or marrow – I daresay such food would be nutritious, but personally I’d prefer a Mars bar any day of the week.

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  10. Thankfully I don’t have children at University of California Riverside or they may have had the misfortune of having Ms. Zuk as an instructor. Having grown up on a large working farm I don’t think she can grasp the true immensity of how food is gathered in the wild and why we as humans can only truly be healthy eating certain fruits, vegetables, and meats. She’s truly ignorant

    • Insects and lizards may have been on the menu, but because of the shape of our jaws, strength of our bite and corresponding elongation of our skull, it is clear that Cro-Magnon (us) were game meat eaters primarily. Brain development increases exponentially as a species moves away from omnivore behavior and toward carnivore behavior.

      It is simply common sense to assume that if refined grains and dairy have been added to our diets recently, and we recently have a problem with obesity, heart disease, cancer, diabetes and other ailments, that the newest thing added needs to be treated as the culprit.

      Life expectancy, a common argument against paleo diet, ignores one critical factor that any anthropologist will tell you happily. infant/youth mortality is what drives down life expectancy in a population. Humans, even without advanced medicine and hygiene, were as likely to live as long as us if they survived past puberty. Infant mortality has been the single biggest factor in the difference in life expectancy rates between ancient man and us…. as my sister sometimes says, “You just mad ’cause you know it’s bad for you”.

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  13. little d, I suspect hunter-gatherers did eat grains, but only as a very small small part of their diet. Today they’re huge in the modern diet. I have actually tried foraging in a couple of different bio-regions in the Western US, once as a part of a 9 day course in aboriginal living skills. We found no grains, only green leafy plants, berries, certain fruits, roots, grasshoppers, some river-based shellfish, and of course the other animals available to us. (We had little hunting success.) It might have been somewhat different thousands of years ago in a place like the Fertile Crescent, but in much of the world I think grain consumption must have been minimal. That’s the kind of thing I take away from the paleo diet recommendations. There is obviously some latitude as pre-agriclutural people did not all eat exactly the same things. But if you’re eating toast or cereal in the morning and a pasta meal in the evening, I think you’re eating far more grain than we are evolved to handle.

  14. Grains were indeed part of the paleo diet… Usually as sprouts, rarely as dried cereals… And it was considered to be starvation food. The reason our bodies “haven’t learned to adapt” to more modern diets is because they were already adapted to those things…. Increased insulin production, storage as fat and a fast but metabolically expensive bust of energy. Our bodies are doing exactly what they were designed to do and because of the disparagy between our program responses and clever marketing and food product development our bodies are betraying us with a biological gift turned curse.

    I’ve noticed that those who are most vocal in arguing against this science and research are nearly always the ones who are most afraid of having to give up bread, pasta and sugar and high fructose corn syrup… For fear that we are right and risking losing them forever.

    The bright side is that glucose in the blood is the cause of that addiction, and after a week or two, the craving normalizes. You can also “feel ” what the grains and sugars do to you if you consume them after that initial cleansing. It makes it clear in your own mind why paleo man only ate them as last resort food. It hurts the morning after.

  15. I have to agree with Peter. This article shows, at best, a lazy research of what an evolutionary approach to nutrition is really about. Early humans lived in a wide array of ecosystems, so coming up with the exact diet of our ancestors at a given time is evidently very difficult, if not impossible. Had you read more about the Paleo approach (as Peter said, Cordain’s book would be a good place to start), you’d know that it is not about what to eat but what NOT to eat.

  16. The two people to criticize the points made in Greg’s article, of course, have not presented any real evidence to counter his arguments. I don’t understand this. Greg responded eloquently and carefully avoided any derogatory or ad-hominem approaches.

    So, please, as I’m also curious: what exactly did Greg miss in his article? Don’t just say, “read a book,” as that’s not really an argument. “It’s late,” is also not an excuse, as Greg spent his time – which is just as valuable as yours – to actually articulate a response that made sense.

    • Michael —
      Thanks — there’s always a tendency in online discussion for things to get ramped up in intensity, even when it’s sometimes hard to understand why people are even disagreeing with you. But this tendency also bedevils academic arguments, as it can be hard not to respond to what we think we hear, or what in an argument reminds us of a long-standing argument we’re already having.

      As I tried to make clear in my piece, I have no beef with the ‘Paleolithic DIET’ — some of it sounds damn sensible to me: cut waaaaay down on simple carbs, get a lot more fruit, nuts, and organic proteins. Makes bloody good sense to me. My beef is with thinking that this is a) what our Paleolithic ancestors ate (that ate a lot of stuff I suspect most Paleolithic dieters wouldn’t touch, b) that we are perfectly adapted to an imagined diet of around 60kya, and c) that are bodies are ‘designed’ to do anything (they aren’t ‘designed’ — that’s Creationist thinking).

      Our gut is a weird one, as I try to detail in a recent post on our new site at PLoS blogs on Richard Wrangham’s work. We’re just about the only species that I can think of that has made such a rapid evolutionary shift from a vegetarian primate diet (likely heavily frugivore and insectivore, although not entirely clear) to a distinctive omnivore primate diet. So our gut is not ‘perfectly adapted’ to what we’re putting in our mouths; and it can’t be because the variety of our capacity to process food is what made it possible for our species to spread to such a variety of ecological niches. If we were ‘perfectly adapted’ to life on the East African steppes, we wouldn’t have had such success going everywhere from Siberia to the Pacific Islands to Australia to Northern Europe.

      But the key issue of grains is a really interesting one, because humans have really shifted the global environment so that grains (and grasses more generally) are probably more dominant now than any time in our planet’s history (there was a book on the evolutionary history of grass that I’ve wanted to read, but I can’t remember now who the author was). From the point of view of the grass and grain species (if I can say that), they’ve successfully used humans as a reproductive and anti-competitor device to roll back forests, swamps and a whole host of ecosystems to become far more pervasive than they were when our ancestors were foraging.

      That is, our niche modification has meant that, even if you wanted to forage, you’d find that human intervention has shifted the terms of the equation. Paleolithic Dieter in 60kya would have still had megafauna and far more variety of large-bodied edible animals, far less grain in the environment, far more old growth forest, etc.

      So don’t get me wrong: if you’re advocating a good diet, composed of lots of healthy foods and eschewing heavy dependence on simple carbohydrates, more power to you. If you think you’re able to step through a dietary temporal gate and recreate ‘the’ ancestral diet, to which our ancestors were ‘perfectly adapted,’ then you’re justifying good decisions (and perhaps even good dietics) with bad paleoanthropology.

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