Not quite paleo

Peter Turchin, advocate of Cliodynamics, has posted on his recent success in adopting the “paleo diet”. The diet is based on the food presumably eaten by our evolutionary ancestors in the Paleolithic era, which is before the dawn of agriculture. Lots of meat, fruit, vegetables and nuts, but no grains.

Although I have much sympathy for the paleo diet for its health benefits (its largely how I eat), I’ve always thought the paleo label was not quite right. Turchin raises this point:

When I explain to friends that I don’t eat any cereals or grains, legumes, or dairy, a frequent reply is – “what’s left?!” Actually, a lot. All kinds of meat, any seafood, eggs, all kinds of fresh vegetables (salad type – lettuce, tomatoes, cukes, radishes, green scallions, cilantro, peppers), other vegetables (all varieties of cabbages, numerous kinds of squash, avocado, olives, asparagus, onions and leaks, spinach), root vegetables (potatoes, yams, carrots, root parsley, yucca, and a number of others I haven’t explored yet), fruits and berries and nuts. No caveman ate the kind of varied diet that we can obtain by an easy trip to the supermarket. So the ‘paleo diet’ is a complete misnomer.

A bigger issue, however, is the evolutionary interpretation of the paleo diet. Evolution is about reproduction, not health. That is why agriculture came to dominate the world despite the initial hit to health that resulted. And even if the paleo diet is the healthiest diet and we are well adapted to it, there is no rule of evolution that says it cannot be improved on. Turchin writes:

Additionally, there is no particular virtue in eating an undomesticated variety, compared to a domesticated one. In particular, I suspect that wild rice is probably worse for you than white rice. Both are grass seeds, and so poisonous by definition. But with the domesticated rice there is at least hope that the most poisonous varieties have been selected out (although it is not a certainty). Interesting how an evolutionary approach makes you look at things from a very different angle.

And this is before we consider recent human evolution – compare the ability to digest grains and alcohol between groups with varying histories of agriculture, and we get very different results. Again, steering clear of rice or grains may be the better health option, but evolution has changed the equation from what it once was.

I prefer the example of tomatoes – sourced from South America, not consumed by out ancestors on the African plains, but they are a core element of many paleo diets. I would suggest the tomato eaters are better off for it. When our hominid ancestors started to eat meat, did a group of them refuse to join in as they preferred to eat the “Pliocene diet”?

3 comments

  1. It’s a heuristic framework for deciding what to shove in your face on a daily basis, not a historical reenactment.

    From an evolutionary standpoint, the second Turchin quote misses the bigger point it implies. Plants — being generally unable to practice fight or flight strategies to thwart predation — must (and do) rely more heavily on chemical defense mechanisms. Wild rice isn’t naturally poisonous because it’s wild, it’s poisonous because it’s a reproductive seed with no claws, fangs, legs, or armor.

    Compare the wild rice example to that of an apple (berry, etc.). Apples have a sugar packed shell which encourages animals to transport its seeds to aid in geographic displacement. Apples ‘want’ to be eaten by large animals. And this strategy provides some symbiosis, as the cyanide-laden seeds tend to pass unharmed through the digestive system of whatever ate it. Calories consumed for big hairy mammal, seeds spread for apple tree. Win-win. If you’ve ever had to clean bird shit off your car, you already get the same point regarding the seeds of smaller fruits.

    Your point about reproduction’s importance is true, yet your example of agricultural crops (historically, grains) aiding reproduction somewhat undermines your “paleo diet folks are using evolution wrong” argument. If the caloric benefit outweighs the cost of the toxicity, there is insufficient selection pressure to drive evolution. Thus it’s possible to get a bunch of humans with low-grade inflammation who are cranking out kids, but are chronically unhealthy at the same time. Grain consumption doesn’t necessarily just cause an “initial hit” that the species adapted to, and now we can all move on. In fact, it’s impossible that that’s true (unless some unknown agricultural bottleneck where our ancestors relied on 9-heart-healthy-whole-grain bread is discovered) at the species level since some cultures transitioned from hunting and gathering to agriculture with rice, some with wheat, some with potatoes, some with maize, et cetera, et cetera.

    I don’t eat tomatoes or the other “new world” gift, potatoes (or corn while we’re at it). That is a decision based on the combination of an archeology class in college and the evolutionary biology underpinnings of paleo, and supplemented by more recent science. Both (particularly before human artificial-selection) contain compounds that are toxic to humans (alkaloids, etc.). Even considering that most of these are broken down by cooking, I think it’s a stretch to say tomatoes are “core element of many paleo diets”. That one seems to be more of an incorrect cultural transmission that tomatoes were sent by God to Italy for the sake of marinara sauce.

    On the most basic level, the evolutionary lens provides actionable answers (with a few seconds of analysis) that Science™ can’t/won’t provide, or that it has been wrong on in the past.

  2. I don’t disagree with much of what you said there, but I have a few thoughts:

    First, I think that paleo as a heuristic versus paleo as a historical re-enactment gets lost for some people. It provides a framework that can be built on. Sometimes it is – whether that is through adoption of cashews from Brazil, macadamias from Australia or tomatoes from the New World (by some, not all). At other times, it is a starting point reinforced by confirmation bias, effectively making it the end point.

    I agree that Turchin’s rice was not a particularly good example, hence my reference to the tomatoes. On that, while “core” might be the wrong word, I surveyed a bunch of paleo sites when I drafted the post and tomatoes are usually on the acceptable list. If you then look at the recipe suggestions, they are full of tomatoes. I’m guessing you are in the minority.

    You miss my evolutionary point slightly (or I didn’t make it very well). What you say about agriculture and whether you are required to adapt applies equally well to previous periods such as the Paleolithic. Just because a diet was broadly consumed by everyone does not mean it is optimal for health – it is optimal for reproduction. You can make an argument that the the long evolutionary history of the paleo diet, coupled with the population structure through that time, makes it likely that we are well adapted to it. But a step beyond the basic evolutionary argument is required. When someone points to a new food – such as tomatoes – the simple “we didn’t eat it” heuristic should be coupled with more serious analysis (which I expect you have done – you probably weren’t the first person I had in mind when I made that argument). Then again, given the way most people eat in the modern world, the “we didn’t eat it” heuristic will probably be a vast improvement for most of them. The tweaking is a bonus.

    Finally, we can see evidence of the mix of forms of agriculture in the evolutionary adaptions that have occurred over the last 10,000 years. Populations exposed to dairy have lactose tolerance. Populations with long histories of grain consumption have lower levels of gluten intolerance (ignoring for the moment the argument about whether gluten is a poison for everyone). Alcohol tolerance in indigenous populations is low. As a result, different populations have different adaptations. But again, as for any period, you might ask if the fact you have an evolutionary history eating it (albeit a few thousand years), or are even adapted to it, makes that diet optimal. I am lactose and gluten tolerant (noting my comment above), coming from a population with a long history of agriculture. But should I base my diet around them? I think the broader evolutionary argument you use around the rice is a nice step up (and rarely made). It’s the evolutionary history of what we eat as well as ourselves that matters.

  3. I think this is a great post, Jason. Like you, I’m largely sympathetic to many of the tenets of the paleo diet. However, I also notice that many paleo diet advocates seem to think that evolution magically stopped right before the dawn of the Agricultural Revolution. In fact, not only has human evolution not stagnated, there is some compelling evidence that it may actually be accelerating.

    If one can tolerate certain foods with no adverse health side effects, then I see no reason to avoid eating them. Just because your distant ancestors didn’t eat or drink something doesn’t mean it’s necessarily bad for your health, nor will it necessarily decrease your lifespan.

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