When Paleo Logic Fails

Terms like “the paleo diet”, “primal lifestyle”, “evolutionary fitness”, and “ancestral health” all operate under the shared premise that our evolutionary past is the key to understanding how to be healthy today.  While I certainly don’t agree with any movement that has one size fits all recommendations, I do agree that this premise is an important place to start from.  However, it can also be a dangerous place to start from because naive reasoning without evidence can easily lead us astray (we all fall victim to this to some degree).  Nonetheless, understanding how and why we evolved the way we did is one key to understanding how we can be healthier and live better today.

I recently finished reading The World Until Yesterday (a book I enjoyed more than I thought I would) which focuses on what we can learn from traditional societies in terms of our health, social relations, conflicts, child-rearing, and treatment of the elderly.  As Diamond puts it in the book: “All human societies have been traditional for far longer than any society has been modern.”  Even though I don’t agree with everything he wrote, I think Diamond makes a compelling case that we can learn from studying our hunter-gatherer ancestors (even though he doesn’t really advocate a paleo diet per se).

This seems like a reasonable starting point and many evolution enthusiasts share this belief.  If one were simply to consider the fact that most of our species’ existence has been spent as hunter-gatherers it would seem that we have much to learn from our ancestors in terms of how to live well, both biologically and culturally.  But is this so, or is this a Paleofantasy? [1]

The first thing to consider is that adaptations (both biological and cultural) don’t necessarily scale linearly.  Just like technological growth, evolution can stagnate for long periods of time, and then quickly accelerate due to selection pressures and for other reasons that are opaque to us.  For example, in just the last 10,000 years things like the ability to tolerate lactose and blue eyes have appeared in the human race.  It also turns out that many people have also developed an ability to eat and properly digest grains (a big no-no paleo diet advocates).  [2]  This evidence, however, doesn’t stop some paleo zealots from proclaiming that evolution cannot occur in such a short period of time.

The paleo diet theory, then, seems to make sense until one examines the evidence.  If human evolution is accelerating, as the evidence shows that it is, then it doesn’t matter how long we ate a “paleo diet” for — what matters is what we have now adapted to eat.  Then again, let’s not rush to dismiss the paleo diet (and its many variations) simply because some populations have adapted to tolerate grains.  Maybe the paleo folks have a point, i.e., just because something is edible it doesn’t necessarily follow that it’s also an optimal (or even good) source of nutrition.

The real issue here is that when you think about it, paleo logic can fail us in terms of how we think about both health and culture (largely due to the narrative fallacy).  This makes any sort of dietary advice very difficult to give because certain populations have adapted to eat certain things that others haven’t.  The implication is, of course, that there is no such thing as a one-size-fits-all optimal diet for everyone.

Paleo Logic is a good a starting point, but when something sounds nice in theory and doesn’t hold up empirically, then I’d suggest ditching the bogus theory.

Notes:

[1] See this excerpt in The Chronicle of Higher Education from a book called Paleofantasy.

[2] See The 10,000 Year Explosion.

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2 Comments on “When Paleo Logic Fails”

  1. Couldn’t agree more that it’s a useful place to start from, but not necessarily the answer to everything. The evolutionary perspective is, I think, a much more valuable lens to begin looking at things through than lots of other options. However, I think lots of people look at evolution and what it’s done to humanity as valuable in what it can tell you *to* do — while in reality, I think the evolutionary lens is more valuable in learning what *not* to do.

    This is, of course, how evolution works. The things that don’t work don’t survive; that’s very clear to see, and we can learn from these types of “failures”. It’s very clear what doesn’t work in evolution, and, as you pointed out, there’s a healthy amount of room for *different* things to work, especially given different populations and environmental conditions. This leaves a whole dimension of experimentation open, which seems to be the core of evolution itself. This is something the strict “paleo” mindset seems to forget.

    In other words, the value of evolutionary perspective is really just the value of “experimental” perspective — find what doesn’t work, cross it off the list, and move on. A lot of the Paleo movement seems to hang on to specific ideas and dogmas, just because ancestors did something similar etc. I think that’s missing the point.

    Great, succinct post!

  2. I was fascinated by the Paleofantasy book, but then the excerpt was chock full of straw-man arguments:

    “Contrary to what the glossy magazines would have us believe, we do not enjoy potato chips because they crunch just like the insects our forebears snacked on. And women don’t go into shoe-shopping frenzies because their prehistoric foremothers gathered resources for their clans.”

    On the other hand, I do actually largely agree with you. I have some issues with Taleb’s (mostly airtight) logic about nature and via negativia but have yet to see if I can formulate it into something more solid.


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