Straw ManI haven’t been using the word “Paleo” in my work as often as I once did. Podcast listeners will know that this is because nobody owns paleo and it couldn’t be kept safe from the money grubbers looking to cash in on the movement.  Too many pre-release cookbooks have shown up at my door full of cookies and brownies, and we can no longer simply say “paleo” to the uninformed, trusting that they will only find good information when they look.  Now, I’m forced to say, “I recommend paleo, but not the kind you see all over the internet.”  This only necessitates a half hour discourse on what paleo is and isn’t.

However, none of this is to say that I have in any way turned my back on the concept that human health should be based on evolutionary biology. My desire to not confuse anyone with terms that have become a bit convoluted should not be misconstrued as a change of heart.  The selective pressures that drove our evolution MUST be factored into any plan that intends to make us healthier.

One particular argument against the ancestral diets drives me batty, and it seems to be a common one lately, even perpetuated by people that otherwise seem to have a firm grip on science. That argument is the one in which paleo detractors claim that human evolution is still moving rapidly and, therefore, our recommendation to avoid modern foods like grains, processed carbohydrates, and vegetable oils is wrong.  These detractors don’t understand evolution.

The studies that will inevitably be rolled out in this argument look like this, and this, and this, and this.  Feel free to read each of those, and there are many more like them, but I will give you the gist as I explain the flaw in using them to argue against paleo.

I don’t know of a single person in the paleo community that has ever claimed that human evolution has stopped. However, almost everyone has said that we have not evolved to eat grains, vegetable oils, and processed carbohydrates.  These are very different statements.  Evolution might (I honestly don’t know) be moving faster in humans than it ever has, but this changes nothing about whether or not we have evolved to eat these modern foods. Why?  Because for evolution to happen, a selective pressure and random mutation must come together to benefit reproductive fitness.  And that’s exactly what we see in each of the above studies.

The ability to digest lactose (with lactase) and starch (with amylase), as well as the ability to survive a particular infectious disease, will absolutely provide reproductive advantage.  If you can get more nutrients from less food, or find nutrition in places where I cannot, you will be more robust and healthy, therefore more likely to attract mates, and this is to say nothing of the free time you will have for mating rituals while I must search for more calories.  If you are healthier than me, it is also more likely that you will be more fertile than me, making reproduction more likely.  This stuff is evolution 101.

Let’s use lactose tolerance as an example, since it’s one of the things the detractors try to use against us.  Pretend that you live 6,000 years ago in an agrarian culture (dependent on agriculture) and your people have not hunted and gathered for the majority of your food in generations.  You grow crops and herd animals.  Then, one year you enter a nasty drought that lasts for a long time.  You can’t just pick up and move away like you could when you were a hunter/gatherer.  Your crops are failing and all you have to depend on are your animals as they continue grazing on grass, which seems to be only thing that will grow.  You suddenly find yourself very dependent on your animals for food, including their milk and everything you can make from it.  Now let’s pretend that I am one of your neighbors. You can eat all the dairy you want because you have this brand new mutation in just the right gene and your body kept producing lactase after you stopped drinking your mother’s milk.  I’m not so lucky.  When I consume dairy, I get sick. My belly hurts, I have diarrhea and dehydration, and because I’m forced to eat dairy to survive, my systemic inflammation increases and negatively impacts my fertility.  For you, it’s life as usual.  For me, it’s agony.  If the climate doesn’t improve, and if we can’t beef up the herds enough to accommodate everyone like me with more meat and less dairy, the next generation will be made up of a lot more people like you.  Even more so in the generation after that.  Eventually, in our area, almost everyone will be like you.  That’s the evolution we see in the research.

The paleo/primal/caveman/ancestral community does not argue one word of the above logic.  The stance is that when we eat grains, vegetable oils, and processed carbs, we get sick at 40 and die at 60 instead of 100.  It’s a very rare thing for anyone to eat these problematic modern foods and drop dead in their 20s or get too sick to breed.  If you are following along, it should be clear that anything that kills us at 60 or doesn’t make you sick until middle age does not present an obstacle to reproduction.  If grains, for example, tended to kill humans by the age of 20, anyone still able to eat them today would clearly have evolved to bypass this problem.  But we can eat nothing but grains and drink nothing but Mountain Dew and still have 10 kids before the deleterious effects of our diet finally tear down our health enough to inhibit reproduction.  There’s no line being drawn in the sand that says some genes will go on while others are killed off.  Thus, there will never be evolution when it comes to these modern foods.

The detractors can argue that these foods aren’t actually harmful (a lot of data says otherwise), but they lose credibility when they claim that evolution has already solved the problems we are trying to avoid when we tell people to stop eating these neolithic foods.  There are really only two options here: either they don’t understand evolution, or they are deliberately creating a straw man for some personal gain.  Regardless, knowledge of the basic underlying principles of how we became the creatures we are today will save you from their ridiculous claims.

Go forth and be awesome.

Categories: Nutrition, The Big Picture


  1. You should have Kiefer on the podcast and have a friendly debate. You would win and we’d all learn a bunch from both of you.

  2. Hi Jason, what did you mean by: The studies that will inevitably be rolled out in this argument look like this, and this, and this, and this.

  3. This is strong medicine you write about Mr Seib. You probably should have put a warning at the top. Once you really get how this whole survival/reproductive advantage thing works, there is no going back. You might find yourself looking at EVERY trait we possess and wonder how it gave our ancestors an advantage in getting it on and making babies. I was just thinking about pubes, for example. Why did we keep them and shed most other body hair? Maybe because they were a good repository for pheromones?
    BTW now that I’m finished with my own reproduction and don’t need any more survival advantages, tell me more about those paleo brownies!

  4. Evoluter, visible traits can be a little different because they can also be affected by sexual selection.

    Haha, sorry, I’m not the guy with paleo brownie knowledge. In the rare case that I want a brownie, I just eat a brownie.

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