Posted by: fireandstone | April 15, 2010

Is Homo Sapien Stuck in a Rut?

I’ve been involved in numerous conversations and debates lately, both online and in the ordinary world, about how much (if any) dietary adaptation has taken place since our early days as modern humans which was roughly some 200,000 years ago. The point of asking is of course to determine whether a natural and proper diet for any given individual is somehow related to their own ancestry, since our species has long since been diverted from our original cradle in eastern and southern Africa. My verdict on the case: yes we are variously adapted and perhaps even significantly. Here’s my argument:

Humans left Africa quite a long time ago. They of course didn’t leave all at once, but left in random groups and in varying directions for various reasons over the course of time. Some groups outside of Africa are almost as old as the human species itself, but major groups had left Africa early enough to make it to China by nearly 70,000 years ago, and to Australia by about 60,000 years ago. Europe was entered by modern humans probably 50,000 years ago and they had completely displaced Neanderthal by 10,000-20,000 years later. For a species that’s estimated to be about 200,000 years old, those are some very significant proportions of time spent in genetic and environmental isolation. It would be silly on just that basis alone to assume that very little to no dietary adaptation has occurred in the same space of time.

The plainly observable adaptive traits among various branches of the human species related to ecological variance presuppose real underlying *physiological* adaptations. The requirement for sunlight induced vitamin D synthesis, which is widely believed to be the selective pressure for skin pigment variation, for instance, doesn’t only effect the superficial aspect but creates a cascade of necessary adaptations one way or the other. The northern dwelling European of bygone eras didn’t simply adapt to make more vitamin D with less sunlight, they needed to go days, weeks and months without the benefit of sunlight altogether, which increased their requirement for purely dietary sources of the vitamin. It’s not wildly speculative to assume that this has resulted in genetic level adaptations related to the *entire* complex of physiological processes that involve vitamin D’s role in the body. Nor would it be wildly speculative to extrapolate the case of vitamin D to any other known and unknown instances of environmental pressures that have shaped modern humans into their many splendored forms.

There is a wide variation in the *observed* dietary habits of healthful modern hunter-gatherers. Much has been made lately about the health and vigor of the Kitavans, a group of modern semi-hunter-gatherer people whose diet is composed by as much as 70% from local carbohydrate sources, and yet seem to show the same resistance to civilization diseases as other HG groups around the world that consume very little in the way of carbs. They are becoming the cult heroes of the carbophile end of the “return to your roots” spectrum in the same way that the Inuit have been the poster culture for the lipophiles. But is this evidence that you can just select any HG peoples’ diet randomly from a hat and just presume to thrive on it regardless of personal relation, or more so that a few isolated groups have simply adapted physiologically out of *necessity* to the unusual conditions of their niche environments? The latter seems entirely more likely, especially given the strength of the clinical evidence that’s emerged to corroborate the insulin cycle model for obesity among westerners. It seems like nonsense to think you could feed the average westerner a diet of 70% yams and get anything other than disaster.

All in all, whether and to what extent our personal ancestry conditions the requirements for *optimal* health and body composition, I will always concede that we can each thrive very well on the diet of our common African ancestors, so when there’s doubt or a lack of inclination to experiment with your nutrition, you can’t go wrong with a prescription to the standard savanna diet of the original human from which we all descended.

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Responses

  1. “For a species that’s estimated to be about 200,000 years old”

    You can’t just use a time frame like this. We are a product of millions of years of evolution. Just because scientists use different labels for different periods of our past ancestors doesn’t mean you can snip off the last one and only use it.

    As you point out the carbiness of the diet isn’t that important. What is important, especially if one wants to avoid cancer, is the elimination of grains from one’s diet.

  2. Well, using a time frame of millions of years is relatively deceptive when taken against the *sum* of the history of our evolution which is some 3.8 billion years. It’s not simply a matter of perspective, but over what time period one could expect to see significant adaptation. 6,000-10,000 years (agriculture and civilization) is unlikely. 50,000-80,000 years (the scope of my discussion) is likely, but debatable. 200,000 years is absolutely certain.

  3. […] that non-superficial variation exists among modern humans, one of those conclusions touching on another post I made recently. I won’t beat that one to death, but suffice it to say that this new […]


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