Dear Mark: Did Grok Eat Grains?

The Primal Blueprint, as our good readers know, is founded on the principle of evolutionary biology. This certainly applies to our view of what’s appropriate or not in terms of nutrition.  In short, what our long time ancestors ate during the course of 2 million+ years, we’re still designed to eat. Even the last 200,000 years of hunting and gathering, from a physiological standpoint, trumps the comparatively short 10,000 or so years since the Agricultural Revolution, when humans commenced widespread farming practices and prepared grains as a significant part of their diet.

An article published in this month’s Science Magazine presents archeological evidence that, according to its author, challenges this accepted timeline. A number of readers have written me about this story. Here’s one letter among the bunch….


Please help me make some sense to this: Stone Age diet included processed grains

I’m a crossfitter in Colorado and most of the gym keeps a Grok diet and are confused about this article. Does this open the door to other minimally processed grains?

Let me give you the gist. Julio Mercader of the University of Calgary examined a variety of tools (scrapers, grinders, points, flakes, and drills) he and others retrieved from an excavation site in Northwest Mozambique. Based on dating of surrounding sediment layers, Mercader estimated the age of the oldest tools to be approximately 100,000 years old. Some 80% of the tools he found tested positive for sorghum starch residue, which – he says – suggests that sorghum was used as a food source at the time. Other residues found on the tools included African wine palm, African potato, the false banana, pigeon peas, and wild oranges.

Let’s suppose that Mercader’s dating estimates are correct. Let’s also suppose that the tools Mercader tested had indeed been used to prepare food, as the presence of other food residues suggest. First off, it doesn’t necessarily follow that the sorghum was also used as food. Tools, for prehistoric humans (if not for moderns as well) needed to serve multiple purposes, supporting not just food preparation but shelter construction and other daily living tasks. As one archeologist skeptic, Curtis Marean of Arizona State University in Tempe, explains, grasses were regular parts of “bedding” and “kindling.” Another critic, Huw Barton from the University of Leicester, questions Mercader’s assumption that the sorghum had been used for food based on the curious presence of the residue on tools not associated with food preparation, including drills.

However, the biggest stumbling block on the way to Mercader’s theory is sheer inefficiency. Just because evidence exists that they could, doesn’t mean that they did – with any regularity, if at all. I’m with critics of the findings like Marean and Loren Cordain, who argue that the full sequence of finding, collecting, transporting, processing and baking any kind of grain wouldn’t have been worth the effort for the nominal nutritional benefit gained. Make no mistake, the use of grains for food isn’t as simple as pulling and popping the seeds in your mouth. Even if you attempt to harvest the seeds by hand, a “tedious” process as Cordain notes, you’re still looking at a fairly lengthy processing. Raw, fully intact grains are indigestible for humans. The necessary preparation process involves – minimally – roasting (a relatively inadequate option) or fine grinding and baking (a better but more intensive method). Nothing from the excavation site shows any seed gathering tools like “animal skin containers” or baskets/pottery (too early for this time), as Cordain explains. Furthermore, there is nothing present at the site to confirm any kind of cooking preparation. As provocative as it is, it’s scientifically too big of a leap to make with any certitude.

Finally, even if the people of the Ngalue region did actually eat the sorghum as Mercader believes, there’s a big difference between suggesting grains were a significant and regular source of our ancestors’ diet 100,000 years ago and saying they were merely occasional – and probably desperation-induced – fruits of foraging labors. In times of scarcity, pre-Agricultural humans probably resorted to less nutritionally efficient means of “gathering.” It’s called the survival instinct, and it’s of little surprise that they might have been moved to a certain degree of ingenuity when their life depended on it. However, when the group was able to relocate or when traditional foods were in good supply again, logic dictates that they would have returned to their staple diets. The evidence supporting the use of the sorghum for food is relatively scant and virtually nonexistent when it comes to the gathering, processing and preparation of any significant supply. While Mercader’s research promps speculation to what an isolated group of early humans could have attempted on a small and likely very temporary scale, it doesn’t in any way rewrite the historical timeline on agricultural development – or evolutionary nutrition.

You know where I stand on Mercader’s study. I’m interested to hear what you all have to say about it. Shoot me your thoughts, and thanks as always for your great questions and comments. Keep ‘em coming!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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