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Lyle Mcdonald Mercader J. Mozambican grass seed consumption during the middle stone age. Science. (2009) 326(5960):1680-3.
The role of starchy plants in early hominin diets and when the culinary processing of starches began have been difficult to track archaeologically. Seed collecting is conventionally perceived to have been an irrelevant activity among the Pleistocene foragers of southern Africa, on the grounds of both technological difficulty in the processing of grains and the belief that roots, fruits, and nuts, not cereals, were the basis for subsistence for the past 100,000 years and further back in time. A large assemblage of starch granules has been retrieved from the surfaces of Middle Stone Age stone tools from Mozambique, showing that early Homo sapiens relied on grass seeds starting at least 105,000 years ago, including those of sorghum grasses.
My Comments: In recent years, there has been quite an explosion in interest in the supposed diet of our paleolithic ancestors, essentially in an attempt to explain part of why humans are having so much trouble with the modern diet. So far as I can tell the first paper was written in the Mid-80′s or so but even more recently it’s become quite the fad/cult/area of interest for a lot of people.
Now, while an entire article could be written about this, it’s important to note that nobody knows for sure what we ate during our evolution. Even researchers in the field (Cordain and Eaton are two of the major ones) have arrived at rather drastically different conclusions about what our diets contained based on their assumptions because it’s all basically a lot of guesswork. We end up with estimations based on a bunch of assumptions and not much more.
Much of it comes from an analysis of a book called the Ethnographic Atlas, a work done years ago by non-scientists who wrote down (sort-of) what extant non-modernized people were eating. From that, various researchers, making various assumptions about the relative proportions of animal and vegetable foods in the diet have thrown out some ideas about what our evolutionary diet contained. Those researchers have often reached utterly differing ideas based on which built-in assumptions they started with. Other suggestions about our ancestral diet have been made by examining the current intake of extant hunter-gatherer tribes with the implicit assumption that their food intake is representative of our intake during our evolution.
I’d note that it’s unlikely that there was any singular evolutionary diet in the first place. Humans have shown the ability to adjust to all but the most extreme environments and show an amazing ability to adapt to drastically differing diets as well. Human ancestors evolving in say Alaska would have had far different foods available than someone living in the arid plains in Africa. Even examining the extant hunter-gatherer tribes demonstrates this in spades: the diet of an Alaskan Inuit is radically different from say an African Bushman simply due to the difference in environment and what is available to them. So there is no single ancestral diet in terms of the quantities, proportions or types of food that would have been eaten in the first place.
At best we can probably say with some degree of certainty that our ancestors didn’t have many of the foods available to us today. That is, Cap’n Crunch, Ben and Jerry’s Ice Cream and Bud Light weren’t part of our evolutionary diet because they didn’t exist (much to the loss of our ancestors). Beyond that, we can’t say with much certainty what they did eat; it’s mostly guessing because folks weren’t alive to say for sure. And while it may be safe to assume that extant hunter-gatherer tribes are representative, it’s still an assumption.
Now, while there are many different interpretations to the ‘paleo-diet’ craze, at least one thing that most seem to agree on was that refined grains were absolutely not part of the evolutionary diet. Bloggers, apparently unclear on the concept of irony, go on constantly about how ‘Paleo man didn’t have grains, so you shouldn’t eat them.’ Apparently that same logic doesn’t apply to the computers they use to blog with, the Internet that they blog on, their Blackberries that they use to Twitter about their blog updates, modern cars that they use to get to work or the houses they live in. Paleo man didn’t have those either but I don’t see these folks giving those up. Guess they only want to give up the easy stuff when it’s convenient. But I digress.
That is, it’s generally assumed that refined grains (being currently blamed for much of modern health problems) weren’t a major part of our diet until the agricultural revolution, about 10,000 years ago. It’s also assumed that that span of time is insufficient for man to have evolved to deal with them. I’ll only address this second assumption by pointing readers to a new book called The 10,000 Year Explosion: How Civilization Accelerated Human Evolution wherein the authors make a rather good argument that, contrary to common belief, not only did human evolution continue once humans became civilized, that it accelerated.
Rather, in looking at today’s second paper, I want to address that first assumption: that our evolutionary diet was devoid of any type of refined cereal grain. I imagine that, if you’ve read this far, you can guess what I’m going to say about it and what the second study concluded.
The researchers were examining cave artifacts in a cave site in Mozambique which have been dated to somewhere between 42000 and 105,000 years ago. They mention that excavation in 2007 retrieved 555 artifacts. Of those, 70 stone tools were analyzed and were chosen to represent the broadest range of potential plant uses. This includes scrapers, grinders, points, flakes and miscellaneous tools. These were analyzed and while 20% contained no starch residue, the other 80% were found to contain starch granules with the number on each tool ranging from 1 to 650. It’s worth noting that the quantity of granules found on the scrapers was massively larger than what is found naturally in the cave, that is, they were brought into the cave.
The majority of starch granules (89%) were identified as sorghum, a grass showing a large complex of cultivated, wild and weedy types. The researchers note that the starch granules found on the tools analyzed are structurally identical to modern sorghum plants. As the researchers state:
The Mozambican data show that Middle Stone Age groups routinely brought starchy plants to their cave sites and that starch granules go attached to and preserved on stone tools. I cannot prove that starch from all stone tools represents direct tool function…These early grinders are simply modified cobbles and core tools, with a suspected use that conforms to the technological action of “diffuse resting percussion” and “pounding”, which allows the grinding of plant materials.
Put differently, while more research will certainly be needed to verify or refute this claim, data that is a bit more direct than “Assumptions based on a book some guys wrote years and years ago” suggest that as far back as 100,000 years ago, humans had found a way to refine and consume at least some grains for their diet. Or as the researchers state more directly in the abstract above:
A large assembly of starch granules has been retrieved from the surfaces of Middle Stone Age tools from Mozambique, showing that early Homo Sapiens relied on grass seeds starting at least 105,000 years ago, including those of sorghum grasses.
And even if you don’t buy the argument of the book I referenced above, that 10,000 years is more than sufficient to allow adaptation to changes in diet, it would be hard to argue that 105,000 years isn’t time enough to adapt to some degree.
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