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Evolution, Anthropology and Human Nutrition

It is clear that humans have only eaten an appreciable amount of the very high-carbohydrate foods (in particular sugar, and ultra-refined grains) for a fairly short time in their overall development. Now before anyone accuses me of being some crazy ‘Paleo guy’ remember that I started consulting in the nutrition field before Paleo was ‘cool’….way back in the late 1990s. But, as a rational scientist it does make sense to me, to look at what humans have eaten over their many tens of thousands of years of development and what the remaining free-living hunter-gatherer populations still eat, to at least provide some extra context to what we should be doing now.

For many thousands of years’ humans survived as hunter-gatherers and it is only in the past several thousand (an evolutionary ‘blink of the eye’) that we have shifted to a diet in which grain-based and high-sugar foods dominate our food supply. It is even more recently that we began to eat the vast amounts of highly processed and ultra-refined foods that now make up the bulk of the modern diet.

The agrarian shift reduced health of our ancestors

At the time of the invention and rapid uptake of agriculture around 10,000 years ago, people’s height decreased and health suffered.1 While we tend to think that having an abundant supply of food would preserve health and performance the opposite appears to have taken place. What it instead provided food security. There are undoubted benefits to this, but the higher-grain diets that became common were not ‘healthier’ by any means than the preceding diet based on a mixture of tubers, leaves, berries, fruits, nuts, seeds, meat and eggs, and lesser amounts of grains and legumes that were able to be foraged and prepared (yes, Palaeolithic man did eat grains and legumes, just not in large amounts). 

At the time of the invention and rapid uptake of agriculture around 10,000 years ago, people’s height decreased and health suffered

A diet based on a few staple crops provides less variety of nutrients than one based on hunted and foraged foods. This had the effect of practically malnourishing people and leaving them more susceptible to diseases that also became more prevalent due to both closer living conditions and zoomorphic infections transmitted by farm animals. While it was previously thought that the shift towards agriculture allowed an increase in population that was at least partially related to improved health, it is now generally recognised that there was a reduction in individual physical health with the abandonment of a hunter-gatherer lifestyle. 

What do extant hunter-gatherers eat?

By looking at remaining (or recently remaining) hunter-gatherer populations, we can see some of the best evidence for not only how humans have eaten over the course of our progression as a species but also how this affects health. Until relatively recently hunter-gatherer groups have subsisted healthily (notwithstanding mortality from infectious diseases, warfare or predation unrelated to diet) with a significant absence of metabolic disorder on a typically lower carbohydrate diet than that promoted recently by government agencies and public health organisations.

The Inuit for example, have by necessity utilised a low-carbohydrate diet for millennia. Their traditional diet contains a significant amount of protein (approximately 377 g of protein per day), equating to around 47% of the daily calories, with 46% coming from fat, and carbohydrate providing a mere 7% of calories.2 Likewise, Aboriginal diets in Australia have been extensively studied. The traditional Aboriginal diet is low in carbohydrate and promoted the maintenance of lean body weights and minimised insulin resistance. When Aboriginals transition to a modern western diet that is high in carbohydrate and refined fats, the incidence of metabolic disorders, obesity and diabetes rise markedly but interestingly even a temporary reversion to a traditional hunter-gatherer lifestyle causes ‘striking improvements’ in carbohydrate and lipid metabolism.3

a temporary reversion to a traditional hunter-gatherer lifestyle causes ‘striking improvements’ in carbohydrate and lipid metabolism

Hunter-gatherer populations will prioritise fatty tissue (such as bone marrow and organs) if able, to avoid spoilage and loss of nutrient-dense organ meat, and to provide the maximum amount of calories (and micronutrients) while avoiding the dire metabolic consequences of protein overconsumption.4 This is congruent with both the hunter and scavenger-dominant theories of human food acquisition, especially as both hunting and predator-confrontational scavenging are likely to have provided a large amount of the food for early humans.5 Fresh kills by both hominids themselves and other predators would have provided organ tissue and bone marrow—both high in fat (and fat-soluble vitamins), with the relatively lean tissue of wild game meats being a secondary fuel source to the fattier, and thereby more calorically and nutritionally dense tissue of organs and bone.

It should be noted, that there is considerable variation in the macronutrient content of hunter-gatherer diets. 229 hunter-gatherer diets from around the world were analysed using plant-to-animal subsistence ratios. A high variance in carbohydrate intake was found (approximately 3%-50% of daily calories). This variance is related to what is available based on climate and geography, and carbohydrate intake is inversely associated with latitude. In extremes of latitude (such as the Northern Tundra environments) higher proportions of animal-derived foods, and hence, protein and fat are consumed due to the relative abundance of large game-animals and scarcity of carbohydrate-containing foods. In comparison, higher carbohydrate foods such as fruits, tubers, and grains are more plentiful closer to the equator. However, the authors of this study noted that independent of the local environment the range of energy intake derived from carbohydrate in most hunter-gatherer populations is significantly lower than the minimum current dietary recommendations,6 and so, the recommended minimum amount of carbohydrate for modern humans is higher than the intakes of any of the hunter-gatherer populations studied. This begs the question: Have we in the last 50 years discovered a better diet than the one that we evolved to eat over many millennia?

Eat real food

Any rational approach to this topic could not conclude that we have suddenly ‘happened upon’ the best diet for the human being in the last hundred or so years. Animals (and remember that we are animals!) co-evolve with the environment around them and develop appropriately to match this. So rather than assuming that an incredibly high carbohydrate intake from ultra-refined and processed food is best for most people, most of the time, we should instead look at the evidence from our forebears (and from free-living humans in the wild now) and conclude that perhaps the best diet for most people, most of the time, is one that is between around 3% and 50% carbohydrate, with some functioning best on even higher amounts of carbohydrate, with the large variation accounted for by genetic (ethnic) predisposition and activity. In other words, eat an appropriate amount of carbohydrate for your ethnic (and therefore genetic) background and according to your energy requirements (i.e. the more you move, and the higher the intensity of that movement, the more carbohydrate you are likely to tolerate and benefit from). By taking an approach that recognises the ‘activity-dependent’ nature of carb requirements AND our genetic tolerance to carb intake (or as I have coined it a ‘Carb Appropriate Diet’ approach) we can avoid needless debate of which diet is better, high-carb or low-carb, and instead focus on what works best for individuals.

Much of this variation though can be achieved by simply eating a diet that is based almost exclusively on natural, unrefined foods (with room for some treats here and there!), and eating these foods ad libitum. When we based out day-to-day nutrition on natural, unrefined foods, the rest becomes mere window-dressing and I guess, that’s what both anthropology and nutrition science is demonstrating more and more…

eat a diet based almost exclusively on natural, unrefined foods and eat those foods ad libitum

References

1.            Mummert A, Esche E, Robinson J, Armelagos GJ. Stature and robusticity during the agricultural transition: evidence from the bioarchaeological record. Economics and human biology. 2011;9(3):284-301.

2.            Sinclair HM. The Diet of Canadian Indians and Eskimos. Proceedings of the Nutrition Society. 1953;12(01):69-82.

3.            O’Dea K. Westernisation, insulin resistance and diabetes in Australian aborigines. Med J Aust. 1991;155(4):258-64.

4.            Speth JD, Spielmann KA. Energy source, protein metabolism, and hunter-gatherer subsistence strategies. Journal of Anthropological Archaeology. 1983;2(1):1-31.

5.            Domínguez-Rodrigo M. Hunting and scavenging by early humans: the state of the debate. Journal of World Prehistory. 2002;16(1):1-54.

6.            Ströhle A, Hahn A. Diets of modern hunter-gatherers vary substantially in their carbohydrate content depending on ecoenvironments: results from an ethnographic analysis. Nutrition Research.31(6):429-35.

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