In 1988, physicians S. Boyd Eaton and Melvin Konner, and Emory University anthropologist Marjorie Shostak published “Stone Agersin the Fast Lane: ChronicDegenerative Diseases in Evolutionary Perspective” in the American Journal of Medicine. They expanded this paper to produce the book, The Paleolithic Prescription.
By the way, Shostak lived among African hunter-gatherers for two years, and wrote the book Nisa: The Life and Words of a !Kung Woman.
In these works, Eaton et al provided their estimates of the fat contents and composition of stone age diets. They based their estimates on known nutritional values of 43 different wild game animals and over one hundred species of plants consumed by modern day hunter gatherers.
The data on nutritional value of wild game came largely from Ledger, who dissected 220 different animals of 16 species.  Ledger worked in the field of zoology, and published this data in a zoological journal, for the purpose of comparative studies of African mammals, so we have no reason to suspect that he had any interest in advancing any nutritional dogma.
We have a very important reason to focus on the nutritional value of African mammals. The human genome evolved to the present species, H. sapiens sapiens, in Africa, as an adaptation to the African environment, over the course of 6 million years (from the divergence from the common ancestor of great apes and humans). Of 6 million total years of hominin evolution, the 50K years that have passed since humans left Africa constitutes only eight-tenths of one percent. Virtually all of human evolution took place in Africa, so we can expect our baseline physiology to be more adapted to the diet available to our African ancestors, than to any human diet that emerged after the African exodus in northern environments.
The animals included goat, Cape buffalo, warthog, horse, wild boar, antelope, beaver, muskrate, caribou, moose, kangaroo, turtle, opossum, wildebeest, Thomson’s gazelle, kob (waterbuck), pheasant, rabbit, impala, topi, deer, and bison. The fat content of meat from these animals ranged from a low of 1.2 g% in kangaroo, to a high of 5.4 g% in wildebeest.
In 1964, Ledger and Smith reported the results of their dissection of 40 Uganda kob, 10 mature and 10 immature of either sex. They found that “all kob had a low level of carcass fatness (maximum 6.2 percent), associated with high carcass yields” and when compared to steers, the “ratio of fat to lean showed a higher proportion of lean in kob carcasses. The food value of kob per pound liveweight is superior in terms of animal protein and inferior in terms of calorific value to that of steers.” Indeed, a modern grain-fed steer has around 25% of the carcass as fat, making it 4 times fatter than the kob.
Eaton et al assumed a diet providing 35% of weight from animals, and 65% from plant, and a total food consumption of 2250 g (nearly 5 pounds) daily to provide around 3000 kcal daily. I consider this a very reasonable amount of food. I have measured my own food intake many times and when eating 65% plants and 35% meat, it consistently has ranged between 4 and 5 pounds. The following provides an example day on which I ate 4.7 pounds of food, which I published in The Garden of Eating:
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Ledger’s analysis of wild game meat showed that on average a 100 g portion provides 133 kcal, 22 g protein, and 4.3 g fat, 32% of which, on average (based on 17 species evaluated), occurred as polyunsaturated fats (ranging from 20-60%, largely as linoleic acid, omega-6), and well under 40% saturated fats. For comparison, four types of untrimmed domestic meats (beef, pork, lamb, ham) can supply an average of as much as 386 kcal and 29 g fat per 100 g, and average 45% saturated fat, and only 7 percent as polyunsaturates.
To estimate the contribution of wild plants to fat intake, they used an analysis of 36 wild foods eaten by the Hadza, the San (Bushmen), and other African tribal groups, which indicated generally a very low fat content, of which 39 percent, on average, occurred as polyunsaturated fat.
Isolated fats in Paleolithic diets
Hunter-gatherers do not have any fluid seed, nut, or fruit (olive, avocado) oils. I don’t think we can consider olive oil, avocado oil, or coconut oil paleo foods, since production of these fats requires technology not available in the stone age.
Like modern !Kung, Paleolithic hunter-gatherers living fifty thousand years ago also did not have pots necessary for rendering, i.e. refining and isolating, animal fat. Nor did they have cream or butter. Based on this, I have come to realize that I can’t consider isolated lard or tallow or similar refined, animal-derived fats “Paleolithic” foods. We really can’t consider any isolated oil, whether animal or vegetable, a paleo food.
Actually, after thinking about this for some time, I have come to realize that all isolated fats belong to the class of refined foods; fragments of the whole from which they came. I have also realized that adding these to the diet constitutes a significant deviation from ancestral nutrition. Using the paleo paradigm, because these foods deviate significantly from anything had by humans 100 thousand years ago, we have to consider them suspect from the get go, guilty until proven innocent.
Effects of Paleolithic cooking techniques on dietary fat
If you have television and want to see how hunter-gatherers cooked meat, watch the Bizarre Foods episode titled “Adventures in the Khalahari,” in which Andrew Zimmern visits the Ju (!Kung, San) people. They either throw the meat directly into the fire, or bury it in the ashes. Similarly, as reported in the following passage, Australian Aborigines cooked meat by burying it in a pit.
“A large fire was made in a depression in the sand, and stones and shells were heated. Small green branches were placed on top of the stones and the wallaby was flung on these. After 5-10 minutes it was taken off the fire, placed on a layer of green leaves, and the singed fur was removed with a tomahawk. The first cut was made horizontally on the ventral surface at the level of the anus, and the next on the dorsal surface along both sides to sever the leg muscles. Another cut was then made from the anus to the neck. The viscera were pulled out; and the kidneys, liver, heart and lungs, and the omental and mesenteric fat were separated from the rest, and cooked [directly] on the hot stones and coals for 5 minutes [Editorial note: allowing the fat to seep into the fire]. The cooked lungs were used to soak up the blood inside the carcass and then eaten. The offal was regarded as a delicacy by everybody and a certain amount of squabbling always followed its distribution. The tail was cut off, and during the cooking was put on or alongside the body. The carcass was laid flat, dorsal side downwards, on the hot stones and ashes and the body cavity was filled with hot stones. Sheets of paperbark formed a cover over the animal, and sand was scooped out to make an oven. Wallabies weighing 15-20 pounds were cooked for 25-35 minutes. Everything edible was eaten except the stomach and intestines. The skull was cracked open to get the brain, and the bones were broken to extract the marrow.” [Source: Anthropology and Nutrition, vol. 2 of Records of the American-Australian Scientific Expedition to Arnheim Land, ed. C.P. Mountford (Melbourne: Melbourne University Press, 1960).]
In any of these methods, hunter-gatherers lost significant amounts of animal fat into the fire, stones, coals, ashes, or soil. Indeed, since paleo people didn’t have neolithic pots we really can’t consider cooking in such pots a Paleolithic technique, and I believe it important to notice that cooking meat in neolithic pots results in capturing more of the fat of foods than a hunter-gatherer could capture. We especially can’t consider frying in fat a Paleolithic diet method.
Regarding pemmican, consider that one hundred thousand years ago, no human had the technology required to render fat to produce pemmican, even if we assume available African game could have provided the required amounts of fat (it didn't). The invention of suitable pots occurred about the time of the agricultural revolution. This means that the human genome has probably not adapted to the level of dietary fat that is possible through the use of this technology any more than it has adapted to the use of cereal grains.
In addition, consider that, prior to the 20th century, people used animal fats for many purposes other than eating. Before the petrochemical age, animal fats were used as lubricants (e.g. grease for axles), for tanning leather, and to make soap, salves, paints, wood finishes, and candles. Even Inuit used seal oil and blubber to fuel fires and candles. These uses took animal fats out of the food supply, reducing the potential fat content of the diet. When petrochemicals or vegetable oils replaced animal fats for these purposes, this increased the animal fats available for food use.
Discussing cooking techniques appropriate for a Paleolithic approach, Eaton et al comment:
“Roasting, baking, and steaming (water is poured over hot stones as at a Polynesian luau) are techniques used by recent hunters and gatherers and are probably ancient. While all cooking procedures affect the nutrient content of food, these traditional techniques are relatively healthful. Baking and roasting reduce the fat content of meat [note: so long as you don’t retain fat of juices] while steaming (in contrast to boiling) minimizes vitamin loss. Furthermore, none of these methods add fat. Recently studied hunters and gatherers do not fry their food, chiefly because they lack appropriate cooking vessels….
“Nonstick pans should be used to cut down on fat or oil. Or, oil can be spread lightly with a paper towel. Vegetable oil sprays now available achieve the same result mechanically….
“With poultry, remove skin and visible fat. Defat gravies with a bulb syringe or skimmer.”
So, how much fat did Eaton et al estimate to occur in a Paleolithic diet?
If you take 35% of the 2250 g diet as meat, supplying 4.3 g fat per 100g, you get ~34 total grams of fat. Eaton et al estimated an additional ~40 g of fat supplied by plant foods 3 percent fat on average), resulting in a total fat intake of about 70 g daily, or about 21 percent of the total 3000 calories consumed. This would translate to only 42 g of fat for 2000 kcal, and only 32 g fat for 1500 kcal.
If you take 65% of the 2250 g diet as meat, supplying 4.3 g% fat, you get 63 g fat daily from animal food, and an additional 24 g from plant food, for a total of 87g fat. That works out to just 26 percent of calories from fat, a minor difference from the opposite plant-animal ratio, still very low in fat.
Because wild game and plants had a relatively high percentage of polyunsaturated fats (~30%) and lower percentage of saturated fats, Eaton et al also estimated a high P:S ratio in Paleolithic diet compared to modern diets, and suggested that this accounted for the uniformly low total cholesterol levels found among hunter-gatherers, ranging from 106 (Pygmies) to 141 (Canadian Eskimos).
Eaton et al concluded:
“Late paleolithic humans must have obtained, on average, between 20 and 25 percent of their calories from fat. Of this, polyunsaturates exceeded saturates; a typical P:S ratio might have been 7:5 (which can also be expressed as P:S = 1.4:1).”
So, it appears that Eaton et al did not have evidence or belief that evolutionary diets had high fat (or low carbohydrate) contents. Indeed, they stated:
“Between 1910 and 1976, the consumption of fats in the United States increased by about 25 percent so that, currently , fat makes up about 42 percent of the calories consumed by average Americans. Of this fat, more that twice as much is saturated as polyunsaturated. This level of fat consumption is unprecedented in human evolutionary experience, and results in diseases that kill us, but that are uncommon in countries where fat represents a much smaller proportion of the diet. In rural Japan, for example, only 10 to 12 percent of daily calories come from fat (with a P:S ratio of approximately 1:1) and the prevalence of coronary heart disease among the Japanese is only a small fraction of ours.”
Taking these and other data on the health effects of dietary fat into account, Eaton et al recommended that a modern rendition of Paleolithic diet supply only about 20% of calories as fat, with about 25% of calories as protein and 55% of calories as carbohydrate. They outline an implementation that provides 19% of calories as fat, 26% as protein, and 55% as carbohydrate.
So it appears that the notion that modern rendition of paleo diet should have a high fat and low carbohydrate content did not come from Eaton, Konner, and Shostak.
Next in this series, we will see what Michael Crawford and David Marsh, authors of Nutrition and Evolution, had to say about fat in human evolutionary diets.
1. Ledger, HP. “Body composition as a basis for a Comparative Study of Some East African Mammals.” Symposium of the Zoological Society of London 21 (1968): 289-310.
2. Ledger HP, Smith NS. The carcass and body composition of the Uganda Kob. Journal of Wildlife Management 28(4), October 1964