This lecture was initiated by a statement made at last year's AHS by the keynote speaker, Prof. Dan Liebermann, who said that “there were many Paleo diets”. A few prominent Paleo bloggers were quick to quote him and later that year the book Paleofantasy came out so I am glad to have the opportunity to try to subtentiate a completely different point of view here.
In Paleofantasy Prof. Marlin Zuk ask why pick up 2 million years and not 6 million or 30 million years ago? The answer lies in the major change in our digestive system in the transition to Homo 1.8 million years ago. Here is the composition of the Chimpanzee’s diet in terms of calories based on a paper by Conklin-Britain, Wrangham and others. When the fat from the by product of the fermentation of the high fiber content is taken into account we get a composition of 50 % fat, some 20 % protein and 30% sugar.
Much of the 50% fat is the product of fermentation by bacteria in a large colon which forms 52% of the Chimp’s gut. Our colon is only 21% of a gut that is 40% smaller than the Chimp's gut. With such small colon highly fibrous food is indigestible. And most plants in nature are highly fibrous. In the season there are some nuts that provide fat, fruits that provide little sugar and roots and tubers that are somewhat less fibrous than most plants and provide starch. So prof. Wrangham of Harvard, who studied primats and tubers and know they are too fibrous in a raw state, came up with the “Cooking Hypothesis” and identify starch from tubers as a major cooked source of calories for early humans .
So if we return to the most notable alternative hypothesis to one presented here, the Cooking Hypothesis, It is evident that starch metabolism and specifically tubers consumption in significant quantities is a post Paleolithic phenomena. In addition, evidence for habitual control of fire only shows up clearly from 400-200 Kya which is 1.2 million yearts after the appearance of early Homo erectus. Thirdly, as I will show in the next slides Isotope studies on pre-agricultural humans all confirm low plant consumption in the Paleolithic. it seems that the Cooking Hypothesis can quite convincingly be discarded
However, based on a study published in 2009 by Hancock et al genetic adaptation to tuber diet, such as high starch metabolism, high rate of folic acid biosynthesis and detoxification of tubers poisonous glycosides is prevalent only in farming groups that consume high tuber diet and not in hunter gatherers. So it transpires that although cooking is ubiquitous for hundred of thousands of years we were not genetically adapted to consume tubers until few thausands years ago.
To prove that only agriculture brought with it significant quantities of starch a genetic study of the bacteria S. mutans which feed on starch and is responsible for our carries found that they had a population explosion around 10,000 years ago.
Another genetic study by Perry et al shows that we are still not fully adapted to consume large quantities of starch of any kind tuber or otherwise. The AMY1 gene allows us to metabolize starch with lower insulin secretion which is good.You will notice that most people in the studied sample have less than theadapted population median, marked by a green line on the graph. Based on the previous evidence for explosion of starch feeding bacteria 10,000 years ago It is quite likely that the prevalence of multiple copies of AMY1 is as recent as agriculture. As can be seen on the left graph John Hawks found out that most of the genetic changes in the last 80 thaousands years took place around the time of the agriculture revolution.
Lets turn now to Archaeology. Almost every archaeological prehistoric site contains almost exclusively stones and bones. Animal bones with cut marks from stone tools. You can see a typical table reporting taxa and number of bones from a paper by Rabinovich et al.
Use marks studies on the stones all show that the main reason for their prolific productionwas to hunt and butcher animals. You have to be blind not to see that these are cultures of hunters. Yes, in very few sites one finds a single grinding stone but untill the period just prior to the agriculture revolution they are few and far between in comparison to the hundred of thousands of hunting and butchering stone tools.
Just prior to agriculture twenty to ten thousand years ago, Petals, Storage bins and large quantities of grinding stones show up, indicating that when significant quantities of plant material are consumed they do show very well in the archaeological record.
Recently plant residues were found in teeth plaque showing that plant food was consumed during the Paleolithic. However It is seasonal and costly to obtain and prepare for safe consumption so the quantities, in a nomadic culture could only be limited.
Recent groups of Hunter gatherers are a problematic model for Paleolithic humans as they live close to farming communities and most importantly, large animals, which formed most of the Paleolithic target prey animals have gone extinct or largely diminished prior to ten thousand years ago. Despite this, of 10 groups for which detailed studies were carried out, 5 groups consumed approximately 80% animal food and only 2 groups from very specific semi desert area consumed less than 50% animal sourced food.
However as can be seen from studies of Neolithic populations the method is very sensitive when humans do eat significant quantities of plant foods. In this Isotope study Pearson et al were able to distinguish between farmers’ social classes based on a slightly higher consumption of meat.
The premier geochemical tool for quantifying the relative amount of animal sourced food in the diet of ancient peopleis the content of Nitrogen isotope 15 in bone colagen and therefore only individual from about 50,000 years ago onward can be studied. Every single study carried on tens of pre-agricultural humans show them to be top carnivores. Their position above Hyaena and wolf is interpretaed as indicating a consumption of large animals. Recently there have been claims that humans metabolise nitrogen differently and therefore these studies tend to overestimate animal food consumption.
Another method of quantifiying animal sourced food in relation to plant sourced food is by measuring Strontium and Barium in relation to calcium in animals and human teeth. In a study that was published this year Balter et al state that “Early Homo is indistinguishable from carnivores”.
Another source of information is Paleontology. Researchers noticed the association of the appearance of the Homo species with the extinction of large carnivores. For example a study that was published this year in Plos one by Werdlin and Lewis found that in Africa that phenomena is evident at the time of the appearance of Homo erectus 1.7-1.5 Mya and another pair of researchers Palombo and Russi identified in an earlier paper that the same phenomena took place in Italy when Homo arrived there half a million years ago.
Another line of evidence come from comparative animal behavior. Comparing the behavior, especially concerning food acquisition, among humans, 11 carnivores and 14 primates Thompson found that in 6 behaviors out of the seven studied humans behave like carnivores. He therefore concluded that “there is incontrovertible evidence of the convergence of human behavior with carnivore behavior”
Wolf is another widely distributed species. his wide range of prey size, just like humans cause his widespread adaptability. I always think of wolf as a good example of an omnivore who can and does eat plant food but his diet is basically carnivorous. Researchers have suggested that the drive to domesticate the wolf was the help it could provide in hunting.
Life history is the timing of key events in an organism's lifetime and is a very important sub-field of evolution studies. It always pazzelded scientists why, despite longer childhood, weaning in human takes place half as early as in chimps.2-3 years as opposed to 4-5 years in chimpsIn a study published this year Psouni et al found that shorter weaning periods typify carnivores and therefore concluded that humans’ short weaning period in comparison to Chimpanzee is a proof for the emergence of carnivory as a process fundamentally determining human evolution. Short weaning periods are made possible in carnivores by the high nutritious value of meat. Humans are dependent on meat for short weaning and dependent on short weaning for high fertility.
This table here is essential to understanding the next life history evidence. It was compiled by Kuhn and Stiner and it shows that large game hunting is 6 to 10 times more efficient in terms of obtaining calories than gathering roots and tuber. Even hunting small game is two times more efficient than gathering tubers.
This graph from one of the most cited paper I know by Kaplan et al,to my mind, is the ultimate explanation of why humans could not rely on plant food as a major food source. Kaplan and his colleagues found out that it takes 20 years of investment in education for a hunter to stop being dependent on others for his food supply compared to 5 years for the chimp. So much knowledge is associated with hunting that a hunter reaches the pick of his productivity at 40 years old. For 20 years other hunters have to obtain and share many more calories than they themselves need which indeed they do as the graph shows. Taking into account the enormous difference in efficiency between big game hunting and tubers collection it just doesn’t make sense that gathering plants is likely to leave time to obtain foods for others. Indeed food sharing as we have seen in behavior comparison paper of Thompson is uniquely carnivorous and here we see that it is the cornerstone of the pre-agriculture human society.
To sum up – for nearly 2 million years we were fully fledged carnivores. Our social organization, our behavior, our material culture our biology all co-operated in helping us being a fully fledged eurytopiccarnivore. So yes, my conclusion is that we had one Paleo diet – a Carnivorous diet with a very high percentage of animal meat and fat.How is this conclusion relevant to the present day Paleo practitioner? I think of Paleo not as a romantic reconstruction of the past but as a safety template. From that point of view plenty of meat and fat in the diet seems to be a good bet. Yes we did adapt to consume agriculture based foods but we have to take into account that the adaptation seems to be partial and most of us don’t know to what to extent we are genetically adapted to non-meat foods.
Carnivourus paleolithic diet miki ben-dor ahs13
Department of Archaeology
Tel Aviv University, Israel
Conklin-Brittain NL, Wrangham R, Smith CC
(2002) A two-stage model of increased dietary
quality in early hominid evolution: The role of
fiber. In: Ungar PS, Teaford MF, editors. Human
diet: Its origin and evolution: Greenwood
% weight (Conklin-Britten 2002)
% calories (Assuming 1.5 cal. fat/1 gr fiber)
Full explanation and references at http://www.paleostyle.com/?p=2001
Colon is 21% of a
smaller gut, ¼ of
Chimp colon, Little
B12, max. 8% of
Colon is 52% of the
Source of fat and B12
Milton, K. (1999).
wild primate foods:
do the diets of our
Wrangham proposed that cooking by Homo erectus 1.8 million years
ago allowed humans to consume tubers despite their significant
fiber content and humans smaller colon and teeth.
◦ Archaeological evidence shows habitual control of fire only begin
1.4 million years later
◦ Genes that promote significant starch metabolism appear at the
earliest only 1.6 million years later.
◦ Genes to cope with tubers’ low folic acid content and
detoxification of tuber glycosides appear only recently and only
among agricultural populations that consume domesticated
◦ Nitrogen Isotope studies confirm low plant consumption in the
late Paleolithic even though cooking was well established.
◦ Meat and fat consumption offer more parsimonious solution to the
fiber problem as they are energy dense and do not have fiber so
do not require cooking to be metabolized.
Genetic adaptation only in groups with post-
Paleolithic consumption of tubers to:
•Starch and sucrose metabolism
•Folic acid biosynthesis
•Detoxification of plant glycosides
All isotopic studies confirm that Upper Paleolithic humans
were top carnivores
Strontium and Barium analysis in human and animal
teeth from approx. 2 MYA show: “Early Homo (is)
indistinguishable from carnivores” (Nature 2012)
Africa 1.5 MYA - “The appearance of Homo is marked by a sharp drop in
the number of large carnivores (>20 kgs) but not small carnivores”
Italy 0.5 MYA – Homo appear. Large carnivores drop despite increase in
Werdelin L, Lewis ME (2013) Temporal Change in Functional Richness and Evenness in the Eastern African
Plio-Pleistocene Carnivoran Guild. PLoS ONE 8(3): e57944.
Large Carnivores Small Carnivores
Signs of competition between early humans and large carnivores
“there is incontrovertible evidence
of the convergence of human
behavior with carnivore behavior”
2nd Widest geographic
Prey size: 1000 kgs – 1
Preying on young and old
Prey size: 6000 kgs - 1 kg
Preying on adults
“our findings highlight the emergence of
carnivory as a process fundamentally
determining human evolution.”
Weaning in humans 2-3 yearWeaning in Chimps 4-5 years
Kuhn, S. L., & Stiner, M. C.
(2006). What’s a Mother to
Do? The Division of Labor
among Neandertals and
Modern Humans in
Anthropology, 47(6), 953-981