In May, 2013, I posted a response to the January, 2013 TED lecture by Christina Warinner in Norman, Oklahoma, titled “Debunking the Paleo Diet”.
The website where my response was first posted is no longer in existence, consequently, because this lecture is often referenced, and has now had well over a million views, we feel it is worth re-posting my rebuttal here at thepaleodiet.com.
Christina Warinner’s “Debunking the Paleo Diet”, obscurantism at its very best.
by Mark J. Smith, Ph.D. – May 12, 2013
(TED lecture link: https://www.youtube.com/watch?v=BMOjVYgYaG8)
After receiving a number of requests to comment on the TEDxOU lecture by Christina Warinner, I sat down at my laptop to begin a rebuttal and was wondering what kind of a title this work warranted. With fantastic appropriateness, the screen saver application scrolled the word “obscurantism” across the screen. Obscurantism, from the Latin obscurans, “darkening,” is the practice of deliberately preventing the facts or the full details of some matter from becoming known. Now some may suggest that I am out of line in suggesting that Dr. Warinner is deliberately holding back pertinent information; but, I simply have a difficult time believing that someone who obtained a Ph.D. from Harvard is not able to do a modicum of research within the scientific community about the actual topic she is proposing to “debunk” – the Paleo diet. Dr. Warinner introduces herself as “an archeological scientist who studies the health and dietary histories of ancient (note that she does not put a timeline on “ancient”) peoples using bone biochemistry and ancient DNA.” This certainly sounds impressive; however, from her comments throughout the lecture, it is obvious that her knowledge of the Paleo diet; or perhaps more appropriately, lack of knowledge, has been obtained from non-scientific sources and is simply inaccurate on a number of important issues. I will address these inaccuracies when I go through the time-line of her lecture; but, for Dr. Warinner to represent the Paleo diet as a fad diet (and it is spelt fad, not phad as is done in the lecture introduction) with no scientific backing, is tantamount to academic fraud or; at best, academic negligence. At a minimum, anyone can go on-line and do a quick search in the US National Library of Medicine’s “PubMed” to realize that there is a significant body of peer-reviewed research promoting the health benefits of adopting a Paleolithic diet. With the recent media attention of the research (//www.nejm.org/doi/full/10.1056/NEJMoa1200303) touting the health benefits of the Mediterranean diet, a diet that I suspect Dr. Warinner would endorse, it might have been useful, as just one example, for Dr. Warinner to be aware of the work of Dr. Lindeberg from the Department of Medicine at The University of Lund in Sweden. Among many other benefits, Dr. Lindeberg’s research team has shown the Paleolithic diet to be more effective than the Mediterranean diet at improving glucose tolerance in individuals with ischemic heart disease (//www.ncbi.nlm.nih.gov/pubmed/17583796). But no; unfortunately, the audience does not get the benefit of such knowledge because Dr. Warinner is either ignorant of it or is choosing to not share such research. So unless the Paleo movement has become so powerful that sales of certain non-Paleo foods are declining and certain lobbying groups need some propaganda out in the main stream, I suspect it is the former. But either way, it is an extremely weak position from which to try and “debunk” a well-researched field of nutritional science.
At the time of writing this rebuttal, Dr. Warinner’s lecture has been available for three months and has had over 150,000 views. My biggest concern is that of those viewers choosing to share their opinion, over 82 percent actually see this presentation favorably. Now, aside from individuals that would choose not to eat a Paleo diet, regardless of what the scientific literature and clinical data demonstrates – for example, someone who chooses to not eat meat based on their own personal belief system (which I completely respect) – many people viewing this lecture might choose not to adopt or even stop following the Paleo diet thinking it is now the wrong way to go. Because to those that are unaware of the scientific research or the clinical benefits supporting the Paleo diet, Dr. Warinner’s presentation may have seemed logical and well-researched, when it was not. And in a case such as this, Dr. Warinner is doing a disservice to people who could obtain the same clinical benefits that Dr. Lindeberg demonstrated in his clinical study, and that I, and countless others, have shown with their clients.
I have been involved with the Paleo diet for the better part of 25 years (usually considered a little longer than a fad time-frame) and have researched, written, and presented about the Paleo diet and; perhaps even more importantly, worked clinically with individuals who have benefitted from adopting this way of eating. Professor Loren Cordain of Colorado State University has been (and still is) one of the main forces in researching the Paleolithic diet. Dr. Cordain was actually my advisor for my Masters degree and after obtaining my doctorate in Physiology with a research specialty in cardiovascular disease, there was an obvious interest for me in nutrition and disease prevention. Consequently, during my early post doctoral years, I was privileged to be involved with Dr. Cordain’s research from the very early days and I did a significant amount of work with autoimmune patients; I was even at the lunch table when he first played host to Dr. Boyd Eaton who wrote the pioneering 1985 article on Paleolithic nutrition published in The New England Journal of Medicine. One of the important memories that stands out for me in those early days, is that anything, and I want to emphasize anything, Dr. Cordain wrote about the Paleo diet was backed up by a peer-reviewed journal article. Nothing has changed today. So for Dr. Warinner to have an image of one of Dr. Cordain’s books on her slide show presentation and suggest that there is no scientific support is either disrespectful or blissfully ignorant. If you want to read a significant proportion of the science supporting the Paleo diet, you can go to Dr. Cordain’s website //thepaleodiet.com and review any one of the 61 scientific papers about Paleolithic nutrition Dr. Cordain has published in peer-reviewed journals. By way of a comparison, Dr. Warinner lists a total of 7 peer-reviewed publications, none of which are actually about Paleolithic nutrition. One paper, which Dr. Warinner discusses in her lecture, may be considered pertaining to the Paleolithic-Mesolithic boundary; but, she clearly does not have a published record on Paleolithic nutrition.
So let us examine her presentation in a little more detail. Well, to start with her choice of wording for her lecture and her demeanor at the outset reeked of arrogance and sarcasm, adjectives not typically recommended for scientific presentations. But when lecturing to a non-expert audience, it probably sounds appropriately humorous; however, when one realizes that half of what she is saying is simply inaccurate, the humor quickly dissipates. The first inaccurate statement she makes is that the diet is targeted to men. I have absolutely no idea how she came up with this because, as she does throughout her lecture, no mention of the source is given. However, if she actually read the scientific literature on the topic, she would realize the foolishness of this statement. Or, since she appears to not enjoy reading scientific papers on this topic, it might well have been useful to have at least skimmed the chapter titles of Dr. Cordain’s latest book, and in my opinion his best work to date, The Paleo Answer. She would then have realized that Dr. Cordain has a whole chapter dedicated to the special considerations for women following the Paleo diet. It would have also be useful for her to know that Dr. Cordain referenced over 900 sources in writing this latest book, with only a handful not coming from peer-reviewed journal articles. Robb Wolf, author of the Paleo Solution, and also a former student of Dr. Cordain, has also written a rebuttal to this lecture and I highly recommend reading it (see the link at the end of this article). So with regard to Dr. Warinner’s assertion that the Paleo diet is targeted towards men, Robb Wolf, who also found this surprising, searched Google for “Paleo Diet” and then selected images. You can go to Rob’s rebuttal to see what comes up, simply try it yourself or take my word for it that just as many women, if not more, come up in the typical pre-post pictures. So unless Dr. Warinner has some special gender biased Google search engine, it appears she deliberately chose this depiction to suit her story line and presentation style.
Dr. Warinner then states that the Paleolithic diet can be broken down into four parts:
- Our agricultural diets today make us chronically ill and are out of synch with our biology.
- We need to abandon these diets, move back in time to the Paleolithic and eat more like our ancestors from over 10,000 years ago.
- We know what these diets were like and they were mainly meat based supplemented with vegetables and fruits, and some nuts and oils, but definitely did not contain grains, legumes or dairy.
- If we emulate this ancient diet, it will improve our health and make us live longer.
Finally, I’m almost in agreement with a position of Dr. Warinner, almost. However, the depiction of “mainly meat” based, is a classic anti-Paleo position that is simply incorrect. If you are truly well read on Paleolithic nutrition, you will know that the Paleo diet is higher in protein than the typical American diet because the animal protein advocated is lean or perhaps better stated, natural. And “meat”, by definition, is animal flesh and so includes all animal protein, it’s not just “red meat”. However, none of the leaders in the Paleo movement advocate “supplementing” the diet with vegetables and fruits; rather, it is promoted to eat plenty of these foods as well as a wide variety. Of course at certain times of the year during Paleolithic times, and in particular climates, meat consumption would have increased as vegetation became less available, something that Dr. Warinner actually pointed out herself later in her lecture like it was a new revelation! So other than that point, she is correct on what those of us in the Paleo movement believe. And I find it particularly ironic that she actually spends a significant portion of her lecture supporting these positions without, apparently, realizing it.
However, at 2:40 in the lecture, Dr. Warinner makes a bold affirmation that this Paleolithic template, “as promoted in popular books, on TV, on self-help websites and in the overwhelming majority of popular news articles (notice that no reference is made to the many peer-reviewed publications) has no basis in archeological reality.” Her corresponding slide adds the term “virtually” and swaps “reality” for “record” which actually makes her position even more tenuous. That is because there simply is a clear record in the peer-reviewed literature and it is quite unbelievable that it is basically being ignored in this lecture. As an archeologist, one would expect Dr. Warinner to be aware of the work of Dr. Michael Richards (//anth.ubc.ca/faculty/michael-richards/). Dr. Richards is one of the world’s leading archeological scientists and has published well over a hundred peer-reviewed articles, three of which have been published in the esteemed journal, Nature. Most researchers would call it a successful career to get just one article in Nature; rest assured, an individual publishing three times in Nature is held in high regard in the scientific community. Dr. Richards’ body of work, as well as many other researchers, lays out the very record that Dr. Warinner claims does not exist. (Update: As of June 2016, Dr. Richards’ publications are now over 300 with five publications in Nature and two in Science – https://scholar.google.ca/citations?user=0fMpFU8AAAAJ. Dr. Warinner has also published eleven additional studies since the writing of this rebuttal – //www.ncbi.nlm.nih.gov/pubmed/?term=Warinner%20C[Author]&cauthor=true&cauthor_uid=27254246 (the paper with the author CB Warriner is not Christina Warinner) – however, none provide support for any arguments made in her TED lecture).
So on to the “myth busting” which Dr. Warinner begins with the “meat myth”. The start of this section makes a huge deal out of the fact that humans, unlike carnivores, cannot make vitamin C and are dependent on vitamin C from plants. Okay; but since humans are omnivores and not carnivores, this point is completely irrelevant, as are her comments about humans having molars and a longer digestive tract than carnivores. Let’s just be clear here, humans are omnivores, that’s meat and plant consumption. Dr. Warinner then brings up the genetic adaptation to milk consumption and I wonder if she is aware of how the selective pressure to this adaptation in northern Europeans came about? Dr. Cordain was way ahead of the pack on this issue and has written a fascinating piece on the mechanisms by which lactase persistence came about. Essentially the adaptation to milk consumption in adulthood came about as a result of the negative consequences of wheat consumption and was simply the lesser of two evils. Just because some of the world’s population can tolerate milk does not make it the wonder tonic that the dairy industry obviously purports it to be. The negative consequences of milk consumption are well documented in the scientific literature and Dr. Cordain’s latest book details all of it in Chapter 5. Or you could just use common sense and ask yourself if you think it a good idea to consume filtered blood that was intended for a growing calf? A slide of some corn fattened meat is then shown and we are told that this kind of meat is nothing like the meat Paleolithic humans would have eaten; they would have eaten much leaner meat and also eaten the marrow and organs of the animal. Seriously? Again, she obviously has not read any of the literature on this for her to make such a statement. Obviously the animals would have been leaner because they weren’t crammed into a pen and fed . . . oh yes, grains! Paleo diet promoters are well aware of this and advocate the same. I actually found it hard to continue watching at this point because one is now realizing for a certainty that she has done no credible research on Paleolithic nutrition and you question why you are giving her the time of day. The point was also made that the animals eaten would probably have been small. Granted, small animals would have been included within the diet; but, the research shows a variety of hunted animals ranging in size. And, I do not think one could consider bison to be small.
At 4:56 a rather important statement was made . . . “Now sure, people did eat meat and especially in the Arctic and areas where there’s long periods where plants are not available, they would have eaten a lot of meat. But people that lived in more temperate regions or tropical regions would have had a very large plant portion of their diet.” So, again, there is nothing new here; but, Dr. Warinner appears to use this statement as a means to educate Paleo advocates, but this has long-been recognized by the Paleo diet researchers. In fact, in 2000, Cordain et al. published a paper in The American Journal of Clinical Nutrition (Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets – //ajcn.nutrition.org/content/71/3/682.full) that showed the ratio of plant to animal foods in the diet ranged from 35/65 to the exact opposite, 65/35. However, out of the 229 hunter-gatherer societies studied, 73 percent obtained more than 50 percent of their subsistence from animal foods, whereas only 14 percent obtained more than 50 percent of their subsistence from plant foods.
At 5:11, Dr. Warinner begins a detailed section “So where does this meat myth come from?” and continues to discuss the pitfalls of nitrogen stable isotope analysis as a means of determining the composition of Paleolithic diets. I think this is a particularly important section because I’m pretty sure that most people would simply take her final conclusion at her word, because, one, she is an archeological scientist with a Ph.D. from Harvard, and two, most listeners are not going to know if what she is stating is accurate or not. I am not an archeological scientist but I have read many of the cited papers that use nitrogen stable isotope analysis as a basis for determining ancient diets and I know that papers using this technique are still being published in the top peer-reviewed journals, including Nature. Consequently, my first thought was that researchers in this field would likely be well aware of any potential errors and account for them when interpreting the data. So I thought it might be useful to reach out to Dr. Michael Richards, as previously mentioned, one of the world’s leading archeological scientists, to get his input on this section. As well as being a Professor at The University of British Columbia, Dr. Richards is a Professor in the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. So it was not particularly unusual that when I reached out to Dr. Richards, he was in the middle of travelling to and from Europe with little access to quality internet for viewing video. So I provided Dr. Richards the exact transcript of Dr. Warinner’s lecture from 5:11 to 8:25 and have included it at the end of this article for anyone that wants to read the content. Rather than interpret Dr. Richard’s comments, I think it best that his e-mail communication simply be shared, which is as follows:
“Just a quick comment from the airport, but I think what she is stating is pretty disingenuous. Yes, there are issues with variability in nitrogen isotopes between ecosystems, but we know this, and work to establish the nitrogen isotope baseline for each region. The recent bone isotope studies in Palaeolithic Europe include measurements of animals from the same time period and ecosystem as the humans, so her criticisms don’t make sense in this context. Indeed she acknowledges this in her last sentence, so now we do have a good idea about Palaeolithic ecosystems and nitrogen variability, and in each case Neanderthals and early modern humans in Europe plot as carnivores, indicating that their primary source of protein was likely herbivore meat.
One thing though that she does not seem to understand is that isotope analysis tracks the source of dietary protein. Meat is significantly higher in protein than most wild plants (certainly the plants available in Palaeolithic Europe) so if Neanderthals and modern humans consumed a lot of plants and some meat, then the main protein source would still be the meat, as the plants have such low protein contents. So, in my opinion the isotope and archaeological evidence taken together overwhelmingly supports the idea that the main source of protein in Palaeolithic human diets was animal protein (meat) but of course there were consuming plants, but not as their protein sources and not in significant enough quantities to register in their bone isotope values”.
So there you go then. Not the myth that Dr. Warinner would have the listener believe.
8:27 – On to Myth 2: Paleolithic peoples did not eat whole grains or legumes. Dr. Warinner spends considerable time and detail discussing the research that provides evidence that humans did consume these foods prior to the advent of agriculture, 10,000 years ago. Again, Paleolithic diet researchers are well aware of this; in fact, I think most would even give her more than the 20,000 years for which she is showing evidence of these foods being consumed and still say, so what? That’s because what Dr. Warinner fails to discuss is that the time length of grain and legume (and of course, dairy, despite not being discussed in this section) consumption is still a tiny fraction of time in human evolution, whether it began 10,000, 30,000 or even 100,000 years ago.
9:41 – Myth 3: Paleolithic foods are what our Paleolithic ancestors ate. Here Dr. Warinner talks about how all of our foods today are products of farming and are nothing like the foods that our Paleolithic ancestors ate. For the most part this is a correct statement; but, there is nothing in this section that has not previously been discussed by Paleolithic diet researchers, and the content does not do anything to “debunk” the Paleo diet. Just one example of this can be seen at Dr. Cordain’s website discussing the sugar content of fruit (//thepaleodiet.com/fruits-and-sugars/) where he states in the very first paragraph, “However, the common fruits we eat today bear little resemblance to their wild ancestors. Domesticated fruits are almost always larger, sweeter, and contain less fiber than their wild counterparts. Compare a Golden Delicious apple to a crab apple and you begin to get the picture.” So what has been done by Paleolithic diet researchers is to best mimic the Paleolithic diet using what is readily available to today’s consumer and the clinical data – again, something that Dr. Warinner appears to know little about – confirms the health benefits of such a prescription. And for what it’s worth, while at least most of us in the Paleo movement would argue for eating local, organic foods, I’ll still take New England blueberries, Mexican Avocados, and Chinese eggs over the typical grain-based breakfasts that most Americans eat, as do my clients that once suffered from chronic disease. Notice that Dr. Warinner does not actually discuss with us the nutritional quality of her example breakfast.
At 14:05, Dr. Warinner decides to “talk about some real Paleo diets.” After ground-breaking news that there would have been no one Paleo diet, that people would have eaten local foods, which would have been both, regionally and seasonally variable (see any number of peer-reviewed papers on Paleo nutrition to see that this is not new), she then takes us back 7,000 years to Oaxaca, Mexico to provide us the dinner menu. She tells us that dinner would be a far cry from anything you would find on a Paleo diet, despite five out of the six foods she named being Paleo; but, I guess her point was that legumes were consumed. This should not be surprising though since she did not actually provide an example diet from Paleolithic times; instead, and bizarrely, she was referring to the Holocene (well past the Paleolithic, which generally ended at the end of the Pleistocene about 12,000 years ago) when one would expect to see the introduction of non-Paleo domesticated plants.
The remainder of the lecture continues with a plethora of correct but obvious “Paleo diet 101” statements that are delivered with a tone of correction to Paleo diet advocates. This might be the most annoying trait of her lecture because it comes across as if she is the first to provide this information to the public, when, as I have already stated, she is simply repeating what Paleo diet researchers have already determined and used to form the basis of the Paleo diet itself. Unfortunately, she does not realize this because of her obvious lack of knowledge about the Paleo diet that she demonstrates throughout her lecture. Here’s a perfect example: at 15:40, Dr. Warinner, referring to diets from Paleolithic times, states, “There are some general observations we can make. One is that they are regionally variable, people who live in the Arctic have and always will eat something different than people that live in the tropics. They have different resources, so people who live in places where there are no plants tend to eat more animals and people who live in places where there are plants tend to eat more plants and they would be seasonally variable.” Aside from making an incredibly obvious statement, the details of this have already been ascertained by Paleolithic researchers, a point I made earlier when referencing Cordain’s paper “Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets.”
At 16:58, referring to how primitive people ate, Dr. Warinner states “But it’s almost impossible for us, now, to eat this sort of diet, 3 billion people cannot eat like foragers on this planet. We are simply too big.” Now I have used the Paleo nutritional template for nearly 25 years and not once did I need to resort to foraging. The point Dr. Warinner fails to realize is that those of us that follow the Paleo diet are simply following a template that best mimics what our ancestors ate using the foods available to us today. No Paleolithic advocate has ever said we are eating exactly as our ancient ancestors did and most individuals are not following it to the letter either. My clinical experience, as well as many others, has been that an 80-percent compliance, for most healthy individuals, keeps one’s body composition where it should be and wards off chronic disease. However, and not surprisingly, individuals that have chronic disease get better results the closer they stick to the template of clean animal protein, vegetables, fruits and some nuts and seeds. In fact, there have been many incredible success stories from individuals suffering from an autoimmune disease that have followed a very strict compliance to the diet. Certainly, one of the elements holding back some individuals from eating this way can be the cost. Vegetables and fruits are certainly more expensive than grains and legumes, and free-range animal protein costs a lot more than mass-produced, low-protein processed meats. But from a global economic perspective, a ton of money could be saved in our medical system if we could get more people to eat this way. It was interesting watching the HBO special “The weight of the nation” and hear vegetable and fruit growers arguing that their products could be just as inexpensive as grains if they were to receive the same subsidies as the farmers growing grains. It certainly is puzzling that we subsidize the production of foods that have been shown to have negative consequences on our health and not the vegetables and fruits that everyone would agree are healthy for us.
Another way to look at the Paleo diet is to simply think about eating what nature provides us to eat. I often ask people to imagine being thrown out into the wild and you will quickly realize that your template for immediate sustenance will be the very foods prescribed on the Paleo diet template. The study on the 229 hunter-gatherer societies by Cordain et al., demonstrates this well. Further, any argument over the archeological record of what Paleolithic humans ate is unimportant to the individual that adopts the Paleo diet and obtains great clinical results. In fact, I have done a number of lectures to church congregations where the belief system is completely non-congruent with the archeological record and so obviously I do not spend much time discussing the same as to why humans should eat this way. However, there is no need to do so because I can simply discuss the clinical data and the current studies that support the argument that we do better when adopting a diet that limits grain, dairy and legume consumption.
While a great visual, I had to wonder what Dr. Warinner thought the sugar cane demonstration did to debunk the Paleo diet. This latter section of the lecture would really be better supported by a title such as “Our modern day processed foods make us sick” rather than the chosen title. And perhaps all individuals that care about what they eat, whether they be Paleo advocates or vegans, can all agree that highly processed foods are bad for us and do what we can to improve this aspect of our food supply. For example, I have not met any Paleo advocates or vegans that are happy about eating genetically engineered foods. But based upon many of the comments I have seen as a result of this lecture, I do feel it is worth referencing the work of Dr. Timothy J. Key that was published in the American Journal of Clinical Nutrition. Too many people have the assumption that becoming vegetarian and simply removing meat from the diet will improve one’s health. In 1999, Dr. Key and colleagues demonstrated, using a large meta analysis of 27,808 vegetarians and 48,364 non-vegetarians, that there were no significant differences between vegetarians and non-vegetarians in mortality from cerebrovascular disease, stomach cancer, colorectal cancer, lung cancer, breast cancer, prostate cancer, or all other causes combined (//ajcn.nutrition.org/content/70/3/516s.long). Now in 1999, you can be very confident that only a very, very small percentage of the non-vegetarians were eating a Paleo template, if in fact any at all. An increase in the sample size (33,883) of vegetarians in 2009 came to the same conclusions (//ajcn.nutrition.org/content/89/5/1613S.long). Now, I’m sure there was a wide variation in the diets of the vegetarians and so I understand that some vegetarians will have a better diet than other vegetarians and indeed, a better diet than many non-vegetarians. And this could include individuals that claim to be eating a Paleo diet but choose highly processed meats that would not mimic the animal protein advocated by Paleo diet researchers. But it is important to recognize that simply choosing to become vegetarian and avoiding meat consumption does not infer the health benefits that many believe come along with doing so and much can be learned by that population from the research on the negative consequences of grain, dairy, and legume consumption to help improve the diets of vegetarians as much as possible.
Coming back to Dr. Warinner’s lecture, ultimately, when one is well read in Paleolithic research, it is realized that this lecture does not make one credible statement that “debunks” the Paleo diet, not one. It would have been very interesting to watch this presentation conducted in an expert panel format where all of Dr. Warinner’s positions could have been questioned as they occurred. A format such as this would be more useful to the listener so that inaccurate positions cannot be simply thrown out to suit the argument. Perhaps the TED lectures could arrange such a panel for some lively discussion, which, I await with baited breath! Until then, it is safe to say that this presentation is way off the mark (offthemark.org).
Transcript of Dr. Warinner’s lecture, 5:11 to 8:25:
“So where does this meat myth come from? There is really two places, and one is the inherent bias in the archeological record. Bone is 80% mineral by weight, it’s going to preserve better and longer over thousands of years than delicate plant remains. But the other issue comes from some early bone biochemistry studies that were performed on Neanderthals and early people.
This bone biochemistry study is based on something called nitrogen stable isotope analysis, it’s complicated but I’m going to try and break it down. The basic idea is that you are what you eat and so we, there’s nitrogen15 and nitrogen14, heavy and light versions of nitrogen and we consume this nitrogen in our food. But there’s one important difference and that is with each step you go up to trophic hierarchy the amount of the heavier isotope increases. So if you measure the amount of heavy isotope in the bone, you can infer where that individual was on a food chain. [She shows a slide] This is an example of a generalized isotopic model and I’ve plotted where plants generally fall, then above them are the herbivores and then above them the carnivores. But one of the problems is that not all ecosystems conform to this model, there’s a lot of regional variability so if you don’t understand the region you can come to erroneous conclusions. So I’m going to give you some examples.
We can take East Africa, if we measure animals and humans, ancient humans in East Africa, we see some very strange patterns. First of all, how can a human be higher than a lion, lions only eat other animals. And then, how is this herbivore above a lion. Well it turns out that the food that you eat is not the only contributor to these isotopic values and that aridity can also have an impact. So what we’re likely seeing here is differences in water access. So let’s move out of the savanna and move into the tropical areas. Let’s look at the ancient Maya, again we see something anomalous, we see the ancient Maya lining up with jaguars. Now we know the ancient Maya had a diet heavily reliant on corn, so what’s happening here? We don’t exactly know but we think this may have to do with the way they performed agriculture and how they fertilized their crops. Now let’s go to the Pleistocene, we see some really interesting patterns here too. We see reindeer plotting very low in the range of plants, we see wolves plotting normally where he would see herbivores and we see mammoths spanning all three levels at once, plants, herbivores and carnivores. So what we think is happening here is that in very, very, cold climates animals eat unusual things and in this case we think what is happening is these mammoths are eating lichens and bark, and it’s giving them very strange values.
So if we now go to humans, ancient humans, Paleolithic humans and Neanderthals, we see that they plot in the same isotopic space as jaguar, or as uhmm, wolves and hyenas. Now that’s true but as I’ve shown if you don’t have a good control over the regional isotopic ecology you can come to an erroneous conclusion, and I think it’s premature to say this is very strong evidence of meat consumption given how very little we really know about the Paleolithic ecosystems.”