A recent paper (Weyrich et al., 2017) received an enormous amount of publicity, with a claim that Neandertals in El Sidron, Spain were vegetarians. Some media headlines could even be interpreted as suggesting that the Paleo Diet was vegetarian.
The Paleolithic is a worldwide phenomenon that lasted for nearly 3 million years so a reconstruction of a Paleolithic Diet is bound to be a monumental task. Say you have a time machine and you embark on the project. How many Paleolithic groups would you consider to be a satisfactory sample size? For how long would you stay with each group as they move between sites with the seasons? How many people would you follow at each group? How would you measure their food consumption? What geographical area would you cover?
Would you start with H. sapiens 200,000 years ago, or with H. erectus 1.9 million years ago? Would you also include Neandertals, who were a contemporary Homo species to H. sapiens, until they went extinct 40,000 years ago?
Whatever you decide, it is quite clear that in order to describe “The Paleolithic Diet”, if there is a typical one, you’ll need to collect thousands and thousands of data points. In reality we don’t have a time machine so we have to collect and interpret many types of indirect evidences of what humans ate. In an AHS13 talk, I described some 10 scientific disciplines which contribute evidence that can be used to reconstruct a Paleolithic diet, and that list is by no means complete.
Laura Weyrich (and her team) had only 2 data points of dental plaque, not even of modern humans or archaic H. sapiens, but she felt quite able to describe the findings to NPR as follows: “It is very indicative of a vegetarian diet, probably the true Paleo diet.” On the basis of other interviews I believe she may have been misquoted, or got carried away a little. In the paper, Weyrich et al. describe the diet of other Neandertals from Spy, Belgium, as exclusively carnivorous.
Weyrich’s team members have every reason to be excited about their findings and about the potential for their method. Dental plaque record macroscopic as well as microscopic scale events at the same time. To quote: “Oral bacterial species, viral and fungal taxa, remnant food debris, and disease causing microorganisms can and do appear in ancient plaque, providing information on the diet, health, diseases, microbes, environment, and perhaps even cultural affinity of an individual.”.
However, in science, the details rule. Scientist spend a lifetime pondering and checking details and then come up with hypothesis or try to shake somebody else’s hypothesis. So, beside the easy conclusion that two samples of Neandertals from one site cannot describe a diet of Paleolithic humans, I would like to argue that they cannot even describe the diet of these two individuals, let alone Neandertals in general and definitely not H. sapiens.
Weyrich et al. found only plant residues in teeth plaque samples from two individuals from the Neandertal site of El Sidron in northern Spain.
Weyrich herself admits that “we don’t know if we are looking at their last meal or random food debris from the last ten years”. Weyrich will probably agree with Anne Stone of Arizona State University who said to The Atlantic: “I don’t think we really understand how dietary DNA is incorporated into plaque. Do some types of food get incorporated more than others, or is it random? How much do you need to eat of something before it shows up? “
One thing we do know about teeth plaque accumulation – its buildup is accelerated when carbohydrates form a large part of the diet (Lieverse, 1999). Dental remains are available for eleven individuals out of the thirteen that were found in El Sidron (Estalrrich et al., 2017) so we have to wander if only teeth from two individuals had enough plaque to sample, what does it say about the amount of carbs in the diet of the other nine El Sidron Neandertals?
We don’t know if meat residues are consistently incorporated into teeth when carbohydrates are consumed. Even when meat is consumed, the incorporation of meat may be under-represented. In Spy, Belgium, Weyrich et al. report that only woolly rhino and wild sheep’s residues were found in the plaque, but it is highly unlikely that these were the only animals that the Spy Neandertals acquired. A study of stable isotopes (Wissing et al., 2015) found that mammoth was the most important species in Spy Neandertals’ diet, yet its residues are not found in the sampled plaque.
Another group of researchers (Estalrrich et al., 2017) used another feature of the El Sidron teeth, microwear, to elucidate their diet. Their method relies on comparison with microwear in teeth of recent hunter-gatherer groups, whose dietary meat/plants composition is supposedly known. They conclude that the El Sidron group’s diet was “mixed (in term of meat/plant foods M.B.) and included substantial amounts of plant foods. Neandertal microwear studies are cited in the Weyrich et al. paper and the Atlantic in support of Weyrich et al.’s findings, although “mixed diet” can hardly be considered as “vegetarian”. However, looking into the reference papers (Sealy et al., 2006; Erlandson et al., 2009) that the microwear researchers (Estalrrich et al., 2017) provide to described the diet of the comparison groups, I couldn’t find any mention of a plant component in the diet. My interpretation of these two papers is that the comparison groups ate a diet high in seafood (Santa Cruz Chumash) and mixed seafood and meat (S. Africa Cape Khoe-San). In other words, the teeth microwear analysis of the eleven El Sidron Neandertals (including the two “vegetarians”) do not support a conclusion of a vegetarian diet for these people, quite the contrary. There are more issues with the El Sidron situation but I will leave it for some other time.
So, if we don’t have a time machine, will we ever have a solid hypothesis of what was the Paleolithic Diet? I believe we will, but the main support for that hypothesis will not come from the archaeological record. The archaeological record is always anecdotal, as it is in the case of El Sidron. If the question is phrased a little differently, namely: “did the Homo evolve to become a specialist (carnivore) or a generalist (omnivore)?”, large part of the answer can be found, stored in our biology. Archaeology and other scientific disciplines can then complement the picture.
Just a small example: people from groups with a high consumption of carbohydrates have a high number of AMY1 gene copies, in order to secure high levels of saliva amylase. Nenadertals were so far found to have the lowest level of two copies (Inchley et al., 2016). Consequently, it seems that they were not adapted to consume more than moderate quantities of carbohydrates, let alone be vegetarians.
Debunking is not a pleasant way to pass the time so I would like to finish on a positive note. My multidisciplinary investigations support a human evolution towards specialization in carnivory. Cordain concluded in his (2000) paper that “whenever and wherever it was ecologically possible, hunter-gatherers consumed high amounts (45–65% of energy) of animal food”. Since Cordain studied recent ethnographic records, it can be safely concluded that prior to the megafauna extinction and the spread of agriculture it was ecologically possible to consume high amounts of meat just about everywhere. And according to what I found so far, that’s what people did.
Erlandson JM, Rick TC, and Braje TJ. 2009. Fishing up the Food Web?: 12,000 Years of Maritime Subsistence and Adaptive Adjustments on California’s Channel Islands1. Pac Sci 63(4):711-724.
Estalrrich A, El Zaatari S, and Rosas A. 2017. Dietary reconstruction of the El Sidrón Neandertal familial group (Spain) in the context of other Neandertal and modern hunter-gatherer groups. A molar microwear texture analysis. J Hum Evol 104:13-22.
Inchley CE, Larbey CD, Shwan NA, Pagani L, Saag L, Antão T, Jacobs G, Hudjashov G, Metspalu E, and Mitt M. 2016. Selective sweep on human amylase genes postdates the split with Neanderthals. Sci Rep 6.
Lieverse AR. 1999. Diet and the aetiology of dental calculus. Int J Osteoarchaeol 9(4):219-232.
Sealy J, Aldenderfer M, Barham L, Pearson J, Kelly R, Marean C, Wadley L, and Sealy J. 2006. Diet, mobility, and settlement pattern among Holocene hunter‐gatherers in southernmost Africa. CurrAnthr 47(4):569-595.
Weyrich LS, Duchene S, Soubrier J, Arriola L, Llamas B, Breen J, Morris AG, Alt KW, Caramelli D, and Dresely V. 2017. Neanderthal behaviour, diet, and disease inferred from ancient DNA in dental calculus. Nature.
Wissing C, Rougier H, Crevecoeur I, Germonpré M, Naito YI, Semal P, and Bocherens H. 2015. Isotopic evidence for dietary ecology of Late Neandertals in North-Western Europe. Quat Int 10.