What Makes Us Human

And one percent Neanderthal

The Neanderthal or the Tiger

Why do people imagine human ancestors as carnivores?

The most popular response from archaeologists I know to the news that Neanderthals ate plants has been "so much for the Palaeolithic diet".

I am not convinced that any demonstration of the real diet of our ancestors will have an appreciable effect on a modern craze that has its roots less in knowledge of the past and more in anxiety about the present.

If debunking the meat-eater image was all it took, then we should have seen the Palaeo diet cast aside when studies of starch grains stuck to the teeth of ancient hominids showed that plants formed part of their diet.

http://commons.wikimedia.org/wiki/File:ISHERB_Caveman.JPG
Science magazine argues that even after these findings, there was still a question open: how big a part did plants play in Neanderthal diet?

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That, they suggest, has now been addressed by Ainara Sistiaga, Carolina Malliol, Bertila Galván, and Roger Everett Summons, in a study published in the journal PLOS One. For a change, I don't need to summarize the research, because the article was published open access-- so any reader can download and read it.

The researchers found evidence that Neanderthals who lived in Spain's El Salt site between 60,000 and 40,000 years ago metabolized both animal protein and plants.

Archaeology magazine online notes that not everyone is convinced of the new findings:

Critics would like conclusive evidence that the feces came from Neanderthals, however.

Yes, that's right: feces. As Science explained

the team was able to detect the chemical byproducts created by bacteria in the gut in the digestion of cholesterol from meat, as well as sterols and stanols, which are lipids in plants that are similar to cholesterol. The tests revealed that the poop “clearly” contained high proportions of cholesterol and coprostanol from eating meat, but it also included significant plant sterols that “unambiguously record the ingestion of plants”.

The research team adapted techniques used to trace fecal contamination in modern drinking water, and applied them to tiny traces of excrement in the site. For critics, that opens the possibility that the material came from some other animals that used the same area.

The researchers argue that one of the chemical traces-- coprostanol-- is produced when primates digest meat, but not when other carnivores likely to be in the area do. They also identified parasites they say point to primate hosts, presumably the local Neanderthal population.

So, while there will continue to be scholarly debate, the new findings bring us closer to seeing Neanderthals as having dietary habits like modern humans.

Which raises the question: why did we ever think otherwise? Who started the story that Palaeo-humans were primarily carnivorous, and how did Neanderthals, in particular, get tagged as "obligate carnivores"-- a term applied most familiarly to house cats, in explaining why they absolutely must have a meat-centered diet?

There are two kinds of answers here. The scholarly one would emphasize initial interpretation of the results achieved by researchers using bone chemistry (isotopic studies) to assess the sources of dietary protein in Neanderthal skeletal remains.

At first, these studies were interpreted as showing preferences for large grazing animals, rather than marine sources (fish) as sources of protein, leading to speculation that Neanderthals failed to survive because their protein preferences were too narrow.

In fact, the principal researcher in this field demonstrated that environmental changes led to differences in isotope measures for the same animals when they were available to Neanderthals and to early modern humans, so that the same dietary protein source would yield different isotope signatures.

More fundamentally, of course, finding that the sources of protein were particular kinds of animals (and not high protein plants) doesn't tell us whether other plants were part of the diet, providing carbohydrates and calories.

In other words: there are a lot of variables to account for in trying to reconstruct ancient diet. The work is painstaking, and it is probably premature to jump to conclusions.

But that is only one kind of answer.

The second would have to address why people in general (including journalists) want so very very badly for Neanderthals to have been absolutely different than modern humans. Why do we imagine Neanderthals as more like tigers than like people?

The more anthropological research is carried out, the less clear are once promoted distinctions between Neanderthals and modern humans. The classic image of Neanderthals as hunched over, with receding forehead and chinless jaw, reproduces an early, flawed visualization based on one, anomalous, skeleton.

Neanderthals were short and stocky, typical of human populations in cold, dry environments. Neanderthal brains are absolutely larger than those of modern humans, although the differences are primarily related to body size, and imply overlap with modern humans. Studies of ancient Neanderthal and modern human genomes suggest that there was some degree of gene flow between the two populations.

It is undoubtedly more comfortable for modern humans if the extinction of Neanderthals can be blamed on a presumed primitive nature. While most of the evidence makes it hard to argue for primitiveness, if Neanderthals were carnivorous, that would be a sharp difference with our modern, omnivorous selves.

Otherwise, we may need to face the facts: human populations do not always survive.

Especially when faced with the effects of one dangerous animai: our own species.

Rosemary Joyce, Ph.D., is a professor of anthropology at UC Berkeley.

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