The mammoth diet of Neanderthals

Stable isotope evidence from three Belgian sites

Attempts to gain insight into Neanderthal diet have been many and various over the years. Methods have included consideration of dental microwear, tooth calculus, lithic use-wear and residues, and stable carbon and nitrogen isotope data. These studies have shown that the Neanderthal diet included the consumption of large herbivores, but the extent to which smaller mammals, birds, riverine and seafood was eaten remains uncertain.

To address these issues, researchers conducted carbon and nitrogen stable isotope analyses of collagen extracted from Neanderthal remains from the Belgian sites of Goyet and Spy. Results were compared with those from extensive faunal remains from Goyet, Spy and a third Belgian site, Scladina. These included mammoth, rhino, horse, reindeer, hyena, wolf, cave bear and cave lions. The proportion of the isotopes carbon-13 and nitrogen-15 reflect an animal’s place in the food chain: the highest levels are found in carnivores.

The results show that Neanderthal isotope levels and hence diet differed from that of any carnivore, indicating that they occupied a distinct ecological niche. The overall data suggested that while predators typically preferred smaller animals such as reindeer and horse, the Neanderthal focus was on large herbivores. Mammoth was the most important source of meat, accounting for around 30 to 40 percent of the Neanderthal diet. Reindeer and rhino accounted for lesser proportions, and plant food for about 20 percent.

Reference:

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Wißing, C. et al., Isotopic evidence for dietary ecology of late Neandertals in North-Western Europe. Quaternary International, http://dx.doi.org/10.1016/j.quaint.2015.09.091 (2015).x

Meat-eating and food processing were major drivers of human evolution

Study shows how dietary changes and stone tools enabled reductions in size of teeth, jaws and gut

In comparison to earlier hominins, Homo erectus was bigger both in stature and brain size. As such, its energy requirements would have increased – but paradoxically the teeth and chewing muscles were smaller, maximum bite forces weaker and the gut size was reduced. It has long been assumed that this was made possible by increased meat consumption, slicing and pounding food with stone tools, and by cooking. However, the latter was uncommon until around 500,000 years ago. By these means, it is believed that Homo erectus and later humans reduced the both amount of chewing required for their food and workload of the gut in digesting it.

In a newly-published study, Zink and Lieberman report on a series of experiments intended to test these hypotheses. They measured chewing performance in adult human subjects fed size-standardized portions of meat and underground storage organs (roots, tubers, etc.) which are thought to have formed a major component of hominin diet. Goat meat, yams, carrots and beets were chosen for the test; goat is tougher than beef and therefore more similar to the wild game eaten by early hominins. The food was either unprocessed, processed by simple mechanical methods available in Lower Palaeolithic times (slicing and pounding), or roasted (the simplest form of cooking).

They found that the subjects were unable to chew the raw meat effectively, but slicing it resulted in substantial reductions in both the amount of chewing and bite forces required, and in smaller and more digestible meat particles were swallowed. Roasted meat required a greater chewing effort, but even smaller meat particles resulted. However, even unprocessed meat required considerably less masticatory effort than the raw USOs.

Although the advent cooking brought considerable benefits in terms of hygiene and increased energy yields, Zink and Lieberman believe that the reductions in dental size and jaw musculature observed in Homo erectus would have been made possible by the combined effects of eating more meat and mechanically processing both it and USOs. By eating a diet of one-third meat and two-thirds USOs, and slicing the meat and pounding the USOs with stone tools prior to eating, early humans would have reduced chewing by 17 percent and enabled a 26 percent reduction in bite forces.

Although it is possible that food processing and meat eating favoured evolutionary selection for smaller teeth and jaws, Zink and Lieberman believe that it is more likely that these relaxed the selective pressures maintaining robust masticatory anatomy, thus enabling selection to decrease facial and dental size for other functions such as speech production, locomotion, thermoregulation, and possibly even changes in the size and shape of the brain, so leading eventually to the modern condition of Homo. Regardless of what evolutionary factors favoured these changes, they would not have been possible without increased meat eating combined with food processing technology.

Reference:

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Zink, K. & Lieberman, D., Impact of meat and Lower Palaeolithic food processing techniques on chewing in humans. Nature (Published online) (2016).

Neanderthals ate their greens

Analysis of 60,000 – 45,000 year old coprolites provides insight into Neanderthal diet

Neanderthal dietary reconstructions have, to date, been based on archaeological evidence, stable isotope data and studies of dental calculus. These suggest that they were predominantly meat eaters, although plant foods made a contribution to their diet. Hitherto, there has been no direct evidence for an omnivorous diet.

A new study, published in the open access journal PLoS One has presented direct evidence of Neanderthal diet using faecal biomarkers, which are a valuable analytical tool for identifying diet. Researchers applied gas chromatography and mass spectroscopy techniques to coprolites (fossil faeces) from the Neanderthal site of El Salt at Alicante, Spain. The coprolites were recovered from sediments gathered from a number of levels at the site, which was repeatedly occupied by Neanderthals between 60,000 and 45,000 years ago.

The team focussed on chemical processes associated with the action of bacteria in the gut. They found a high proportion of coprostanol, which the gut bacteria produce from cholesterol and which is associated with the consumption of meat. However, they also recorded significant quantities of 5β-stigmastanol, which is associated with plant consumption.

Further tests were necessary to confirm that the coprolites were of human origin. The conversion of cholesterol into coprostanol is not unique to humans, but related molecules were also identified in proportions that ruled out other omnivores.

   

References:

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1.  Ainara Sistiaga, A., Mallol, C., Galván, B. & Everett Summons, R., The Neanderthal Meal: A New Perspective Using Faecal Biomarkers. PLoS One 9 (6), e101045 (2014).

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Link:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0101045