June 26, 2014
Neanderthal Diet Included Vegetables
Brett Smith for redOrbit.com - Your Universe Online
While popular culture may have conditioned us to think of Neanderthals as mindless meat-eaters, a new study has shown that earlier humans probably ate more plants, tubers and nuts than previously thought.
Published in the journal PLOS ONE, the new study is based on an analysis of fecal remnants discovered in a known site of Neanderthal occupation in southern Spain known as El Salt. The analysis of five samples indicated that Neanderthals did eat a lot of meat – but they also could be considered omnivorous.
"We have passed through different phases in our interpretation of Neanderthals," said study author Ainara Sistiaga, a graduate student at the University of La Laguna in Spain, in an MIT statement.
"It's important to understand all aspects of why humanity has come to dominate the planet the way it does," added co-author Roger Summons, a professor of geobiology at MIT. "A lot of that has to do with improved nutrition over time."
Earlier attempts to determine the diet of Neanderthals, such as analyzing bone fragments for carbon and nitrogen isotopes, have proven inconclusive thus far. Recent research has identified plant microfossils trapped in Neanderthal teeth, but Sistiaga said Neanderthals may not have eaten plants directly – instead consuming them from the stomachs of their prey.
"Sometimes in prehistoric societies, they used their teeth as tools, biting plants, among other things,” she added. “We can't assume they were actually eating the plants based on finding microfossils in their teeth."
In the new study, the researchers excavated small samples of dirt from distinct layers at the El Salt site and analyzed the samples at MIT. The soil samples were ground into a powder and several solvents were then used to draw out any organic matter from the sediment – particularly biomarkers that would indicate if the fecal remains came from humans.
The team first looked for signs of coprostanol, a lipid developed when the gut processes cholesterol, which comes from animals. An explicit level of coprostanol would show that the sample came from a human. The team also looked at the proportions of coprostanol to 5B-stigmastanol, a compound created from the breakdown of plants.
While each fecal sample held mostly coprostanol, two samples also held biomarkers of plants, which Sistiaga said points to a noteworthy plant intake. Because there is more cholesterol in meat than there is phytosterol in plants, it would take a considerable plant intake to generate even a small quantity of metabolized phytosterol.
"We believe Neanderthals probably ate what was available in different situations, seasons, and climates," Sistiaga said.
The study team plans to use similar geochemical techniques, along with micromorphological analysis, to study soil samples in Olduvai Gorge, Tanzania — a 1.8-million-year-old site where some of the earliest humans are thought to have lived.
"We're working in a micro context," Sistiaga said. "Until now, people have carried out residue analysis on pots, tools, and other objects, but 90 percent of archaeology is sediment. We're opening a new window to the information that is enclosed in Paleolithic soil and sediment."
Image 2 (below): El Salt archeological site. Credit: Ainara Sistiaga