Early omnivores
Beginning in the early 2000s, Longo and her colleagues started analysing unwashed stone tools from a 28,000-year-old human settlement in central Italy called Bilancino. Patterns of wear on the sandstone tools suggest that they were used for grinding, like a mortar and pestle. The stones were also coated with several kinds of microscopic starch grains. Longo and her colleagues identified the grains based on their shape as belonging to the root of a species of cattail and the grains of a grass called Brachypodium.
The researchers also found grinding tools coated with cattail and fern residues at human sites in southern Moravia in the Czech Republic and south of Moscow, all dated to roughly 30,000 years old.
Unlike Neolithic humans, who domesticated and cultivated grains such as wheat and barley, these hunter–gatherers relied on wild vegetation. However, many of the plants found by Longo and her team were widely distributed, offering a reliable, even nutritious source of food, she says. For example, once ground and cooked, the cattail grains contain nearly as much energy as domesticated cereals, the researchers calculate.
pestle & mortar and starch grains
Grinding tools bear traces of 30,000-year-old cattail and fern (right).PNAS
Bar-Yosef says that the study proves that flour-making was common to early modern humans. "I'm pretty sure that you're going to have many more cases where there is evidence for the use of plants by humans."
Bruce Hardy, a paleoanthropologist at Kenyon College in Gambier, Ohio, expects that flour-making dates back even further than 30,000 years. "This is not isolated to a small group of people. It's a regular part of subsistence for humans," he says.
After all, humans, ancient or modern, just aren't equipped to live on a diet of meat alone. "If you get that much meat in your diet not balanced out with other nutrients, you get protein poisoning," says Hardy.
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References
1. Revedin, A. et al. Proceedings of the National Academy of Sciences advance online publication doi:10.1073/pnas.1006993107 (2010).
http://www.nature.com/news/2010/101018/full/news.2010.549.html