This is according to a study published July 16, 2014 in the open-access journal
by Stephen Buckley from University of York and colleagues.
Evidence of plant consumption before the adoption of agriculture is difficult to find; such evidence is meaningful for understanding how much prehistoric people knew about the ecology and potential therapeutic properties of plants. Scientists in this study extracted and analyzed chemical compounds and microfossils from dental calculus (calcified dental plaque) from ancient human teeth at Al Khiday, a pre-historic site on the White Nile in Central Sudan, Africa. One of the five sites at Al Khiday is predominantly a burial ground of pre-Mesolithic, Neolithic, and Later Meroitic age remains. As a multi-period cemetery, it can provide us with a useful long-term perspective on any materials recovered there.
The authors chemically analyzed dental calculus samples from 14 individuals in the three different periods and found that humans ingested a certain plant, purple nut sedge, for at least 7,000 years, during both pre-agricultural and agricultural periods. As a good source of carbohydrates with potential medicinal and aromatic qualities, purple nut sedge—today regarded as a nuisance and considered to be the world's most costly weed— formed an important part of the prehistoric diet. In addition, the ability of the plant to inhibit a certain type of Streptococcus may explain the unexpectedly low level of cavities found in the population. According to the authors, the research suggests that prehistoric people living in Central Sudan may have understood both the nutritional and medicinal qualities of purple nut sedge as well as other plants.
Lead author Karen Hardy, said: "By extracting material from samples of ancient dental calculus, we have found that rather than being a nuisance in the past, the purple nut sedge's value as a food, and possibly its abundant medicinal qualities, were known." She added, "We also discovered that these people ate several other plants, and we found traces of smoke, evidence for cooking, and for chewing plant fibres to prepare raw materials. These small biographical details add to the growing evidence that prehistoric people had a detailed understanding of plants long before the development of agriculture."