The popular image may be of Stone Age people gnawing on a chunk of woolly mammoth, but new research indicates their diet may have been more balanced after all.
Many researchers had assumed people living in Europe thousands of years ago ate mainly meat because of bones left behind, and little evidence of plant food.
Now, new findings indicate grains were part of the diet at ancient sites in Italy, Russia and the Czech Republic, researchers report in Tuesday's edition of Proceedings of the National Academy of Sciences.
The team led by Anna Revedin of the Italian Institute of Prehistory and Early History in Florence found grinding stones, similar to a stone and pestle, with remains of grains at the sites.
The three sites were all dated to about 30,000 years ago and the residues appear to originate mainly from cattails and ferns, which are rich in starch and would have provided a good source of carbohydrates and energy.
But "a large number of plant families are likely to have been involved in the diet," the researchers said.
Peeling and grinding the roots would also have allowed people to produce a dried flour which could be stored and cooked later, to compensate for seasonal changes in food availability, the researchers said.
The remains were found at the archaeological sites of Bilancino II in the Mugello Valley of Italy; Kostenki 16 (Uglyanka), in the Pokrovsky Valley, Russia; and Pavlov VI on the slopes of the Pavlov Hills in southern Moravia, Czech Republic.