Grinding stones found in archaeological sites suggest that prehistoric man may have eaten bread at least 30,000 years ago in Europe, researchers said.

The study, published yesterday in the Proceedings of the National Academy of Sciences, suggested that processing starch grains, possibly grinding them into flour, was a widespread practice across Europe, contrary to popular belief that the Paleolithic man was primarily a meat eater.

Grains recovered from grindstones and pestle grinders at three sites in Italy, Russia and the Czech Republic appeared to come mostly from starchy cattails and ferns, which researchers said would provide a significant source of carbohydrates and energy.

"It's like a flat bread, like a pancake with just water and flour," said Laura Longo, a researcher on the team from the Italian Institute of Prehistory and Early History.

"You make a kind of pita and cook it on the hot stone," she said, describing how the team replicated the cooking process. The end product was "crispy like a cracker but not very tasty," she added.

In order to be properly digested and realise its full nutrient value, the flour would have to be cooked after undergoing multi-step processing, including root peeling, drying and grinding into a flour likely usable for making flatbread or cakes.

For their study, researchers analysed traces of wear and residue on grindstones and other tools by microscope, and conducted experimental reconstruction of how the tools functioned.

These findings also suggest that the use of flour is older than previously believed. Before these grinding stones were found, it was believed that 20,000-year-old grinding stones found in Israel were the earliest evidence of humans using flour.