Sorry paleo dieters, cavemen weren't exclusively meat eaters. They liked their grains too.

Researchers in Italy say they've identified the earliest evidence of food processing in Europe, a stone that was used to grind oats and other grains.

The small brown stone, rounded on one end from its use as a combination pestle and grinder, was unearthed in southern Italy in 1989 -- found inside a cave called Grotta Paglicci, near Puglia. After an initial wave of research, the stone was put away.

But two years ago, scientists at the University of Florence decided to reexamine the stone. When they washed portions of the stone with water, they found the remnants of five different types of starch grains, the most common of which were wild oats.

"The particular condition of the starch grains has led us to believe that the grains (kernels), have been subjected to a heat treatment before being crushed," researcher Marta Mariotti Lippi, a botanist at Florence, said in a press release.

Lippi and her colleagues say the ground grains were most likely mixed with boiling water and cooked, the end result of which may have been oatmeal or porridge, as even rustic breads.

The cave where the stone tool was found shows evidence of human habitation between 34,000 and 32,000 years ago. Inside the cave are murals of goats, cows, a snake and a nest with eggs.

The new research was published this week in the Proceedings of the National Academy of Sciences.