Over the years, excavators have discovered several artefacts which ancient humans used in their daily lives. For almost two million years, ancient humans crafted stones into hand-size balls but researchers were not sure about their use.

But after so many years, as per a new study, the scientists know that ancient people used these as tools to get the nutritional marrow from animal bones. In easy words, if the bones are imagined as cans of soup, then these round tools were used as can openers.

The ancient tool to extract bone-marrow

For decades archaeologists wonder how ancient humans used these round stone balls. But at last, they have found the answer as the lead researcher of the new study Ella Assaf, a postdoctoral researcher in the Department of Archaeology and Ancient Near East Cultures at Tel Aviv University in Israel has revealed that "Our study provided evidence, for the first time, regarding the function of these enigmatic-shaped stone balls that were produced by humans for almost 2 million years."

Stone balls
a) Large size dolomite SSB; b) Medium-size limestone SSB; c) Medium-size flint SSB. Assaf et al. PLOS One, 2020

The excavators have found these stone balls in some ancient sites in the world such as in Africa, Europe and Asia. But the archaeologists were clueless about their use, Assaf told the Live Science. However, it was revealed when that the team of researchers led by Assaf came across 30 stone balls in Qesem Cave in Israel where ancient humans used to live from 400,000 to 200,000 years ago, they started their search for understanding the use of these artefacts.

Among these 30 stone balls, 29 of them were made of either limestones or dolomite rock. As per Assaf, other tools found in the same site were innovative for their time, while the stone balls represent very old technology. In addition, the lead m researcher said that their presence in Israel's cave represents "their latest and last appearance in the Levant [the lands immediately east of the Mediterranean]."

Solving the mystery of ancient stone balls

Ancient stone tool
A large dolomite SSB used for bone breaking in order to extract the marrow (performed by J. Rosell). Assaf et al. PLOS One, 2020

It should be noted that to understand the use of these stone balls Emanuela Cristiani, an archaeologist at Sapienza University in Rome and a senior researcher along with her colleagues examined the stone balls microscopically through which they found wear marks and organic residues. This finding indicated that the stone balls were used by the ancient people who were the inhabitants of Israel's Qesem Cave, to break animal bones and extract the nutritional marrow.

The international team of researchers conducted two experiments to confirm the idea behind creating such a tool. First, they used cobblestones- naturally rounded stones larger than pebbles- to break apart bones and in the second experiment, they used tools to shape their own stone balls and then tested them on animal bones. Later, they understood that the shaped stone tools were much more efficient than the natural ones to break the animal bones to get the bone-marrow. Finally, a microscopic analysis gave a conclusive result.

Assaf said, "These tools provide a comfortable grip, they don't tend to break easily, and you can rotate them and use them repetitively since they have multiple ridges. These high ridges help to break the bone in a 'clean' way, and you can extract the marrow relatively easily."

During the experiment the scientists noticed that breaking the bones caused marks on the modern replicas that were similar to the archaeological traces on the ancient stone balls which confirmed that "Our preliminary assumption that these items were indeed used to extract bone marrow," said Assaf.