Early ancestors of humans 1.4m years ago deliberately made stones into spheres, according to a study – though what the prehistoric people used the balls for remains a mystery.
Archaeologists have long debated exactly how the tennis ball-sized “spheroids” were created. Did early hominins intentionally chip away at them with the aim of crafting a perfect sphere, or were they merely the accidental byproduct of repeatedly smashing the stones like ancient hammers?
Research led by the Hebrew University of Jerusalem suggests our ancestors knew what they were doing.
The team of scientists examined 150 limestone spheroids dating from 1.4m years ago that were found at the ’Ubeidiya archaeological site in the north of modern-day Israel.
Using 3D analysis to reconstruct the geometry of the stones, the researchers determined that their sphericalness was “likely to have been produced intentionally”.
The early hominins – exactly which human lineage they belonged to remains unknown – had “attempted to achieve the Platonic ideal of a sphere”, they said.
While the spheroids were being made, the stones did not become smoother but did become “markedly more spherical”, said the study in the journal Royal Society Open Science.
This is important because while nature can make pebbles smoother, such as those in a river or stream, “they almost never approach a truly spherical shape”, the study said.
Julia Cabanas, an archaeologist at France’s National Museum of Natural History, who was not involved in the research, said this meant that the hominins had a “mentally preconceived” idea of what they were doing.
That in turn indicates that our ancient relatives had the cognitive capacity to plan and carry out such work.
Cabanas said the same technique could be used on other spheroids. For example, it could shed light on the oldest known spheroids, which date back 2m years and were found in the Olduvai Gorge in modern-day Tanzania.
But exactly why our ancestors went to the effort of crafting spheres remains a mystery. Theories include that the hominins were trying to make tools that could extract marrow from bones or grind up plants.
Some scientists have suggested that the spheroids could have been used as projectiles, or that they may have had a symbolic or artistic purpose.
“All hypotheses are possible,” Cabanes said. “We will probably never know the answer.”