Archaeologists have been scratching their heads for decades, trying to figure out the purpose of tens of thousands of roughly hewn limestone balls strewn around areas where early humans lived. Some are from as early as 2.5 million years ago, and they’re found nearly everywhere that people existed.
What were they used for? Were these small balls made intentionally, or were they a byproduct of some other tool?
For the first time, researchers from Hebrew University have used new 3D mapping technology to determine that early humans purposefully carved these limestone spheroids, moving one step closer to cracking the code to these mysterious orbs.
The spheroids first appeared in East Africa during the earliest part of the Stone Age, the Oldowan era, dating back some 2.5 million years. These carved rock balls spread across northern Africa, through the Middle East and Europe, and were continually produced until the Middle Paleolithic Age, some 30,000 years ago. They’re the most prolific type of artifact found at Stone Age archaeology sites, but no one has been able to determine why they’re there or what their purpose was for the early humans who inhabited these sites.
Researchers from Hebrew University, in collaboration with researchers from Tel Hai College in northern Israel and Rovira i Virgili University in Spain, studied a collection of 150 limestone spheroids from the ‘Ubeidiya archaeological site near the Dead Sea. The ‘Ubeidiya site is significant because it contains the earliest known evidence of humans during the Acheulian period outside of Africa. Acheulian refers to a time during the Paleolithic period, some 1.7 million years ago to 200,000 years ago, when early humans mastered the art of creating stone tools, especially hand axes and cleavers. The ‘Ubeidiya spheres were carved around 1.4 million years ago.
Using cutting-edge 3D analysis methods, including spherical harmonics and surface curvature, they determined that early humans purposefully carved the spheres using a “premeditated reduction strategy,” which means that the humans purposefully chipped off parts of the stone to create a spherical object, a process called knapping.
“We had noted that almost all of the spheroids from ‘Ubeidiya, even the almost perfectly spherical ones, still preserved a flat area somewhere on their surface,” Antoine Muller, a PhD candidate at Hebrew University, said in an email. “The spherical harmonics analysis helped us identify these surfaces and confirm that this was a repeated pattern, not just something in our imaginations. These flat surfaces likely helped them shape the spheroids by serving as a surface that could be struck to remove other parts of the artifact.”
Muller was the lead author of the article about the ‘Ubeidiya spheroids published Wednesday in the Royal Society Open Science. He is part of the Computational Archaeology Laboratory of the Hebrew University of Jerusalem, directed by Prof. Leore Grosman.
The researchers’ dataset is available online to help other archaeologists studying spheroids in other parts of the world. The ‘Ubeidiya spheroids are about 1 million years younger than the spheroids discovered in some parts of eastern Africa. However, the breakthrough understanding that these spheroids were purposefully created could revolutionize the way archaeologists look at these orbs around the world.
“If similar intentional shaping can be demonstrated on Oldowan spheroids, this would likely represent the earliest evidence of hominins imposing a desired symmetrical geometry on their tools,” the researchers wrote in the article.
The 3D mapping is an important first step to understanding these mysterious and widespread spheres, but researchers still have a long way to go. “Unfortunately, it is still unclear what the spheroids may have been used for,” said Muller. “Narrowing down their functionality will require a lot more work.”