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Patterns of scars and angled surfaces on “spheroids” from the archaeological site of ‘Ubeidiya suggest the artifacts were intentionally crafted from limestone.LEORE GROSSMAN
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When scientists excavated a 1.4-million-year-old site in northern Israel in the 1960s, they were stumped by the presence of nearly 600 plum-size stone balls alongside more usual stone tools such as hand axes. These rocky orbs had no discernible purpose, and some speculated they may have been debris produced while making other tools. Now, researchers suggest our ancient relatives intentionally crafted these spheres, perhaps for the sheer joy of creating symmetry.
The methods behind the study—published today in Royal Society Open Science—could serve as “a valuable tool” for gaining insight into the minds of ancient craftspeople, says Julia Cabanès, a scientist at the National Museum of Natural History in Paris not involved in the research.
Ball-shaped stone artifacts, referred to as “spheroids,” have been found at numerous prehistoric sites around the globe. Their existence has long puzzled archaeologists, who disagree about how and why they were made. Some have hypothesized that they were the byproducts of other tasks, such as the making of stone hand axes. Others maintain the spheres were intentionally designed—though it’s unclear to what end.
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To help settle the debate, a team of scientists at the Computational Archaeology Laboratory of the Hebrew University of Jerusalem (HUJI) developed new, sophisticated, 3D analysis software that can measure angles on the surface of a spheroid, calculate the level of surface curvature, and determine the object’s center of mass. They used this software to analyze 3D scans of 150 limestone spheroids from the northern Israeli site, known as ‘Ubeidiya, where a species of ancient hominin toolmakers known as Homo erectus may have lived. The researchers were able to precisely measure the angles of markings found on the surface of the spheroids and reconstruct, as best as they could, the process by which artisans made them.
The ‘Ubeidiya spheroids, the authors conclude, bear the hallmarks of intentional craftwork. For example, each has a large “primary surface” surrounded by smaller worked planes, which suggests they were made by first removing a large flake of stone and then chipping away at the edges of the newly flattened area.
The stone balls are unlikely to have been created by natural processes, the authors say. If they were, the researchers argue, then their texture would be much smoother. Stones found in rivers, for example, tend to be supersmooth because of water erosion. Their shapes, however, are almost never truly spherical. The stones found at ‘Ubeidiya, by contrast, have rough surfaces—as one might expect from hand crafting—and some of them are near-perfect spheres, as only a toolmaker could create.
“It appears that hominins 1.4 million years ago had the ability to conceptualize a sphere in their minds and shape their stones to match,” says lead author Antoine Muller of HUJI. “This takes remarkable planning and forethought, as well as a great deal of manual dexterity and skill.”
Other artifacts from this period include elegantly constructed stone hand axes. Considered alongside these spheroids, the new work suggests these early toolmakers had an appreciation for both symmetry and beauty, the authors say.
Even so, the new results don’t solve the mystery of why these ancient toolmakers shaped these spheroids in the first place. Their purpose, Muller says, remains “enigmatic.”
Naama Goren-Inbar, an HUJI archaeologist, is skeptical. She notes that numerous scars on the surface of the ‘Ubeidiya spheroids make it impossible to know what the objects may have looked like at earlier stages of creation. The researchers might have gotten a clearer picture if they compared comparatively more spherical artifacts with less spherical ones, she contends, which may represent objects that were abandoned in the middle of the manufacturing process. Instead, the authors lumped all the spheroids into the same category, which Goren-Inbar says is a mistake.
Cabanès, for her part, wants to see the 3D method applied to other, even older artifacts. Spheroids up to 2 million years old have been excavated from sites in Africa. If the authors’ analysis reveals that these objects were also intentionally shaped—and if their method can be believed—it would suggest that humans have had an eye for symmetry, and the ability to create it, for a very long time.
