Scientists Think 1.4 Million-Year-Old Stone Spheroids Were Deliberately Crafted

In the 1960s, when scientists conducted excavations at a site dating back 1.4 million years in northern Israel, they encountered a baffling discovery - they uncovered nearly 600 stone ‘balls’ amongst other more conventional stone tools. Now, scientists have analyzed 150 of these baseball sized stones and concluded that our ancestors intentionally crafted these spheroids! They speculate that perhaps early human ancestors were driven by a desire to create symmetry and enjoy the act of craftsmanship, though the exact function remains unclear.

The findings of this study, which were published today in the latest edition of the journal Royal Society Open Science, hold the potential to provide valuable insights into the cognitive processes of ancient artisans. This is as per Julia Cabanès, a scientist at the National Museum of Natural History in Paris who was not part of the research team, but spoke to Science.

Spheroids and the Software Employed

These ball-shaped stone artifacts, or ‘spheroids’, have been unearthed at various prehistoric sites worldwide, dated roughly from the end of the Oldowan period (1.7 million years ago) to the Middle Palaeolithic period (250,000 years ago). Their existence has posed a longstanding puzzle for archaeologists – were they intentionally chipped away at with the intention of sphere-making, or were they an accidental byproduct of repeatedly smashing the stones, somewhat like ancient hammers or stone hand axes?

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Map of selected locations where stone balls (including spheroids) have been documented. Right: Map of stone ball sites in the southern Levant, including the location of 'Ubeidiya. ((Muller, A., et al. /Royal Society Open Science)

“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 the Hebrew University of Jerusalem, who conducted the study. “This takes remarkable planning and forethought, as well as a great deal of manual dexterity and skill.”

The HUJI team employed a novel method using cutting edge 3D analysis software developed by a group of scientists at the Computational Archaeology Laboratory of the university. Through this, they were able to measure surface angles on spheroids, calculate surface curvature levels, and pinpoint the center of mass of these objects, according to a press release.

With this technology, they conducted a comprehensive analysis of 150 limestone spheroids recovered from the archaeological site in northern Israel known as 'Ubeidiya’. This site is believed to have been inhabited by Homo erectus, an ancient hominin species known for its tool-making abilities.

Professor Leore Grosman, a co-author of the study was quoted by Interesting Engineering, explaining that, “ 'Ubeidiya is presently recognized as the earliest known Acheulean occurrence outside of Africa, making it a crucial location for investigating the evolution of early hominin technology.”

The 3D scans showed an accurate determination of the angles of markings present on the spheroids, allowing the scientists to reconstruct, to the best of their abilities, the process involved in crafting these objects.

Following this, an analysis of scar facets and geometry of the stones allowed a successful reconstruction of the reduction sequence of the spheroids. During this process, they identified a distinctive pattern in the spheroids from 'Ubeidiya, suggesting that there was a premeditated strategy to the craftsmanship.

Cabanès advocates for the application of this 3D analysis method to other, even older artifacts, increasing the ambit and purview of this technology. Spheroids dating back up to 2 million years have been excavated from other sites in Africa, and if these too were intentionally shaped as per the scope of the current study, it would open up a Pandora’s Box of possibilities of what our ancestors were capable of.

Study methods of measuring edge angles, center of mass and surface curvature of each stone seeking to understand how the spheroids were made and if it was intentional. (Muller, A., et al. /Royal Society Open Science)

The ‘Intentionality’ Debate: Smooth vs. Rough Tool Making

“Our results suggest that the spheroids of ‘Ubeidiya are a complex formal technology that represent a manifestation of the complex cognitive and skillful capacities of Early Acheulean hominins,” write the authors in the study. Notably, each spheroid possesses a prominent "primary surface" surrounded by smaller worked planes, implying a manufacturing process that involved the removal of a substantial stone flake followed by the careful chipping of the flattened area's edges.

Clearly, it is highly improbable that these spheres are the product of any natural processes, as they don’t possess the smooth quality that would be indicative of erosion over time. If that had been the case, they would have been akin to stones found in riverbeds that undergo extensive smoothing due to water erosion. Naturally occurring stones seldom assume a perfectly spherical shape.

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In contrast, the stones unearthed at the 'Ubeidiya site exhibit rough surfaces, consistent with handcrafting, and some of them approach near-perfect spherical forms—a feat achievable only through the deliberate efforts of skilled toolmakers.

Adding to the hypothesis around intentionality, the scientists compared these spheroids to other artifacts from this historical period, like finely crafted stone hand axes. When considered alongside these spheroids, it seems that our early ancestors possessed a love for symmetry, proportion, and aesthetics, though their purpose remains “mysterious” – they could have served a function as projectiles or had some other artistic symbolism that can only be explored in future studies.

“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.

Top image: The spheroids of 'Ubeidiya.   Source: Muller, A., et al. /Royal Society Open Science

By Sahir Pandey