Ancient rocks excavated from a site inhabited by early humans around 1.4 million years ago may represent attempts to achieve perfect geometry.

Archaeologists say the limestone spheroids from the prehistoric site of Ubeidiya in Israel were deliberately shaped, and show signs of improvement the more work is done on them. This indicates that the creators had a specific goal in mind when they were carving, and that goal was very round.

This discovery doesn’t get us very close to knowing what the spheres were used for, but it does show that there was a reason for making them that way.

A team led by archaeologist Antoine Müller of the Hebrew University writes: “As they are manufactured, the spheroids do not become smoother, but become noticeably more spherical. They approach a perfect sphere, a feat that likely requires skilled skill and predetermined purpose.” Jerusalem in Israel.

“The deliberate production of sphere-like objects at Ubaidiya similarly shows evidence of the desire of Acheulean hominins to achieve deliberate geometry and symmetry in stone.”

How the researchers measured the surface angle, center of mass, and surface curvature of each of their artifacts. (Mueller et al., R. sock. Open science fiction.2023)

Spheroids are one of the fascinating mysteries of prehistoric times. They appear at sites across Africa, Asia and the Middle East dating back to about 2 million years ago, with varying degrees of sphericality. And we don’t know what they were for.

Some studies indicate that early humans used spheroids as projectiles. Other researchers speculate that they may have been used to break down marrow from bones. However, its function remains obscure, despite extensive and thorough exploration of various avenues.

Rather than study the specific function or functions that the spheres might perform, Müller and his colleagues decided to take a step back. Instead, they investigated whether the balls were manufactured on purpose, or an accidental byproduct of the manufacture of other tools.

The research focused on 150 spherical bodies that were recovered from Al-Ubaidiya. Dating at approximately 1.4 million years old, they are the oldest known appearance of the objects outside of Africa, and represent an unusually large collection from a single location.

The team ran high-resolution 3D scans, creating retinal models that they could analyze without damaging the original artifacts. Then they used software to calculate the angles on the surfaces of the spheroids, where their centers of mass were, and the curvature of the surface of each sphere. The researchers also used mathematical functions called spherical harmonics to reconstruct the shape of each sphere, and analyzed the scars on each sphere’s surface to determine how they were created.

Graphs showing the relationship between stone reduction and approximation to sphericity. (Mueller et al., R. sock. Open science fiction.2023)

According to the data, the spheroids were intentionally entangled, as their makers carefully removed material from specific points on the object’s surface. The higher the surface that is cut, the rounder the balls.

However, the rocks did not become smoother, which the researchers attribute to intention.

“Because the curvature of the surface was not related to the intensity of reduction,” Müller and colleagues write, “the abductors in Obeidiyeh did not want a smooth, nearly round object.”

“Nor did they accidentally produce a glaze by intense percussion. Rather, they seem to have attempted and approached the Platonic ideal of the sphere following their spherical shorthand sequence.”

Even without knowing what the spheroids were used for, the findings have important implications. They suggest an intentional cognitive process, and the skills to carry it out.

This means, the researchers say, that the spheroids represent a complex formal technique, and the first known attempt to impose symmetrical geometry on stone tools.

The research has been published in Royal Society for Open Science.

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