Did early humans aspire to create perfect spheres out of limestone? What for?
"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. ..."
From the abstract:
"Spheroids are one of the least understood lithic items yet are one of the most enduring, spanning from the Oldowan to the Middle Palaeolithic. Why and how they were made remains highly debated. We seek to address whether spheroids represent unintentional by-products of percussive tasks or if they were intentionally knapped tools with specific manufacturing goals. We apply novel three-dimensional analysis methods, including spherical harmonics and surface curvature, to 150 limestone spheroids from ‘Ubeidiya (ca 1.4 Ma), presently the earliest Acheulean occurrence outside of Africa, to bring a new perspective to these enigmatic artefacts. We reconstruct the spheroid reduction sequence based on trends in their scar facets and geometry, finding that the spheroid makers at ‘Ubeidiya followed a premeditated reduction strategy. During their manufacture, the spheroids do not become smoother, but they become markedly more spherical. They approach an ideal sphere, a feat that likely required skilful knapping and a preconceived goal. Acheulean bifaces are currently thought to represent the earliest evidence of hominins imposing a premeditated, symmetrical shape on stone. The intentional production of sphere-like objects at ‘Ubeidiya similarly shows evidence of Acheulean hominins desiring and achieving intentional geometry and symmetry in stone."
The limestone spheroids of ‘Ubeidiya: intentional imposition of symmetric geometry by early hominins? (open access)
Figure 1. Left: A map of select sites where stone balls (including spheroids) are documented. Right: A map of sites with stone balls in the southern Levant, including the location of ‘Ubeidiya.
Figure 2. Methods of measuring edge angles, centre of mass and surface curvature. (a) The method of calculating angles on the spheroids, using the Angle Between Surfaces function of the Artifact3-D program. The red and blue dots represent coordinates comprising the angle calculation on two different surfaces. (b) An example spheroid's minimum bounding box (dashed lines) as well as the location of its centre of mass (CoM; red circle) and centre of bounding box (CoBB; blue cross). (c) Surface curvature values shown with heatmaps of example spheroids. Regions of higher curvature are shown in brighter colours.
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