Mysterious limestone spheres - ancient and mysterious stone remnants - have puzzled archaeologists for years. These stone balls date from the Ordovician to the Middle Paleolithic, but the exact cause of their creation remains a subject of ongoing debate. Recently, researchers from the Laboratory of Computational Archeology at the Hebrew University of Jerusalem, in collaboration with experts from the Tel Hai Institute and the University of Rovira-i-Virginia, delved deeper into the secrets of these puzzling objects, potentially uncovering clues to the intentions and skills of early humans in making them.

New research shows that ancient limestone spherical stone tools were deliberately crafted by early humans with advanced skills, challenging previous views. The study, which used three-dimensional analysis, suggests that these spherical stone tools may represent the earliest known examples of intentional symmetry in stone tool making. Image source: Muller et al.

Spherical stone tools are one of the most enduring but least understood archaeological artifacts, often thought to be a by-product of striking missions. However, the research team's study challenges this conventional view. The central question of the study is whether these globules were unintentional by-products or intentionally crafted tools for a specific purpose.

To answer this question, the researchers used state-of-the-art three-dimensional analysis methods, including spherical harmonics and surface curvature, to analyze 150 limestone spheres from the archaeological site of Ubeidiya, which date to approximately 1.4 million years ago. The methods were developed at the Hebrew University Computational Archeology Laboratory, directed by Professor Leore Grosman. Ubedia is currently considered the earliest known Acheulean site outside Africa and is therefore an important site for studying the evolution of early ape technology.

The research team carefully reconstructed the spherical reduction sequence based on the observed changing trends in scar section and geometry. Their findings revealed a remarkable pattern: the spherical stones of 'Ubedia' were crafted following an intentional reduction strategy. Contrary to the idea that spheres are an accidental byproduct, spheres do not become smoother during the manufacturing process; instead, they become noticeably more spherical. This transformation into an ideal sphere requires extraordinary tapping skills and a clear preset goal.

The discovery challenges existing ideas about the capabilities of early great apes and their relationship to technology. While the bifacial stone tools of the Acheura are traditionally considered the earliest evidence of humans intentionally creating symmetrical shapes in stone, Ubedia's intentionally crafted spherical objects equally show that these early humans desired and achieved intentional creation of geometric shapes and symmetry in stone. Spherical objects of slightly earlier date have also been found at sites in Africa. If such intentionality could be demonstrated there as well, it would be the oldest evidence that humans desire and achieve symmetrical shapes in stone.

The team's study opens new avenues into understanding the cognitive abilities and technological achievements of our distant ancestors. It also raises questions about the purpose and significance of these spheres in the daily lives of early humans.