Ancient Humans Turned Volcanic Rock Spheres Into Tools
For more than one million years, naturally occurring basalt rock spheres have been used by hominin species as a type of tool.
Researchers have found these tools across Pleistocene Europe, Asia, and Africa. Their potential uses range from percussion tools to hunting equipment.
These “spheres” are present at Melka Kunture, an archaeological site in the Upper Awash region of Ethiopia. Since the area was surrounded by several eruptive centers, the spheres are made of volcanic basalt, unlike others in the nearby region, which are made of limestone.
Spheres collected from eight sites were analyzed. The oldest inhabited site is called Gombore IB, and it contained nearly 5,000 stone tools, three spheres, and two fragments of an upper arm bone from a hominin species. The spheres from this site were housed at the National Museum of Addis Ababa.
The youngest sites were Garba I, II, and III. Together, they contained 22 spheres and over 7,000 lithic tools. Hominin bone fragments were found alongside the spheres, indicating that hominins collected and used these spheres.
They brought the naturally occurring spheres to the sites on purpose. Some spheres were probably transported there by water. The researchers carefully analyzed them, taking note of their size, shape, weight, and evidence of flake scars.
“The metric characteristics, shape, and orientation of pebbles transported by water have been researched and are well understood, as can be seen in previous papers,” said Dr. Margherita Mussi, the leader of the study.
“Furthermore, note that some of the sites are fine-grained deposits where the relatively heavy rock spheres are at odds with the surrounding environment, and also that the rather soft lapilli ones would have been easily crushed during water transport.”
It is believed that early hominin species specifically selected these spheres to be used as percussive tools. The hard volcanic ones were likely used to retouch lithic tools, while the soft lapilli ones were used for rubbing vegetables, hides, and other materials.
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The spheres are not traditional tools and were only recognized as tools in the first place due to markings of wear and tear.
The discovery offers new insights into how the use of tools evolved among early hominins and the way they utilized the environment to their benefit.
“It is possibly the first evidence of the use of natural shapes for varied activities, and this happened repeatedly over more than one million years of human evolution at Melka Kunture,” Mussi said.
“While hominin species were changing from Homo erectus to H. heidelbergensis, the round rocks were selected from various sources in a changing environment. In my opinion, this is good evidence of how the hominins were carefully exploiting any new resource and cleverly using them.”
The details of the new study were published in the journal Quaternary International.
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