A team of researchers from the Cleveland Museum of Natural History and Kent State University propose a revolutionary hypothesis about the origin of stone tools: Early humans first used naturally sharp edges before they began to craft such tools themselves. The new theory offers a more economical and logical explanation for the emergence of stone technologies compared to previous theories.
During field expeditions in regions including Kenya and Oman, the research team discovered that naturally sharpened stones, called naturalites, occur in large quantities in the natural environment. These findings challenge prior beliefs that such sharp stones were rare in nature. The research was published in the journal Archaeometry.
"In some cases, Mother Nature produces sharp stones in quantities of hundreds, thousands, or even more," said Michelle R. Bebber, co-author of the study, according to Observador. "It's amazing... our hominin ancestors probably had natural knives readily available," Bebber added.
The researchers suggest that only after using naturally sharp stones for cutting did ancient humans experience selective pressure that led them to start knapping their own stone tools. Knapping allowed early humans to improve on nature's invention, producing stone flakes with desired characteristics instead of expending effort searching for suitable natural specimens. This evolutionary pressure pushed ancient hominids toward the next technological advancement: the deliberate knapping of stone tools according to their own design.
"This is the simplest hypothesis for the origin of hominin stone technology to date," said Metin Eren, a member of the research team. "There is no reason to produce sharp stone tools unless the need for cutting already exists," he further explained. "I don't think it was a moment of inspiration, when hominins first made a sharp stone flake intentionally or accidentally and then looked for something to cut," he added.
One scenario for the transition to stone tool production is related to limited access to resources, necessitating the artificial creation of sharp stone flakes when naturalites became scarce. This need for reliable tools may have driven early humans to develop their own methods for producing sharp edges.
Field investigations in Kenya showed that early hominin food processing sites are generally near natural sources of stone. The proximity to these resources suggests that access to naturally sharp stones played a role in their daily lives. The technology of sharp stone tools, developed over three million years, allowed early humans to exploit food resources of animal and plant origin, contributing to the increase in human brain size.
The new hypothesis proposes that, for a considerable period before early humans made their own stone tools, they initially used and relied on naturally sharp rocks produced by geological processes, such as the impact of rocks in a streambed, or biological processes, such as the trampling of rocks by animals.
The article was written with the assistance of a news analysis system.