Somewhere between 50-40,000 years ago, anatomically modern humans overtook Neanderthals and other archaic humans, spreading out all over Eurasia.
That shift has mostly been attributed to a dramatic and sudden “revolution” called the Middle-Upper Paleolithic cultural transition, where modern humans improved their tool-making, found new and different sources of food, took to the seas, and expressed themselves through ornaments and cave art. Now, a study published Wednesday in Nature Communications has challenged this narrative, instead implying that this “revolution” was more of a gradual and complex process.
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Researchers came to this conclusion by analyzing how productive ancient humans were when it came to turning rocks into tools during a 50,000-year span between the Late Middle Paleolithic (69,000 years ago), through the Upper Paleolithic, to the Epipaleolithic period (15,000 years ago). The tools came from five sites across the western Hisma Basin in southern Jordan.
Specifically, researchers quantified the ratio between the length of a particular stone tool’s cutting edge with the mass of the stone as a whole. The more cutting-edge length per mass of stone, the more efficiently early humans used the raw stone material. “Stone raw material, like flint, is not everywhere. It needs to be procured from certain sources,” the study’s lead author, Seiji Kadowaki from Nagoya University in Japan, told Motherboard in an email. “So, more economical consumption of stone raw material reduces the cost for the procurement of raw material.”
Kadowaki said they chose this metric because they needed a way to compare very different types of stone tools in a systematic way. “Because stone tool forms and their production technology changed and varied from the Middle Paleolithic to the Upper Paleolithic, the classification system for stone tools differs between the two periods. Thus, it is difficult to have consistent criteria for comparison of the two periods,” he told Motherboard in an email.
He and his colleagues noticed that modern humans became more productive not before or at the beginning of the Middle-Upper Paleolithic cultural transition, but after they’d already started to spread out into new geographical areas in the Early Upper Paleolithic. “In terms of the productivity of cutting-edge length, its development does not simply coincide with the timing of the dispersal of modern humans.”
Much of this shift came down to the stones humans used to make tools becoming smaller and lighter. This was probably because around the same time, humans started developing bladelets—small, long, symmetrical stone tools probably used as spear- or arrowheads.
These technological changes came with a shift from humans being more mobile hunter-gatherers to having slightly more stable base camps. Many of the sites researchers looked at were small, with a few hearths—typical for more wandering groups. Some however were “more intensive occupations” where people would stay for longer periods of time. Under this new system, people may have carried around smaller, more portable blades or partially-made ones that they could use to cut up food stored at these base camps.
The latest findings agree with other studies that have been published in recent years, which also argue that the so-called revolution was actually a slower, multi-step process.
Although the latest study is specific to archeological finds in Jordan, the authors say it serves as a working hypothesis for other places worldwide, including Europe and Central-North Asia where archeologists have seen similar patterns in tool evolution.
Kadowaki also says they need more evidence from other sources before they can definitively paint a new picture of how stone tools evolved. “We need to look at other aspects of stone tools as well as other archaeological records to better understand the technological behaviors and their development at the Middle-Upper Paleolithic transition.”
