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OLORGESAILIE BASIN, Kenya — Between 300,000 and 320,000 years ago, in what archaeologists and paleontologists refer to as the Middle Stone Age, early humans began trading with other groups and communicating using symbols, according to three studies published March 15 in Science journal, pushing back the previously believed timeline for such behaviors.
Long-term changes in climate and environment may have contributed to these behavioral adaptations, said Tyler Faith, curator of archaeology at the Natural History Museum of Utah and assistant anthropology professor at the University of Utah, who helped co-author the research, which was a collaborative effort from scientists around the world.
“Unique behaviors associated with our species may be rooted in really dynamic climatic changes in East Africa,” Faith told KSL.com.
The discoveries are the latest update on paleontological research in the Olorgesailie Basin in Kenya that scientists have been looking at for decades. Rick Potts, director of the Human Origins Program at the National Museum of Natural History, has been working in the region since the early ’80s, Faith said. The area is known for having an archaeological and paleontological record that “goes back maybe 1.2 million years or so,” Faith said.
Through a series of excavations, Faith said his colleagues found evidence of a major change in human behavior at about 300,000 years ago that “corresponds with earliest fossil evidence for our species (Homo sapiens).”
From about 1.8 million years ago to as recent as 200,000 years ago, human ancestors have been using cutting tools and hand axes, which Faith said is “the longest-lived technology ever.” New discoveries in the Olorgesailie Basin, however, indicate use of a “very different technology” during the Middle Stone Age, including tools with shaper points that “were probably hafted and used as projectile weapons,” according to Faith.
The research published in March also points to evidence of early humans carrying colored stones long distances and exchanging them, possibly pointing to a “prehistoric trade network,” Faith said, adding that obsidian rocks and volcanic glass were discovered in areas where they aren’t normally found.
Another discovery is of ocher, a yellow clay pigment, used to decorate the body, indicating usage of pigment “as a means of symbolic expression” and to mark differences between tribes, Faith said.
These are “a fleet of behavioral changes, technological changes, and other things that may be indicative of symbolic expression … all at about 300,000 through 320,000 years ago,” Faith said.
“This change to a very sophisticated set of behaviors that involved greater mental abilities and more complex social lives may have been the leading edge that distinguished our lineage from other early humans,” ” Potts of the National Museum of Natural History, who headed the research, said in a written statement.
Which leads to Faith’s research contribution: exploring what drove these behavioral changes in early humans. Looking at shifts in climate over geological timescales, Faith found that it is “perhaps very likely” that the human behavioral changes are related to “high amplitude climate shifts over the long term.”
The behavioral changes correspond “with a configuration that would’ve translated to very climate and environmental variability in East Africa,” Faith said. As is noted in the study, Middle Stone Age sites are associated with a “dramatically different faunal community, more pronounced erosion-deposition cycles, tectonic activity and enhanced wet-dry variability.”
Early Middle Stone Age sites “are associated with a massive turnover in the large mammal faunas,” said Faith. “A lot of critters that used to be very common become extinct, and they’re replaced by new immigrants from elsewhere or, in some cases, new species not known anywhere else.”
However, the study is not the first to point to environmental and climate shifts as contributing to behavioral changes. “That is probably something that has dominated human origins research since I got into it,” Faith said, and “well before then.”
The biggest takeaway from the research is not the discovery of the “oldest example of something,” which “is fine until 10 years from now when we have a new oldest example,” Faith said. Rather it is assessing the idea that “extremely high climate variability in East Africa may have been a very important driver of behavioral innovation in our species.”
The study Faith co-authored is one of three studies that were published in Science journal on March 15. The study Faith co-authored focused specifically on environmental dynamics during the Middle Stone Age in East Africa, while a second study looked at archaeological evidence of behavioral changes and use of exchange networks. The third study focused on a timeline of the Middle Stone Age transitions.
The three studies were part of a collaboration between 17 institutions, among them the Smithsonian Institution, National Museums of Kenya, Berkeley Geochronology Center, Harvard University, George Washington University, University of Michigan, University of Missouri and University of Bergen.
