Setting up timeline 3d to 6000 years5/9/2023 ![]() ![]() Not only was this discovery unexpected, but the process of tracking down the animal bones to take samples was more than Somerville anticipated. "If we can find strong evidence that humans did in fact make and use these tools, that's another way we can move forward." "Determining whether the stone artifacts were products of human manufacture or if they were just naturally chipped stones would be one way to get to the bottom of this," Somerville said. He says the possible stone tools from the early levels of the cave may also yield clues. To answer that question, Somerville and Matthew Hill, ISU associate professor of anthropology, plan to take a closer look at the bone samples for evidence of cut marks that indicate the bones were butchered by a stone tool or human, or thermal alternations that suggest the bones were boiled or roasted over fire. Most importantly, is there a human link to the bottom layer of the cave where the bones were found? Previous studies relied on charcoal and plant samples, but he says the bones were a better material for dating. Somerville says the findings provide researchers with a better understanding of the chronology of the region. ![]() "We were surprised to find these really old dates at the bottom of the cave, and it means that we need to take a closer look at the artifacts recovered from those levels." We were just trying to situate our agricultural study with a firmer timeline," Somerville said. "We weren't trying to weigh in on this debate or even find really old samples. The findings add to the debate over a long-standing theory that the first humans crossed the Bering Land Bridge into the Americas 13,000 years ago. Somerville says even though previous studies had not dated items from the bottom of the cave, he was not expecting such old ages. The results are published in the academic journal Latin American Antiquity. The date ranges for the bone samples from the base of the cave ranged from 33,448 to 28,279 years old. The dates for the bones suddenly took Somerville and his colleagues in a different direction with their work. As part of that work, they wanted to establish a date for the earliest human occupation of the Coxcatlan Cave in the valley, so they obtained radiocarbon dates for several rabbit and deer bones that were collected from the cave in the 1960s as part of the Tehuacan Archaeological-Botanical Project. Andrew Somerville, an assistant professor of anthropology in world languages and cultures, says he and his colleagues made the discovery while studying the origins of agriculture in the Tehuacan Valley in Mexico.
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