Samples of ancient sediments from a lake basin in East Africa have revealed that arid conditions developed in the area around half a million years ago, an environmental change that could have played a major role in human evolution and influenced advances in stone technology, according to an international research team that includes geologists from Georgia State University.
The team of geologists and anthropologists drilled deep cores in Lake Magadi in Kenya to obtain ancient sediment samples that date back a million years ago to the present. Georgia State researchers conducted mineral analysis on thousands of samples, and their collaborators performed other types of analyses.
Lake Magadi is one of five sites across the East African Rift that is being studied as part of the Hominin Sites and Paleolakes Drilling Project. Two additional sites are also being studied in collaboration with the Smithsonian Institution and Indiana University.
The findings, published in the Proceedings of the National Academy of Sciences, provide clues into how environmental and climate change may have played a role in human evolution and how early humans developed early stone technologies.
"The sediments that accumulated over the last million years show us that Lake Magadi used to be fresh water and gradually over the last million years has gotten more and more saline. That tells us that arid conditions developed in East Africa about half a million years ago," said Dr. Daniel Deocampo, collaborating author of the study and professor of geosciences at Georgia State. "On top of that long-term increase in aridity in East Africa, there were also higher frequency environmental changes. There were shorter-term fluctuations where you might have some wet centuries and some dry centuries.
"The reason why this is important is that when you see these fluctuations really kicking in, that's right about the time when the Middle Stone Age technologies were being developed by early human ancestors, about a half million years ago. These are really more meticulously made artifacts, not the crude, stone tools of a million years ago."
While the researchers can't directly link climate change to human evolution and advanced technology with evidence at this point, they're using geological data to understand the details of how the environment changed.
"I think everyone in the community agrees that environmental change plays a role in evolution, including human evolution and the development of technology," Deocampo said. "The problem that we're trying to address is the details. In some ways, this is kind of the first step because by drilling these sediments we can better understand how the environment changed, and that's the first step to understanding how that environmental change affected human evolution. Those are questions that will be addressed by evolutionary biologists and anthropologists. As geologists, we're providing data on how the environment itself changed."
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