March 16 (UPI) -- By studying rocks in Kenya, scientists have uncovered an understanding of human evolution over the last half-million years.
Anna K. Behrensmeyer of the Department of Paleobiology at the National Museum of Natural History and her colleagues over more than 15 years studied the geological history of the East African Rift in southern Kenya. They detailed their findings Thursday in the Geological Society of America Bulletin.
Because the sediments of the newly named Oltulelei Formation in the Olorgesailie Basin were deposited after a 180,000-year period of erosion, they preserved important evidence for human evolution until about 36,000 years ago.
For roughly 700,000 years, the basin was relatively stable. But over the last 500,000 years, it has been divided into sub-basins and experienced rapid change multiple times, from lake to land and back. Early humans and other inhabitants had to adapt to these physical landscapes' changes. This timeframe correlated from the age of Acheulean of "hand-axes" technology to Middle Stone Age technology.
"This only makes sense when we understand the geology of the enclosing rocks, particularly the age of the strata and the nature of the paleoenvironments associated with archeological and fossil sites," Behrensmeyer said in a press release.
She noted that if there are two archeological sites with different types of artifacts in different strata some distance apart, a geological investigation can determine which is older and which is younger.
"This is obviously critical to understanding the evolution of technology," Behrensmeyer said.
Behrensmeyer used traditional section measuring and mapping to document the strata across three different sub-basins. They then analyzed and correlated hundreds of section logs with the help of new computer-based methods. Their research even included a three-dimensional view.
"The stratigraphic record preserved in the Oltulelei Formation advances understanding and poses new questions about how tectonics and climate shaped middle to late Pleistocene faunal turnover and the transition in southern Kenya from Acheulean to Middle Stone Age technology," the researchers wrote in the study.