Out of the Kenyan Mud, an Ancient Climate Record

摘要

When Richard Potts, Anna Behrensmeyer, Alan Deino, and Richard Bernhart Owen get together, it's usually at camp at Olorgesailie in Kenya's Great Rift Valley. The paleoscientists labor for hours in the hot sun, chipping away at exposed rock outcrops to develop a timeline for artifacts and other relics of the human ancestors who once lived nearby. But on a cold spring day earlier this year, they gathered with a dozen other researchers in a small lab at the University of Minnesota to analyze something quite different: 190 meters of mud, sand, and gravel cored last year, from what they hoped was once a lakebed 20 kilometers from their outcrops. The team had never tried to drill a core before and hadn't even known for sure that a lake ever covered the area. But as the researchers kicked off their "core sampling party," they hoped that the mud would resolve into thousands of distinctive layers, each representing a different climate regime, ultimately reaching back 500,000 years. The goal: to test ideas about the role of climate variability in human evolution, by getting a continuous record of climate indicators from a place where hominins lived and died (see story p. 474). The project "has high potential to reconstruct the long-term history of environmental change," says team member Vanessa Gelorini, a paleoecologist at Ghent University in Belgium.