UMD Professor is Co-Principal Investigator on the Project
A drastic change in the climate of tropical Africa may have significantly driven early human evolution, an international team of scientists has found.
Professor Thomas C. Johnson, UMD Department of Geological Sciences and Large Lakes Observatory (LLO), was a co-principal investigator with the scientific team.
Professor Johnson and Professor Erik Brown (also from the UMD Department of Geological Sciences and LLO) were co-authors on the African study research paper.
The team's findings were published in the Sept. 4-7 installment of Early Edition, published online in the Proceedings of the National Academy of Sciences. Among the findings: A transition from a long period of time (about 135,000 to 75,000 years ago) that included several extreme droughts to a stable, wetter climate - may have stimulated the expansion and migration of early human populations.
The findings are part of a project called the Lake Malawi Drilling Project, funded by the National Science Foundation (NSF). Lake Malawi is located at the southern end of East Africa's Rift Valley, and is the third largest lake in the Southern Hemisphere.
The findings from the Lake Malawi Drilling Project and other similar lake drilling projects in the tropics "are likely to make major changes in our understanding of the Earth's climate history and its effects on our planet's ecosystems," said Andrew Cohen, a research team member at the University of Arizona. "This study shows what a rich record of climate change is in deep and ancient lakes like Malawi." "The sediment cores from Lake Malawi are the longest continuous record of climate change available from the continental tropics," said Paul Filmer, program director in the National Science Foundation (NSF)'s Division of Earth Sciences. "The link between the signals of East African moisture levels in core samples from the lake and a critical stage in human evolution is an important discovery."
ABOUT THE LAKE MALAWI DRILLING PROJECT:
UMD Professor Tom Johnson said, "A number of us in the African lakes research committee built the justification for the major drilling program for well over a decade, and finally made it happen in early 2005. It is gratifying to see that our efforts are paying off with such spectacular early results."
The researchers studied lake cores from Lake Malawi and found that megadroughts characterized some of tropical Africa's driest periods over the last million years or more.
During the most severe episodes, the lake was below 15 percent of its current level--only 100 meters deep rather than 700 meters. Before about 70,000 years ago, the climate was highly variable, African lakes dried up completely and then refilled, and plant and animal populations grew and died out.
Then around 70,000 years ago, the climate became wetter and stabilized, and African lake levels rose dramatically, the researchers found. Human populations grew rapidly and migrated at that time.
"The population expansion and subsequent spreading of 'Out of Africa' human colonizers may have been aided by the newly stabilized climate," said scientist Christopher Scholz of New York's Syracuse University and lead investigator on the project.
The international team includes researchers from the University of Minnesota Duluth, Syracuse University, the University of Arizona, the University of Rhode Island, the University of Akron, the University of Bergen (Norway), the Malawi Geological Survey Department, the Geological Survey Department of Ghana, the University of Illinois-Chicago, the Scottish Universities Environmental Research Centre and the University of Wisconsin-Eau Claire.
Lake Malawi, more than five million years old and more than 2,300 feet deep, is one of the world's oldest and deepest lakes and is considered by many scientists to be one of the natural wonders of the world.
The research team faced numerous severe operational challenges in retrieving the cores. "Drilling in Lake Malawi presented many of the most difficult aspects of both continental and ocean scientific drilling, including a very remote location lacking infrastructure and very deep, 'blue water' drilling operations," says Scholz. Drilling in the deepest site, which was 600 meters, required the construction of a dynamically positioned drilling vessel. The 26 members of the science and drilling teams lived and worked aboard a 160-foot converted fuel barge for six weeks while recovering the cores. Aboard the drilling barge, the teams lived in converted shipping containers, which were crammed in between the drilling rig and the large thruster engines that were required for stabilizing the vessel.