Some people go to Africa to sightsee or go on a safari. A UW-Eau Claire associate biology professor went there to see why people left it thousands of years ago.

Through an African trip and analysis of sediment samples, Kristina Beuning, in conjunction with an international team of scientists, conducted research on Lake Malawi in eastern Africa that could explain why humans originally moved out of the African continent. Sarah Ivory, a 2006 graduate, also worked on the research. Their findings will appear in the Oct. 16 edition of Proceedings of the National Academy of Sciences.

Beuning said plant fossils, insect fossils and algae shell remains in sediment cores from the lake bed revealed massive droughts in the region from about 133,000 to 88,000 B.C. Beuning said it could reveal the era and reason that humans migrated to other parts of the world.

“The most important implication of this work,” Beuning said, “is the ability to date the time of the likely movement of early humans out of Africa. We have not been able to date that before because there really wasn’t enough evidence to explain why. Not only can we potentially date it, but we have a reason for it now.”

To capture the samples, researchers and a technical crew traveled on a specialized boat to the middle of Lake Malawi, though Beuning was not on it. Her last trip to the lake was in 2002 and the core sampling was in 2006. To get the cores, the crew would send down a pipe into the sediment, followed by a drill to capture the material.

When the researchers analyzed the sediment, they realized there were three extreme droughts 135,000 years ago to 90,000 years ago.

Beuning said there are traces of human occupation in tropical Africa before this time, but they disappear at that point. As the drought subsided in tropical Africa between 88,000 and 68,000 B.C., a brief window existed when climate in the entire eastern Africa region would have been conducive to settlement and migration. By 68,000 B.C., the potential passage out of Africa would have blocked due to extreme drought in the North.

Beuning added oceanic expeditions and research on a lake in western Africa support their findings, as do settlements throughout the world.

“The timing of this fits really well with understanding the movement once they got out of Africa,” Beuning said. “It makes a lot of sense with regard to the pieces of the puzzle that we have in different parts of the world.”

For Ivory, the work was quite extensive. Like Beuning, she focused on plant fossils and identified pollen grains with a microscope. As the only undergraduate student researcher for the paper, Ivory said she felt nervous in the beginning.

“I really didn’t know that it would get to this level when I started the project,” Ivory wrote in an e-mail from France. “Being the only student researcher on the team was incredibly overwhelming, especially at first. I was really lucky, though, since I got introduced to a really nice group of scientists.”

Ivory said she found the work to be very rewarding.

Beuning did too, and she said she was able to appreciate the African culture and people. She visited Africa 10 to 15 times and plans to go back. Beuning said that on this particular trip, the results were substantial and they will provide a great benefit to the general public.

“It’s rewarding to work this hard,” Beuning said, “and more importantly, to have a broader community recognize the importance and broader significance of the work that you’re doing.”