Out of Africa - human prehistory and pre - historic African drought

Thomas Johnson, professor at the University of Minnesota Duluth and Syracuse associate professor of geology Christopher Scholz have been studying the climate of Africa for over 20 years. Their studies of palaeolimnology, - studies of lake sediments using plant / algal/ mineral remains are yielding some fascinating insights into human evolution and history.

Recent drillings in Lake Malawi and Tanganyika in East Africa, and from Lake Bosumtwi (Bosomtwi) in Ghana in a team including Andrew Cohen from the U of Arizona, John King and Kate Moran from the U of Rhode Island and Michael Richard Talbot of the U of Bergen in Norway have produced some fascinating results about the pre-hstoric African climate.

Results provide evidence of a prolonged equatorial drought some 75,000 years ago. This resulted in Lake Malawi, now an inland sea some 550km long and 700m deep being reduced to two tiny lakes 10km across and 200m deep. (Guradian article Sept 2003 ) Lake Bosumtwi is located in an old comet crater which is now a 10km-wide lake it lost all of its water. Lake Bosumtwi is unique to science, says Professor Koeberl a geologist from Vienna University, Austria.

"It is the youngest large impact crater we have on Earth, and it's very well preserved. There is no crater of the same size that is younger; and there is no crater that is better exposed or larger." No rivers flow through the very still lake surrounded and shielded from winds by high mountains. As a result, Lake Bosumtwi mud deposits hold an unrivalled record of tropical weather going back through several ice ages.

There are 11 known species of fish in the lake, including one endemic cichlid (Tilapia discolor). Two of the cichlid species are mouth brooders, meaning a parent holds the live-born fish in their mouth to protect them until they reach a certain stage of development.

The timing of this drought coincides neatly with current "Eve hypothesis" of human evolution.

Genetic studies increasingly support the theory that modern human society is descended from a group of around 10,000 individuals who lived in East Africa at the time of this drought crisis.

It is therefore possible that the drought was a causative reason for the exodus from Africa. This was a profound impact on the landscape," said Christopher Scholz, from Syracuse University, US.

Friends of Lake Bosomtwe can be found here http://www.geocities.com/lakebosomtwe/ and is based Department of Physics, Kwame Nkrumah University of Science and Technology (KNUST), Kumasi., where all business transactions including projects planning take place. Efforts are being made to acquire an office close to Lake Bosomtwe in the future.

For Ashantis, this large crater lake (10 km from capital Kumasi) with a diameter of 10.5km is sacred as legend has it that after death, the soul of an Ashanti goes to Lake Bosumtwi to bid farewell to their god Twi before departing for the afterlife.

Norcan a subsidiary of the giant AMI Resources Incorporated, a Vancouver, British Columbia based exploration and development have been granted by Ghana’s Minerals Commission prospecting licenses but the company is yet to obtain an environmental permit by the Environmental Protection Agency.

Pib of Lake Bosumtwi