We've known now for a long time that humanity's earliest roots could be traced back to Africa. Indeed, it is thought that around 70,000 years ago early human populations first began to expand and leave the African continent to spread out across the world. Up until now, scientists had believed that these migrations and population fluxes were driven by the rise and collapse of high-latitude ice sheets. An international team of scientists has put forth a new hypothesis — suggesting that a wetter climate prompted by a dramatic rise in African lake levels may have propelled early human evolution.
In a recently published study, the researchers hypothesize that a transition from a long period of droughts to a wetter, more stable climate could have helped early human populations grow and migrate to other continents. "Previously it was thought that the migrations and population changes of early modern humans were driven by the growth and collapse of high-latitude ice sheets. Our research suggests that instead, prior to 70,000 years ago, wet-dry cycles in Africa were driven by shifts in the Earth's orbit around the sun," said Christopher A. Scholz, a professor of earth sciences at Syracuse University and the study's lead author.They analyzed cores they obtained from drilling in Lake Malawi, located at the southern end of Africa's Rift Valley, and discovered that so-called "megadroughts" caused lake levels to vary dramatically — sometimes drying the lakes up completely — resulting in the fall and rise of plant and animal populations. Once the climate stabilized about 70,000 years ago, the lake levels rose and remained at their higher values, facilitating the large-scale move and growth of early human settlements.
"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. This study shows what a rich record of surprises in climate change can be learned from deep and ancient lakes like Malawi," said Andrew S. Cohen, a professor of geosciences at the University of Arizona.
That and it also demonstrates that climate change has, in fact, had some major upsides over the course of mankind's history. Just not right now.
See also: ::Evolution, Accelerated, ::The Shift Movie: The Next Stage in Human Evolution?
Image courtesy of i_pinz via flickr