"Prior research has found that the Great Rift Valley has experienced great changes over the past couple of million years. Because of its unique geography, the area has been particularly sensitive to changes in temperature and rainfall amounts. During periods of abundant rainfall, huge lakes formed along with lush vegetation—times of less rain saw lakes dry up and deserts creep in making life difficult for those that lived in the area. Shultz and Maslin suggest it was the severe changes in the local environment that tested the brains of the creatures that would eventually evolve to become modern man, causing an increase in size and complexity.
Read more at: http://phys.org/news/2013-10-local-east-african-climate-variability.html#jCp
But don't bother. The increase in size and complexity follows periods in human evolution of intense fossil fuel burning.
The FatherLand has Wised Up and is Going To Burn Hard Coal Again into the Forseeable Future. SaaaaaWeeeeeeeeeeeet.
Dats Wat I Call Human Evolution.
Green Subsidies and Green Energy is Bankrupting Da Peoples and Country.
So Sweet Fossil Comes to Da Rescue.
Thanks Extinct Dead Animals/Plants,Super Long Gone Dead Animals and Plants fO yO Gifts of Lower Costs fO Heat, Cool, Light and All Kinds of Goodies.
However, I Do Agree with China building 400 New Nuke Plants over next 10 years, because Dey Be Doin' 'it' Right. Much Less Costly and Higher Safety by Their Methods. Why can't rest 'O World dO 'it' Like Them?