The modern vast desert belts of Northern Africa and Arabia are very hostile environments and thus a natural barrier for humans and mammals. A successful dispersal was only possible at times when the desert turned into a savannah-type landscape with abundant lakes.
To date, our knowledge of past climate variability in Arabia is very limited due to a distinct lack of suitable climate archives. Fortunately stalagmites collected from various caves on the Arabian Peninsula can now provide detailed and precisely-dated information on Quaternary climate variability back to several million years ago.
Based on previous investigations on stalagmites from Yemen and Oman, we know that stalagmite deposition is only possible during wet periods with rainfall above at least 300 mm per year (present-day average rainfall in the desert is generally less than 100 mm year). However, the current limit of the dating method (Uranium-Thorium dating) is 500,000 years, whereas dispersal of hominids took place between approx. 2-1 million years before present.
For this study, funded by NERC, Dominik Fleitmann and Stuart Black will use a fairly new method (Uranium-Lead dating) for dating very old stalagmites covering this crucial time interval in human history. By dating periods of stalagmite deposition precisely we can identify these periods and establish links between dispersals of hominids and mammals.