Coincidence of timing The dramatic dry period 6 0 to 5 3 Mya closely coincides with the evolutionary split between forest dwelling Chimpanzees and savanna dwelling proto humans Could there be some kind of closer connection 66 235 26 150 Hutton s observation James Hutton speculating about the origin of salt deposits wrote in his THEORY of the EARTH or an INVESTIGATION of the Laws observable in the Composition Dissolution and Restoration of Land upon the Globe that THE formation of salt at the bottom of the sea without the assistance of subterranean fire is not a thing unsupposable as at first sight it might be Let us but suppose a rock place across the gut of Gibraltar a case nowise unnatural and the bottom of the Mediterranean would be certainly filled with salt because the evaporation from the surface of that sea exceeds the measure of its supply I m not sure that this has any place in the article but it s quite a thought experiment for 1785