Ancient Humans Thought Experiment (2)

Humans arose during the last two million years, according to available fossil evidence, with so-called “modern humans” – that is, humans leaving behind evidence of culture, art, technology – emerging perhaps as recently as 70,000 years ago, or perhaps 200,000 years ago. Nobody is quite sure and a bitter argument is raging about the exact when and where, though nearly everyone agrees the first such “modern” people arose somewhere in Africa before migrating elsewhere. This means that humans evolved coincident with the ice ages, that two million year period we call the Pleistocene within which ice has advanced and retreated on a roughly 100,000 year cycle, at least 20 times, with the most recent ice age having its “maximum” about 20,000 years ago before retreating until, maybe 12,000 years ago, the ice was mostly gone (except for some remaining caps in Canada and Eurasia). But, before that 20,000 year ago maximum, there were many rises and falls during the previous 80,000 years. It seems that even during the height of an ice age the summers could be hot, maybe as hot as today, just shorter, and of course the winters were colder. It also seems that the temperature could rise and fall over a very very short period, maybe as little as a year or two, certainly a decade. It seems likely that the way an ice age begins is not that somehow glaciers far in the north grow thicker and thicker and then march inexorably south to cover much Continue Reading →