That earlier post on human migration got me curious about the climate of the ice age. What sort of a world were our ancestors encountering as they spread inexorably around the world? Earth was in a glacial period for most of the time during which the expansion of our species occurred; the current interglacial period we all know and love didn't set in until after humans had colonized every continent (every decent continent, at least - sorry, Antarctica). So what was the world like for those prehistoric peregrinators?
Ask Wikipedia, and ye shall receive:
(You'll have to click on the map or follow the link to be able to read the legend.) This is a standard-issue vegetation map of the sort that always show up in the first section of world atlases, but it shows the world as it was ca. 18,000 years ago. And things were shockingly different. For instance:
-That purple in the eastern US indicates taiga, the coniferous forests which today are found right at the limit of the Arctic tree line in northern Canada. Apparently the Mississippi Delta of 18,000 years ago resembled the Yukon of today.
-Florida was a semi-arid temperate woodland, and the Atlantic coast of the US was boreal forest. Anything north of New York City and Chicago was under ice altogether.
-Much of Europe was under ice as well, and steppe-tundra extended all the way down to the Mediterranean coast. Tundra also had a foothold in the interior of the Iberian Peninsula.
-Interestingly, there were tropical forests and grasslands in many of the same areas as there are today. But the temperate regions really get pinched; it seems that between the subtropical deserts (also in most of the same regions as today) and the ice and tundra of the higher latitudes, there just wasn't much room for the expansive temperate forests which have more recently been characteristic of North America and Eurasia, especially. It seems that the world of 18,000 years ago just had a lot fewer trees.
-Australia? 'Bout the same, maybe a little chillier. The Southern Hemisphere in general, in fact, seems to have been less affected by the last period of glaciation.
Given all this, you can well imagine why humans spread first along the coast of the Indian Ocean, all the way to Australia: pretty much everything north of there was barren, windswept, and cold. It was the North Dakotafication of the world. In fact, as those first bands of humans finally left the amniotic comforts of southern Asia and Africa and soldiered into the frozen lands to the north, an interesting question to ask them would have been: why?