http://www.sciencedaily.com/releases/2011/01/110127141651.htm
1) Climate change occurs even without technology.
2) Assumptions that climate change is bad are unfounded. For all we know the climate change the greens would inhibit may be the change that returns the Arab peninsula to fertile lands suitable for agriculture.
How to explain the Eskimo crossing over from Russia??? Did they come in boats or walk on a land bridge??
Then the controversy about South America on why so much of their buildings were so much like those in Egypt.
Climate and warm winds may in fact allowed for trans Atlantic travel, but the question causes the PHD'S to get into a nose punching argument.
The Pacific we know allowed some fortunate few to travel a few thousand miles, was it the climate that allowed them to do do with westerly winds or by accident??