Yet for most humans in the northern hemisphere, moving up the Great Chain of Energy was an unalloyed good. People could follow plants and other animals north into regions that were previously too cold to support them, and by 13,000 BCE (the exact date is disputed) humans had fanned out across America, where no ape-man had trod before. By 11,500 BCE people reached the continent’s southern tip, scaled its mountains, and pushed into its rain forests. Mankind had inherited the earth.
