The supercontinent known as Pangaea once hosted less diversity in species on the planet. Viewed as one arena for competition, diversification of species was not only limited, but also not necessary. Pangaea maintained itself as the only continent around 200 million years ago, and began its break up approxmately 180 million years ago.
Hominids arose on the evolutionary chain between 1-3 million years ago. Unlike other animals, hominids benefitted from brains that were geared towards language skills and eventual tool use. These abilities would not be fully recognized unitl the emergence of Homo Sapien, or modern man, about 40,000 years ago. Although Homo Erectus wandered into Europe and Asia 750,000 years ago, the American continents and Australia would remain unknown until Homo Sapien ventured inot them roughly 40,000 years ago. This remained possible due to large ice caps that lowered sea levels and caused straits that were easily crossed. However, with the end of the Ice Age around 10,000 years ago came rising sea levels that would isolate the populations of the Americas and Australia.
The Neolithic Revolution describes that period in time when "humans started to grind and polish rather than chip their stone tools into final form" and "humans invented agriculture, domesticated all the animals of our barnyard and meadow, learned to write, built cities, and created civilization", according to Crosby. However, different locations would experience this revolution at various times. While those in Europe and Asia experienced these changes early on, isolated populations in the Americas and various island groups witnessed these innovations fairly recently or not at all.
