They went north, into the teeth of the Ice Age, into direct competition with giant carnivores and stocky Neanderthals who had already adapted to life in the cold. They went north, into a world of challenge, where fruit, vegetables, and game were not available all year long and where efficient weapons, clothing, and housing were necessary. In abandoning Africa, they embraced a wider world that could be survived only through the development of technology. Thus was born Homo technologicus, man the inventor, amid fire and ice. Thus humanity transformed itself from an East African curiosity to the dominant species on this planet.
In a sense, the biblical tale of Genesis tells this story but has it backwards. It was not eating of the Tree of Knowledge that forced humankind to leave Paradise. Rather, it was the abandonment of Paradise that forced humanity to seek the forbidden fruit.
Robert Zubrin
Entering Space: Creating a Spacefaring Civilization