"Early man never committed himself to a single source of food, or a single mode of life: he spread over the whole planet and tested life under radically different circumstances, taking the bad with the good, the harsh with the temperate, glacial cold and tropical heat. His adaptability, his non-specialization, his readiness to come up with more than one answer to the same problem of animal existence-- all this was his salvation." - (Mumford, L (1967). Technics and Human Development.)