Well-known physiological peculiarities of human bodies had much to do with raising our ancestors to the top of the food chain: erect posture, binocular vision, an unusually efficient cooling system, and an omnivorous diet. But these capabilities pale beside the advantages that accrued to proto-humans and then to humans from expanding and more precise modes of communication: first dance, then language. Still later, transportation and communication transcended limits set by human muscles with the invention of wind-propelled flotation and animal caravans, while writing overcame limits of personal memory and face-to-face dissemination of information. Contacts across local social and cultural boundaries tended to propagate best practices, making humankind a uniquely dangerous, constantly changing parasite upon other forms of life.