"All civilizations can be understood to a limited extent purely in thermodynamic terms.  From the food that keeps our bodies at proper metabolic temperature to the draft animals, engines, or nuclear reactors that propel our vehicles, the connection between energy and culture is close and causal."—Thank you, Robert J. Wenke & Deborah I. Olszewski for Patterns in Prehistory, Oxford University Press, 2007, p.484