The rise in human population continues to exert enormous strain on earth’s ecosystems and finite resources. Scientific American recently devoted an issue to one solution among many needed to solve this worrisome situation. The cover reads, “We have seen a brighter future, and it is urban.” People living in dense urban environments “typically have smaller energy footprints, require less infrastructure and consume less of the world’s resources per capita.” But, what is the cost? There are always tradeoffs. Alla Katsnelson, from Scientific American, notes that city dwellers suffer “higher rates of mental illnesses, including anxiety disorders and schizophrenia” than their rural counterparts. All the factors underlying this difference are not known or well understood, but some of the possible causes appear to stem from the fact that urban environments are nothing like the ancestral environments from which our sensory systems evolved. As our hunter-gather ancestors learned during the Agriculture Revolution, our biology does not take kindly to rapid upheavals in cultural evolution. In a way, their experience somewhat parallels the one we face today. Put simply, the Industrial Revolution and the subsequent urbanization has been to our sensory systems what the agriculture revolution was to our digestive system.
Around 10,000 years ago groups of hunter-gathers began primitive farming. This shift almost single-handedly changed the course of human history, but our digestive system did not make it easy. Farming “produces 10 to 100 times more calories per acre than foraging.” In lieu of this fact, “from 10,000 BC to AD 1, the world population increased approximately a hundredfold.” Of course, similar to today, the quantity of food rarely related to its quality. Early farmers began eating foods foreign, in type and/or amount, to their hunter-gather ancestors. The first farmers ate less fresh meat and more plants but with less variety. “The carbohydrate fraction of their diet almost tripled, while the amount of protein tanked. Protein quality decreased as well, since plant foods contained an undesirable mix of amino acids, the chemical building blocks of which proteins are made.” The limited set of harvested plants and scarcity of fresh meat caused vitamin shortages rarely experienced by hunter-gathers. These shortages contributed to diseases such as beri-beri, pellagra, rickets, and scurvy. The average height of humans who adopted farming dropped by almost five inches, and the poor diet can partly explain the increase in infant mortality among early farmers.
Obviously, farming did impart many advantages. If not we would still be hunter-gathers. The sheer quantity of people, regardless of health, created a qualitative advantage all its own. Jared Diamond writes, “a larger area or population means more potential inventors, more competing societies, more innovations available to adopt—and more pressure to adopt and retain innovations, because societies failing to do will be eliminated by competing societies.”
