And when he had opened the fourth seal, I heard the voice of the fourth beast say, Come and see. And I looked, and behold a pale horse: and his name that sat on him was Death, and Hell followed with him. And power was given unto them over the fourth part of the earth, to kill with sword, and with hunger, and with death, and with the beasts of the earth.
Tomorrow, Paradox Interactive shall release a new expansion to Crusader Kings II, a magnificent grand-strategy game. The expansion is called The Reaper’s Due and it focuses on the effects of pestilence, especially the Black Death, in the Medieval world. The very theme brings to mind the effects that pestilence has had on the human species since the dawn of civilization.
Among students of human evolution, one of the questions that comes to mind when one is first thinking about that great epic of natural history is whether human evolution has stopped. Although evolutionary biologists will be quick to chime in that evolution never really stops, the question is still one that piques curiosity. After all, has civilization not prevented the culling of the human population that would be necessary for evolution to occur? However, as The Reaper’s Due makes all too apparent, such culling has actually occurred over the course of civilization, and one of the principal reasons has been pestilence.
The human species is now living in a geological era all its own. Yes, Homo sapiens may have attained anatomical modernity in the Middle Paleolithic, or thereabouts, but the species today lives in the Anthropocene. Both the rapid destruction of ecosystems, which happened even during the era of hunter-gatherers, and global warming warrant the creation of a new geological era. However, those two are not the aspects of the Anthropocene that I wish to focus on, that aspect is civilization, the complex network of social interaction by which man has accomplished the challenge of Genesis 1:28 to subdue and have dominion over the earth.
Civilization and the problems associated with living in close coordination with other people, introduce evolutionary pressures that have changed the human species over the past twelve thousand years. It has done so principally because civilization radically changes the ecosystems in which the human species evolves. That change in ecosystem has introduced new challenges in the struggle for existence our species has faced that has affected the human genome. We only need look as far as what happened to much of the indigenous population in America upon European contact to know that some populations have a resistance to some infectious diseases and that resistance probably has a genetic
One of the deadliest among those evolutionary pressures in the threat of disease. The existence of even thousands of human beings living right next to each other changes the very biotic system they are living in. That people tend to often lived on top of their own refuse in densely populated areas creates an ever more hospitable ecosystem for the flourishing of bacteria. Even worse, malnutrition is prevalent in civilizations across the world because of the difficulties that agricultural societies have in supplying all of the necessary nutrients. As a result of malnutrition, people are less likely to be able to fend off the pathogens afflicting them, to the benefit of the population of those pathogens.
Overall, civilization changes the ecosystem that human beings find themselves in. Although most of those changes may be said to be for the better, the threat of disease is certainly magnified. As a result, human beings have to struggle against disease to a much greater degree than they did. That struggle for existence has exerted an evolutionary pressure on the human population. Pestilence has been one of the pressures driving human evolution. Moreover, it is an evolutionary pressure generated by human civilization itself.