The anthropologist named Jared Diamond has gotten loads of press over the past few years for a couple of great books he's written, "Guns, Germs and Steel" and "Collapse." It was an essay he wrote back in the 1980s that really got to me, though. Called "The worst mistake in the history of the human race," Diamond comes up with the radical but thoroughly plausible hypothesis that the introduction of agriculture was the worst choice humankind ever made.
After the advent of agriculture, humans became sedentary. Our lives centered around our cropland, and with an abundance of food, a lot of people could live in one place. Cities arose, and so too did all manner of problems we humans didn't have before we started raising crops and livestock.
Living in close quarters allowed epidemic disease to spread. Crop failures led to famine. Crop surpluses led to the rise of currency and, most notably, levels of power, since a person with a surplus of food had a natural advantage over a starving neighbor. Agriculture also led to war. With new value placed on land, money, crop surpluses and subjugated people, groups now had reason to compete with one another and this competition often turned violent.
I came across a natural experiment that supports Diamond's hypothesis in a Scientific American article. The Enga people of Papua New Guinea lived relatively peacefully until 18th century European explorers introduced an unlikely trigger for social unrest, the sweet potato. The crop grew well in Oceania and the Enga went crazy for it. More people were drawn to farming centers and about 200 years ago the group experienced an outburst of war.
Don't be dismayed, though. The same article pointed out that humans have actually gotten less violent as we've adjusted to living in society over the millennia. Apparently sweet potatoes and kingdoms were just growing pains of us humans learning to sacrifice our personal interests for the greater good of society.
Why, here's Jared Diamond now: