About 15000 years ago the Pleistocene ended beckoning warmth and stability. These conditions allowed homo sapiens to develop agriculture which in turn allowed them to break out of balance with nature and proliferate like a cancer. This drastic overpopulation is now causing global warming, and wrecking the fragile ecosystems that sustain the conditions for the survival of our (and almost every other) species. It's beautifully logical, and obvious, in retrospect. And I'm only writing this because there's a moral, a principle, in there somewhere if you care to dig it up.