USA Today: Chopping down trees with flint axes, planting peas and shearing sheep those all sound like the prosaic duties of the earliest farmers. But those same Stone Age sodbusters were likely changing our planet's climate, researchers are now suggesting, long before the greenhouse gas emissions of the industrial era. And that means the "Anthropocene" era, the time of humans making a mark on the planet more striking than natural forces, extends not just to the beginning of the industrial era but to the...