Early Native Americans Caused Climate Change

Native Americans may have produced climate change when they killed the American megafauna in the Mesolithic era:

Felisa Smith and colleagues [argue in]: "Methane emissions from extinct megafauna." . . . that the extinction of the mammoths, mastodons, horses, camels, steppe bison and other big herbivores may have helped trigger the Younger Dryas:

"Our calculations suggest that the late Pleistocene extinction resulted in a decreased annual methane flux of ~9.6 teragrams (Tg) (range 2.3 to 25.5 Tg; Supplementary Tables T1 and T2). Interestingly, ice-core records of methane concentration reveal an abrupt drop of >180 ppbv at the onset of the Younger Dryas cold event, about 12,800 years ago (Fig. 1). The drop seems to be synchronous with the extinction of New World megafauna."

Plant and animal domestication in the Fertile Cresent and the associated earliest agricultural societies immediately followed the Younger Dryas. So, the Neolithic Revolution may have been caused in part by the North American megafauna extinction.