What exactly does the term 'Sixth Extinction' mean?
We can divide the Sixth Extinction into two discrete phases:
- Phase One began when the first modern humans began to disperse to different parts of the world about 100,000 years ago.
- Phase Two began about 10,000 years ago when humans turned to agriculture.
Everywhere, shortly after modern humans arrived, many (especially, though by no means exclusively, the larger) native species typically became extinct. Humans were like bulls in a China shop:They disrupted ecosystems by overhunting game species, which never experienced contact with humans before.And perhaps they spread microbial disease-causing organisms as well.The fossil record attests to human destruction of ecosystems:Humans arrived in large numbers in North America roughly 12,500 years ago-and sites revealing the butchering of mammoths, mastodons and extinct buffalo are well documented throughout the continent. The demise of the bulk of the La Brea tar pit Pleistocene fauna coincided with our arrival.The Caribbean lost several of its larger species when humans arrived some 8000 years ago.Extinction struck elements of the Australian megafauna much earlier-when humans arrived some 40,000 years ago. Madagascar-something of an anomaly, as humans only arrived there two thousand years ago-also fits the pattern well: the larger species (elephant birds, a species of hippo, plus larger lemurs) rapidly disappeared soon after humans arrived.
Indeed only in places where earlier hominid species had lived (Africa, of course, but also most of Europe and Asia) did the fauna, already adapted to hominid presence, survive the first wave of the Sixth Extinction pretty much intact. The rest of the world’s species, which had never before encountered hominids in their local ecosystems, were as naively unwary as all but the most recently arrived species (such as Vermilion Flycatchers) of the Galapagos Islands remain to this day.