How so?
PS: Agree, another Yellowstone eruption would make a 150 ft tidal wave on the east coast look welcome by comparison. I wonder how many Yellowstone tourists realize that they are camping in one of the largest volcanic craters on Earth!
It was contained in Professor Stephen Oppenheimer's excellent book, Out Of Eden. There was an explosion of human branches just after Toba and another lesser one after The Last Glacial Maximum(LGM).
BTW, he also explains why American Indians and some Europeans are the only ones who carry the "X" gene, Toba killed everyone in between and broke the link.
I've read two of his books and highly recommend both, Eden In The East and Out Of Eden.
"Professor Stephen Oppenheimer
Stephen Oppenheimer is a world-recognised expert in the synthesis of DNA studies with archaeological and other evidence to track ancient migrations. He is a member of Green College, Oxford University."