This is CBS, Eye on the World. I'm John Batchel with Professor Dan Flores. The book is Wild New World, the epic story of animals and people in America.

The large predators, the large mammals, mastodons, dire wolves, saber-toothed tigers, removed, opens up what Dan introduces me to call niches, and those niches have

replacements. This is a profound turn for the hunter-gathering group societies that spread across

North America. Dan, the filling of these niches, that's part of a story that's ongoing through all of

these epochs that we're talking about, that there's a balance, and when that balance is

disturbed, nature seeks stability again. Is that the way to read this, Professor?

Well, that is certainly a way to read it.

I would say that whenever a niche opens where there is, for example, the possibility of grazing on

immense grasslands that once had been home to mammoths and other grazing creatures.

What tends to happen in response and what happened in North America 10,000 years ago is that

an animal that is left, like the bison is going to expand into that niche that's been abandoned by other creatures.

And this is when we see the huge population explosion of the American bison into the millions

that we think of in our last four or five hundred years of history.

And it's a smaller animal than the bison that had preceded it in the Pleistocene and are now extinct.

In fact, it's an animal that probably is shaped by the presence of human hunting and predation.

So it has anthropogenic origins even in its natural history.

And in that 10,000 year period after the Pleistocene is over, from 10,000 years ago down to the time when old worlders began arriving in America, is this kind of marvelous

period of a vastly long time when native people, most of them in the beginning of this

10,000 years, hunter-gatherers, although agriculture does emerge in the last 2,000 years or so of that 10,000,

who spread across North America and develop a set of ecological adaptations and economies

that allow them to actually preserve the diversity, the wonderful richness

of the remaining animals that had survived the Pleistocene in North America.

...