This is CBS, I in the World. I'm John Bachelor 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 Den introduces me to call niches, and those niches have replacements.

This is a profound turn for the hunter-gathering groups, societies that spread across North America.

Then, 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 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 proceeded it in the pliesicane 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

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