This is CBS Eye on the World.

I'm John Bachelorette with Jessica Pearson Mark Backoff, where discussing their new book,

A Dog's World, imagining the lives of dogs in a world without humans, Mark immediately

physical shape will change.

One thing that comes to me right away is that the snout, I never recognized that as this

significant feature of the Canis Loop as familiars.

What is the advantage of a longer snout?

Why is it that the shortest snout dogs will likely either change or leave us?

Well, the shortest snout dogs may not be able to breathe very well on their own.

When they're taking a lot of exercise, you know, one of the things that all dogs are going

to have to do is get physically fit, if you will, they're going to have to be able to

get food and defend food, find a home range and a territory and defend it.

And if they can't breathe well, then they'll just lose out.

I mean, there's just no other way to put it when they're on their own.

Their sight may change too, because the longer those dogs may have better sight.

People have speculated that the length of the nose might be important in activities

such as hunting or finding their way around.

I'm not sure we really know that, but the physical attributes of the dogs, you know, body

shape, leg length are going to really change on their own as they begin to breed on their

own.

You know, we don't, we won't be around to force them to breed with certain other individuals.

And so we can expect that they'll be rewarded for speed because they have to chase predators

...