This is John Batchel.

A wonderful conversation with Daniel Kloat.

It's Kuala time of year down under.

It is summertime, and the koalas are playful.

The little joys have been born.

The moms carry joys around for years.

The koalas live in eucalyptus trees.

They eat eucalyptus leaves, which are really tough,

filled with resin. And here, Danielle Claude introduces us to the evolution of koala teeth.

She describes pinking shears. That's how sharp they are to deal with the eucalyptus leaves. The eucalyptus trees are also

endangered to koalas. Every time I see bushfires now, I worry about the koalas who live in those

bush trees in those eucalyptus trees and the bushfires sweep over them and they don't protect

themselves. They stay with the tree.

Very sad business. In any event, koalas, not bears, they're marsupials, and the joys are very cute.

Koala teeth. What does it tell us about eucalyptus trees and koalas, a deal about that they've evolved together?

Here's Daniel Kloat to explain. Much more of this later tonight.

Yeah, when we talk about koalas or fossils, Australia doesn't have a fabulous fossil record just because of the particular geological conditions we have.

So the fossils we find of koalas are typically their teeth, and the teeth are the hardest part,

they're the hardest bone as it were, so they're the things that survive.

Fortunately, teeth do tell us quite a lot about what an animal eats.

And the complexity of the teeth,

especially for herbivores, tells us how hard the food is that they're eating. So a lot of the

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