Q:   How is it known what kind of skin the megatherium had? On Walking with Prehistoric Beasts, it was stated that the megatherium had a "chain-mail like" hide. How did you and your colleagues find out about this?
— Stan
A:   I wasn't involved with that part of the show but I do know that some of the giant ground sloths (e.g., Glossotherium) had such "chain-mail like" hide, with little bean-like bones (called dermal ossicles) embedded in the skin. These animals became extinct only recently and there is plenty of fossil material, including patches of preserved skin with hair and ossicles still in place.

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Q:   Is it true that some animals evolved, then died out, then evolved again? If so, was the sabertooth such an animal?
— Richy B.
A:   It is true that certain kinds of animals have evolved several times, and the sabertooth is one of the best examples of this. Saber-toothed predators have evolved many times in the mammal lineage, not only among cats but also among other groups, including one marsupial species from South America. Within the cat family, saber-toothed forms also evolved repeatedly. Our time is quite unusual in that no saber-toothed predators are around now.

Just to make sure that there is no misunderstanding I should also say that it is not true that individual species go extinct and then evolve again. For a species extinction is forever, but evolution also creates new species all the time. Just now species go extinct much faster than new ones appear, but that is not the normal state of the world.

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