Updated)
Davis took me out when I was probably 14 or 15 and let me work on a Pleistocene sinkhole deposit with him (Picture to the right - scary!). He had me working in a 6 foot deep hole, where he would lower a bucket to me to fill up. I still remember seeing a tiny rodent jaw in the wall of the hole. Very cool for my first dig! Once I got in school I got to know people like Blaine Schubert who had done some cave paleo in our area. But I regress.....During the Ice Age a million or more years ago, Australia was home to a zoo of extraordinary giant animals, including eight-foot-tall kangaroos, wombats the size of hippos, snakes three feet in diameter, and a horned tortoise as big as a Volkswagen. (For a diorama-like gallery of some of these creatures, see Australia's Vanished Beasts.) But none was quite as bizarre or fearsome as Thylacoleo, 
the meat-eating marsupial lion. Pound for pound, this creature had the most powerful bite of any mammal, living or extinct—in fact, its bite was equal to that of a much bigger African lion today. But even though it was the king of ancient Australian predators, Thylacoleo was eventually toppled from its throne, dying out along with all the rest of the outsized beasts. What happened to drive so many extraordinary megabeasts into oblivion?
In "Bone Diggers," NOVA joins the Australian expedition to retrieve a rare intact skeleton of the meat-eating marsupial. The analysis of its bones throws new light on Thylacoleo's many peculiarities, notably the question of how it attacked its prey (see Anatomy of Thylacoleo). And, finally, the show digs into the mystery of what finally overwhelmed the giant Ice Age creatures and whether early human hunters were responsible.
The adventure begins when paleontologist John Long receives an e-mail from an amateur explorer with a tantalizing photo attached. The photo shows an apparently intact skeleton of Thylacoleo in the depths of a remote cave in the outback. Since no one has found a complete skeleton before, the discovery would be a paleontological milestone. So Long and his colleagues at the Western Australian Museum set out on an arduous expedition, crossing the desolate Nullarbor Plain to pinpoint the remote cave shown in the e-mail. Over the next three weeks, exploring the dangerous recesses of the ancient cavern, the team finds a remarkable trove of fossil remains—including several astonishingly well-preserved Thylacoleo skeletons together with previously unknown species of giant kangaroo.
Back in Perth, the team begins studying the bones and building up a picture of the marsupial lion's unique anatomy and behavior. Although most marsupials such as kangaroos and koalas are herbivores, Thylacoleo was something completely different—a fearsome predator with pincer-like front teeth and a slashing front claw on its thumb. Yet it wasn't built like a lion; with its low-slung body and short legs, it could never have chased its prey at high speed. Instead, it probably waited in ambush for its next meal, perhaps dropping from trees.
In the final scenes of "Bone Diggers," NOVA investigates the mystery of Thylacoleo's disappearance and that of all the other Australian giants. A fierce controversy turns on when exactly this continent-wide extinction occurred. The debate is split between advocates for a late date at the cold climax of the Ice Age some 30,000 years ago, when climate stresses would have been particularly severe. The competing camp claims the extinction was much earlier, around 50,000 years ago, when the climate was milder and the first humans arrived in Australia. While it's unlikely that humans could have directly over-hunted all the huge animals, Aboriginal hunters may well have set fires that gradually changed the profile of vegetation in the outback, making it harder for Thylacoleo's prey to get by. Although it was the king of beasts, Thylacoleo was probably vulnerable to shifts in the food chain. (For more on this mystery, see The Extinction Enigma.)
Whichever theory is correct, the riddle has implications that stretch beyond Australia. Creatures like woolly mammoths, mastodons, cave bears, giant sloths, and many other species all died out on other continents as the Ice Age ended and human populations expanded. The jury is out on just how big a role human predation played both in Australia and on the worldwide stage.
Tomorrow evening (at least here, check your local listings), NOVA debuts a new show all about Microraptor and its ability to use its wings. I am looking forward to this show! Last week they had a great episode about Ape communication (Ape Genius) that just blew me away. If you get a chance, be sure to check out that episode as well.
