Wednesday, January 31, 2007

Aussie Bones

From my limited perspective, real paleontology amounts to far more digging and head scratching than a rational person enjoys. It appears to help if you also know how to argue, cuss, and speak Latin. ~Robert Kirby

One rarely hears about fossils being found in Australia. Even the Sahara, long regarded as a poor source of finds, has become better known as a source for dinosaur and primate remains. And, of course, the Badlands of the United States and the Chinese deserts have been long known for their museum-filling capability. It's not that there aren't fossils down under, but they appear to be harder to find. One particularly good fossil bed, for example, is in tidal water, requiring a lot of slogging and draining to extract the bones. I imagine that another reason may be that the continent may have lacked some of those convenient conditions (inland seas, flash floods) that cover bones and render them available to diggers eons later.

Of course, if they're going to take five years to report a find, that's not going to raise their profile, either.

I'm being facetious. Finding a bunch of fossils and making sense of them are two very different things. So, despite the fact that a huge find of bones was found in limestone caves under the Nullarbor Plain was found in 2002, proper paleontology requires that people begin to figure out what's there before rushing out to shout about it. Very well, then, what's there?

What is there is a veritable "What's What" in Australia's prehistoric past. How about 23 extinct varieties of kangaroo? Or a marsupial lion? So far, 69 vertebrate species have been found, including mammals, reptiles, and birds. They got there because the Thylacoleo Caves (as they are now known) are natural traps. Tubes lead up to the Nullarbor Plain, and these are camouflaged by bushes or other growth. An animal comes along and pokes its nose into the brush looking for a morsel and ends up tumbling into the cave below from where there is no escape.

Sad for the ancient 10-foot-tall kangaroo but perfectly wonderful for the modern paleontologist.

The creatures date from anywhere from 400,000 to 800,000 years ago. All are now extinct, although some were around up to 11,500 years ago. Whenever such a large number of specimens turns up, it gives scientists a chance to speculate on extinction mechanisms. Climate change has long been a suspect in the demise of large Australian fauna, but the caves seem to indicate that the Nullarbor Plain has been arid throughout the 400,000 to 800,000 years that these animals wandered there. So, we look at the ever-popular culprit: Man.

Another article raises the specter of over-hunting, primarily because, since scientists didn't dream that there were so many species supported on the Plain, then it must have been people that wiped them out. That's a bit of a leap of logic. The flora changed considerably over the time period; it hasn't been determined that all of these species were existing at the same time; and, (and this is a big one to me), there's no evidence anywhere of hunting activity by humans.

As one of the scientists puts it, just because a species was arid-adapted 200,000 years ago, there's not enough information to extrapolate that to 40,000 years ago and announce that "Yep, them ornery humans did it." In fact, in places where bones of both megafauna and humans have been found, like Cuddie Springs, there's no evidence that the animals were hunted.

None of this is to say that humans didn't play some role in the demise of some of the large animals, perhaps through burning off brush or through some level of hunting. But, not enough information is available yet to draw those sorts of conclusions. A site like this has a lot to tell us, and it's just beginning to reveal its secrets. After all, it took around half a million years to accumulate all this information. It is not unreasonable to think it might take more than five years to figure it out.

I suspect the Nullarbor Plain will be throwing more curves at the scientists over the next few years.

No comments: