Friday, May 22, 2009

Still Looking for the Smoking Gun

The dinosaurs became extinct because they didn't have a space program. ~ Larry Niven

When last we met -- well, I was here, where were you? -- I was discussing a new theory that pterosaurs, at least the big ones, may not have been able to fly. Now, that is the sort of discussion that can get a group of paleontologists reasonably worked up, but if you really want to see a bunch upset scientists, start talking about the last great extinction event, when the dinosaurs ceased to walk the earth, 65 million years ago.

Ever since dinosaurs were discovered, people have been wondering where they went. For years, the prevailing theories were some sort of disease or significant climate change. Then, in 1980, a geologist named Walter Alvarez got to wondering about this thin black stratum he kept finding at the end of the Cretaceous. When he and his father, physicist Luis Alvarez analyzed the material in the stratum they discovered an abnormally high amount of the element iridium. The most likely source for a lot of iridium was from a meteor impact. Since the iridium layer (known as the K-T boundary, from the German form of Cretaceious-Tertiary) was found all over the planet, it had to be a big impact. They theorized that this could have been what did the dinosaurs in.

Now any group of scientists don't really like outsiders telling them their business, and paleontologists are no different than anyone else in this regard, so the Alvarez' theory was met with polite skepticism at best and outright derision at worst. Then someone found a big hole in the ground.

Actually, the big hole was mostly under water, off the coast of the Yucatan peninsula. It was dubbed Chixulub and seemed to settle the issue once and for all, at least for most people. It was generally now assumed that most, if not all, dinosaurs were wiped out by the catastrophic event.

Well, maybe not. Some scientists got to wondering if the dinosaurs weren't already on the decline because of climatic changes or maybe because of the eruption of the Deccan Traps, volcanic activity on a massive scale. And then there was Gerta Keller, who didn't think Chixulub had anything to do with it at all. First she announced that another meteor was responsible for the extinction, which is a pretty fine point. If two meteors hit the Earth close enough in time to have resulted in one K-T layer, asking which one killed the dinosaurs is like asking whether the fall or the sudden stop is what killed a guy falling off a cliff.

Then a little while later, Ms. Keller came back and said it wasn't meteors at all. It was the Deccan Traps in India that did the deed.

Then, recently, there was an article that was titled, "New Blow against Dinosaur-killing Asteroid, Geologists Say." It turns out that the "geologists" are actually a team led by -- wait for it -- Gerta Keller, who is basically rehashing her theories of three years ago. She announces unequivocally that not a single species went extinct because of the Chixulub impact. She doesn't mention if any went extinct by the other impact she once hypothesized.

One of the problems here is the popular picture that, when the dinosaurs went extinct, they did so in one afternoon, geologically speaking. Meteor hits, worldwide catastrophe, no more velociraptors. The thing is that it is becoming generally accepted that while the a Chixulub-size meteor would not be pleasant, it would not have created the planet-wide fires and other global disasters originally predicated. That said, it would have altered the climate significantly for a lengthy period, possibly long enough to starve a lot of sauropods because of a lack of plant life (thanks to global cooling) whcih would deprive a lot of theropds of their sustenance. Add the Deccan Traps outburst, and you have a very difficult time for dinosaurs.

So it's unlikely that any one cause killed the dinosaurs off, but it's patently silly to deny the effects of the Chixulub impact. It can't be pinpointed whether it occcured before, after, or during the Deccan eruption, but it would have been a serious blow. Whether it was a killing blow or just one more body shot is the question.

Then there's the whole issue about how long it actually took the dinosaurs to vanish. Generally, as I said, the thinking is that they were in decline and some catastrophe (take your pick) finished them off. But a new theory holds that some of them hung around for about 500,000 years. Of course, the theory is controversial, and not many people are buying into. In fact, unless the Deccan Traps can fit into this new time line, not even Gerta Keller is going to be buying in.

Personally, I don't find it hard to imagine isolated pockets of dinosaurs hanging on for some slightly extended period. I doubt any of the large beasts that normally come to mind when someone says dinosaurs are among those that survived (the story doesn't say what sort of bones were found). But it is easy to imagine smaller saurians, of which there were many, eking out an existence for a little while longer.

Of course, one thing that will come of this most recent theory is that there still could be dinosaurs roaming around, an old sci-fi standby. Worse, some news reader or writer is going to misunderstand the time frames involved and boldly announce that this proves that dinosaurs and humans actually were alive at the same time.

The Fred Flintstone syndrome lives on.


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