Demise of the dinosaurs

I heard a talk by Frank Wind (pronounced as in “gust of” rather than “wind up”), a retired geologist, on the dinosaur extinction.

Frank started by saying Darwin is his patron saint. He also cited a book by journalist Elizabeth Kolbert, The Sixth Extinction (concerning the one currently underway), and a New Yorker article by Douglas Preston, The Day the Dinosaurs Died. That was actually the fifth and (until now) last mass extinction of species on this planet, 66 million years ago (MYA); the first occurred about 440 MYA. The most severe was the Permian Extinction, about 250 MYA, killing over 95% of marine species and 70% of terrestrial ones.

Those early creatures must have really pissed off God. Except, of course, that he created the whole shebang a mere 0.006 MYA. To be exact, in 4004 BCE. On October 2. At 6 PM. That was the calculation of Bishop Ussher, by parsing the Bible’s chronology, in 1650. Which Biblical literalists today still take as gospel. They place Noah’s flood at 2348 BCE, which did for the dinosaurs. But even that theory is a bit problematical, unless you suppose every dinosaur species literally missed the boat. Indeed, Frank showed a cartoon with the ark departing, two dinos standing ashore, one saying to the other, “Oh, crap! was that today?

And the dinosaurs could not have died out much earlier because, of course, death itself was introduced into the world in consequence of Adam’s “sin.” But actually, the Bible has nothing at all to say about dinos, which were not even discovered until the 19th century.

The whole concept of extinction wasn’t really a thing till then, most people (well, Christians) believing life on Earth unchanging. Discovering dinosaur fossils threw them for a loop. And even science at that time was kind of stumped to explain how such a whole big range of creatures could have more or less abruptly vanished from the scene.

Not until recent decades was a good theory offered, by Luis and Walter Alvarez, father-and-son scientists. They ascribed dino extinction to a huge asteroid smashing into the Earth. There is evidence of such impacts happening periodically, in the form of 190 craters. And the Alvarezes pinpointed remains of the gigantic 66-MYA Chicxulub crater in the Yucatan peninsula and coast. They also found much evidence in the geologic record, identifying a distinct boundary between sedimentary layers at just that time, with the in-between layer being notably different, showing a very high iridium content, which could only have come from an extraterrestrial source. Such evidence is found as far away as New Zealand (can’t get much farther), proving how dramatically the planet’s environment was affected. Frank also pointed to  some fossils discovered in the U.S., showing directly how animal life suffered.

His talk included some vivid descriptions of just how catastrophic an asteroid hit that big would have been. Unfortunately I missed that part because the talk was on zoom and my internet connection cut out. But you can fill it in from various disaster movies you’ve seen.

Not all scientists buy this asteroid theory. They don’t deny the impact, but don’t think it alone can account for the extent of the extinction. Pointing instead to a spate of big volcanic eruptions that seem to have occurred shortly before. But they accept that the asteroid didn’t help.

We may miss having dinosaurs around (though we do have birds, which are their descendants). However, Frank pointed out, it was the demise of the dinos that cleared the way for the flourishing of mammals, which in turn led to the evolution of you-know-who. Though some misanthropic cynics would say this was not such a blessing.

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