The Kansas City Star, 7 December 2004
Milwaukee Journal Sentinel
MILWAUKEE - There are two lines of thinking when it comes to the demise of the dinosaurs. One camp thinks the Earth was bombarded by an asteroid while the giant reptiles' party was
in full swing. Others say the lights were already starting to dim, and it was just a few, late-night guests who were vaporized.
And despite new fossils and data, there appears to be no reconciliation between the camps: They are as polarized as ever.
"It's not like we are a bunch of junior scientists" who are trying to make a name for ourselves, said J. David Archibald, a biologist at San Diego State University who specializes in mammals of the Late Cretaceous epoch. "So, why do we go after each other about this?"
Quite simply, said David Fastovsky, a paleontologist at the University of Rhode Island in Kingston, "people love their dinosaurs."
A paper published recently in the journal Geology appears to show that dinosaurs were "going great guns" when the asteroid hit, said Fastovsky, who wrote the paper with Peter Sheehan - a geologist at the Milwaukee Public Museum - and colleagues from Rhode Island and Johns Hopkins University.
Looking at more than 1,200 skeletal samples representing 560 different kinds of dinosaurs from every continent on Earth, the researchers concluded that not only were dinosaurs doing well at the end of the Cretaceous - 65 million years ago - they were "flourishing," said Mark Wilson, a paleoecologist at the College of Wooster in Ohio who was not involved in the study.
These conclusions fly in the face of a group of paleontologists and geologists who believe dinosaurs had already started to dwindle at least 10 million years before the celestial collision.
So, not surprisingly, the results were not taken lightly.
According to Archibald - who's of the gradual demise group - the authors say nothing about the fact that this crucial period coincided "with the greatest loss of sea in at least 500 million years, and the greatest period of volcanic activity."
"I think the record is too noisy, too many other things going on" to attribute the extinction to just one cause.
The scientists are simply taken with the idea of there being one cataclysmic event because "it's a more exciting story," he said.
And to bolster his case, Archibald re-crunched the authors' database, and came to the opposite conclusion: He found a decrease in the diversity and number of dinosaurs during the last 10 million years of the Cretaceous.
He has submitted his rebuttal to Geology.
So, how is it possible that two groups of researchers could look at the same data, but come up with such polar conclusions?
Archibald contended that Fastovsky and Sheehan used fancy - and unnecessary - statistics to support their "cataclysmic agenda."
"They did it to get the answer they wanted," he said.
But the Geology authors countered, saying Archibald's accusations are nonsense. They used a statistical formula, an algorithm called rarefaction, that was not only typical for this kind of database but also necessary, they said.
"Rarefaction is a common statistical technique," said Wilson, the Wooster paleoecologist. The Fastovsky team used it "quite appropriately."
"It has problems, but you can look for them," Sheehan said. "And our statisticians did not see problems."
In fact, he said, if you just take a gander at the raw data, you'll see the increasing trend.
Steve Wang, a professor of statistics at Swarthmore College who has used the same database - but used a different statistical technique to answer some of the same questions - found similar results.
"This is a nice piece of work," said Wang of the Geology paper. "I thought they did a good job."
Archibald and his group's problem, Sheehan believes, is not really with the statistics, it's with the "paradigm shift."
Before the discovery, in the 1980s, that an asteroid hit the Earth 65 million years ago, the scientific community believed dinosaurs slowly fell victim to a change in climate - the cooling of the planet and shrinking of oceans.
But the Alvarez Hypothesis - the extraterrestrial asteroid impact theory - caused a blow to this long-held gradualist-way of viewing things, said Wilson, the Wooster paleoecologist.
And "now we're told that dinosaurs were doing just fine?" Wilson said. "How can we construct rational historical narratives with the gods occasionally erasing the boards?"
One response, he said, is to "cling to the older ideas." Another: "To look at the evidence carefully and test that conventional wisdom."
But in the end, Archibald said, the only way to experimentally verify what really happened to the dinosaurs is to have our own large-scale asteroid event (sic).
Copyright 2004, The Kansas City Star