Comment by adastra22
7 days ago
It'll be settled when the generation of researchers who fought over it retire/die off. The short TL;DR is that the guy who came up with the asteroid theory knew basically nothing about paleontology and paleoclimate, was way outside of his depth (he was a physicist that worked on the Manhattan project). He then made some pretty wild claims given the evidence that was available. When criticized by people who actually knew the field, he would personally attack them and drive public support against them as dinosaurs in a field of dinosaur research.
Then the Chicxulub crater was found and dated to basically the exact same time as the K-T extinction event to within experimental error. So I guess the asshole was right?
Except science doesn't work by smoking guns, as appealing as that would be. There are a lot of contradictory evidence. Better instruments and more careful data collection shows that in some places the fossil record stops prior to the impact layer. Also the fossils are of animals you would expect of an extinction event already ongoing. Oh, and coincidentally right before the Chicxulub impact India hit the continent of Asia and the Deccan Traps started spewing CO2 and other gasses into the atmosphere in volumes that put human-caused climate change to shame. The ocean was acidifying and ecosystems collapsing. Is it really fair to say an asteroid impact killed the dinosaurs, when they were already on the way out?
IMHO the current best theory is the "one-two punch" that the Deccan traps eruptions basically put every large species on extinction watch, then the asteroid impact happened and finished the job. But it has become so political within that research community that people just aren't rational about the evidence, on either side.
The Alvarez hypothesis is notable not just because of its power in explaining the Cretaceous mass extinction, but because of its Copernican-like effect on paleontology.
Up to that point, it was a matter of belief among paleos that bolides were not a significant factor in the history of life. Essentially, that the Earth did not experience frequent or significant impacts after the initial formation of the solar system.
The evidence supporting Alvarez became so compelling that it not only became accepted as the K-T cause, it opened the door to considering bolides for all sorts of previous extinctions--an idea explored by Raup in his book Extinction. It made "sudden catastrophes" acceptable as a serious research subject for the first time since Lyell.
Prior to Alvarez, it was a matter of faith that the K-T boundary must have a solely terrestrial explanation, and the Deccan Traps were elevated to the most likely candidate. But it just shifted the need for explanation--why was there sudden globally catastrophic vulcanism? You say "India hit Asia" but that was not a sudden thing, in fact it's still happening today. Hot spots are still active today. It never really worked, but it was the best they had (or were willing to consider at the time).
You do know that there was an already well studied global mass extinction, the P-T crisis, which is very well studied and clearly the result of volcanism?
I think you are exhibiting exactly the problem with the Alvarez hypothesis that makes people have such a gut reaction to it. It is a Deus Ex Machina that can be invoked at any time to explain a die off even in the face of conclusive evidence to the contrary.
The short TL;DR is that the guy who came up with the asteroid theory knew basically nothing about paleontology and paleoclimate, was way outside of his depth (he was a physicist that worked on the Manhattan project).
Eh, that's underselling Luis Alvarez a bit. He wasn't just "a physicist," he was a Nobel laureate and arguably one of the twentieth century's few Renaissance men. My favorite Alvarez hack was when he used muon imaging to 'X-ray' the Great Pyramid. He didn't find any hidden chambers, but later researchers did.
In the Alvarez mass-extinction hypothesis, he simply followed where the evidence led, unlike the supposed professionals in the field.
"The guy"? There were two guys, Luis Alvarez and his son Walter Alvarez, a geologist. It wasn't just a case of a famous physicist meddling in a field he knew nothing about.
Edit to add: checking Wikipedia, I see that chemists Frank Asaro and Helen Michel are also credited as part of the core team, although it still gets called the "Alvarez hypothesis".
Except the evidence didn't lead there. The fossil record is not consistent with sudden mass extinction. We have examples of sudden mass extinction events in Earth's history. The K-T boundary doesn't look like those. There were and still are many different lines of evidence pointing in incongruent directions. Alvarez pointed at layer of iridium and said "it must be a cosmic strike; it cannot be anything else" and derided anyone who still bothered publishing evidence to the contrary.
Except.. there are a lot of iridium layers in the geologic record. These things tend to happen every 10-20m years. The most recent is probably the Eltanin impact about 2.5m years ago. The K-T impacter is definitely one of the largest, but not by as much of a margin as you might think. The mere presence of an impact within a million years or so of the mass extinction is neither surprising nor damning evidence, and Alvarez never bothered to make the case beyond that.
And if you look at the history of mass extinctions, most of them are triggered by climate changes from geologic events. Pretty much every time there's massive vulcanism, most of the species on Earth die out. And hey, what do you know, there was a truly epic scale volcanic eruption going on for millions of years right at the same time! What a coincidence.
The Chicxulub impact is certainly part of the story of the extinction event that killed off the dinosaurs. But the evidence isn't there to assert that it is the whole, or even the most important part of the story.
I wouldn't be qualified to take sides in this particular pissing match, but still, the point stands. Alvarez was "directionally correct", and the existing researchers were not. He moved the field forward, while they did not.
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