Back in the 90s, I spend a fair amount of time reading books about the Cretaceous extinction, including several by paleontologists arguing that the Alvarez impact hypothesis was a snare and a delusion, people like Charles Officer, Gerta Keller, and Dewey McLean. More recently, Donald Prothero, in After the Dinosaurs: The Age of Mammals.
Generally speaking, I thought the paleontologists were a waste of space: innumerate, ignorant about evolution, and simply not very smart.
None of them seemed to understand that a sharp, short unpleasant event is better at causing a mass extinction, since it doesn’t give flora and fauna time to adapt.
Most seemed to think that gradual change caused by slow geological and erosion forces was ‘natural’, while extraterrestrial impact was not. But if you look at the Moon, or Mars, or the Kirkwood gaps in the asteroids, or think about the KAM theorem, it is apparent that Newtonian dynamics implies that orbits will be perturbed, and that sometimes there will be catastrophic cosmic collisions. Newtonian dynamics is as ‘natural’ as it gets: paleontologists not studying it in school and not having much math hardly makes it ‘unnatural’.
One of the more interesting general errors was not understanding how to to deal with noise – incorrect observations. There’s a lot of noise in the paleontological record. Dinosaur bones can be eroded and redeposited well after their life times – well after the extinction of all dinosaurs. The fossil record is patchy: if a species is rare, it can easily look as if it went extinct well before it actually did. This means that the data we have is never going to agree with a perfectly correct hypothesis – because some of the data is always wrong. Particularly true if the hypothesis is specific and falsifiable. If your hypothesis is vague and imprecise – not even wrong – it isn’t nearly as susceptible to noise. As far as I can tell, a lot of paleontologists [ along with everyone in the social sciences] think of of unfalsifiability as a strength.
There were lots of examples. In his book, Donald Prothero argued that the rudistid clams – the main reef builders in the Cretaceous – had gradually declined and finally disappeared a half million years before the K-T extinction: but that was noise. When people looked harder, they found that those rudistid clams were around until the Earth got walloped. He did this a bunch: every error or missing piece of data was evidence against the Alvarez hypothesis.
People do the same thing with conspiracy theories. X is impossible, so the standard account must be an elaborate lie, or at least wrong. You construct a chronology of the crime and prove that you [Edgar Smith] couldn’t have (quite) gotten from here to there and strangled the girl in the time available. Of course the time accounts contains errors – real life accounts usually do – and the author of Brief Against Death was, shall we say, motivated. Not motivated enough to avoid another kidnapping and attempted murder upon his release, though.
When people argued that the Black Death couldn’t really have been caused by Yersinia pestis – their models suggested that it spread too rapidly in rural areas to have that cause – well, they were relying on models built of sand. We’ve dug up bodies from mass graves in London and sequenced the pathogen DNA – Y. pestis, all right. When people claimed to have seen the marks of prebirth exposure to syphilis in skeletons carbon-dated to a bit before Columbus [ruling out a New World origin], they didn’t realize that those skeletons came from a fishing community, and that fish often incorporate carbon from upwelling deep water, carbon that’s been hanging out downstairs for 20,000 years: pretty low in C-14. But the idea was silly from the beginning: syphilis spreads like wildfire: coming from America could explain why it never spread over the Old World before 1494.
There are cases in which a single ‘fact’ can sink a theory, for example when you violate a conservation law, but you have to think hard and, usually, check it several times. it needs to be a situation that we understand well enough to say what’s impossible, or close to – fairly common in physics, not so common in most other situations.