Comment by robwwilliams
2 days ago
Fisher’s main scientific and statistical argument boils down to the possibility that gene variants that contribute to lung cancer are tightly linked with gene variants that make nicotine more or less addicting. By “linked with” he meant “close together on the same chromosome”. This kind of linkage can lead to strong a statistical association but without a mechanistic association (guilt by neighborhood).
Disproving this hypothesis is tricky, and Judea Pearl does a brilliant job of explaining the problem and its solution in his marvelous book: The Book of Why.
Fisher gets “assist points” for debilitating and killing millions, although full horrible credit goes to cigarette companies and their advertising co-conspirators.
Judea Pearl points out one cruel irony: The cholinergic receptor gene CHRNA5 that modulates risk of nicotine addiction also modulates lung cancer risk separately. To sort out the causality we now use Mendelian randomization.
Bottom line: smoking cigarettes does kill even when you tidy up the statistics and genetics.
To quote: "Ironically, Fisher was proven right, albeit in a very limited way: such genes [that increase both the tendency to smoke and the tendency for lung cancer] do exist."
The actual issue was not that (Cornfield wrote a paper in 1959 showing the effect was too small). It was that Fisher continued to repeat one finding in one study, despite that said finding had not been replicated in new studies (namely, lung cancer patients described themselves as inhalers less often than the controls), and continued to obstinately ignore all the other research coming out. But it was only 3 years between Cornfield and Fisher's death in 1962, so perhaps Fisher simply did not have time to change his mind.
> It was that Fisher continued to repeat one finding in one study, despite that said finding had not been replicated in new studies (namely, lung cancer patients described themselves as inhalers less often than the controls), and continued to obstinately ignore all the other research coming out.
Even if that finding were true, it could just mean that the cancer patients had stopped inhaling due to lung problems and underestimated how much they used to inhale.
If you asked me to estimate my caffeine, alcohol, fat, or sugar estimate from even 10 or 15 years ago, or how many steps per day I walked, I’m not confident I could give an accurate answer at all. If you asked me details about how I ate and drank — how fast I ate, how often I ate out, how quickly I replenished empty drinks, what percentage of the time I drank water with alcohol, or how often I cleaned my plate — I’m sure I’d be completely off the mark.