When we look back at the history of science, it’s tempting to imagine that once the evidence was in, everyone immediately saw the truth. But the story of R.A. Fisher and smoking is a reminder that even the brightest minds can be led astray - not out of stubbornness alone, but because of the scientific limits of their time.
Fisher’s genetic hypothesis
By the mid-20th century, evidence was piling up that cigarette smoking caused lung cancer. Yet R.A. Fisher - one of the greatest statisticians and a founder of modern genetics - remained unconvinced. Instead, he proposed a different explanation: the correlation between smoking and lung cancer might be due to genetics.
In his view, some people could be genetically predisposed both to form the habit of smoking and to develop lung cancer. If true, then smoking wouldn’t be the cause at all, but just a marker of an underlying genotype.