Almost everyone knows Sherlock Holmes, the fictional super-detective famous for spotting tiny clues and making astonishing deductions. But few know that those skills were based on a real person: Joseph Bell, a Scottish surgeon whose powers of observation were so remarkable that they seemed almost supernatural.

Bell taught medicine at the University of Edinburgh, where one of his students was a young Arthur Conan Doyle. Bell believed that seemingly insignificant details could reveal an enormous amount about a person. He studied patients’ clothing, mannerisms, facial expressions, accents and physical characteristics, then used those observations to deduce their occupations, backgrounds and ailments. In one famous demonstration, Bell correctly concluded that a patient claiming to be a shoemaker had actually served in the military, eventually exposing evidence that the man was an army deserter. 

Conan Doyle was fascinated. He later said it wasn’t enough simply to tell readers that a character was clever. You had to show that cleverness through examples, just as Bell did every day in the hospital wards. When Conan Doyle created Holmes, who first appeared in print in 1887, Bell’s method of turning tiny observations into larger conclusions became one of the detective’s defining characteristics. 

And Bell wasn’t merely a medical detective. He also worked with police surgeon Henry Duncan Littlejohn on criminal investigations, bringing the same meticulous approach to real crimes. Bell even followed the Jack the Ripper murders and claimed to have identified the killer, although the name of his suspect has apparently been lost to history.