In 1824, a French sergeant was stabbed through the chest in a duel. Within minutes of his arrival at the hospital, doctors drained 20 ounces of his blood. Through the night, another 24 ounces. The next morning, 10 ounces.

Over the following 14 hours, he was bled five more times — losing nearly two liters total.

He survived. Physicians believed the blood loss was therapeutic. They thought it saved his life.

That’s an extreme example, but regardless, bloodletting is lindy. It’s persisted across 60 distinct cultures for over 3,000 years, emerging independently multiple times throughout human history. Medieval European barber-surgeons displayed bloodstained bandages wrapped around poles outside their shops — the origin of today’s red-and-white barber pole. Patients would grip wooden rods until their veins bulged while surgeons collected their blood in pewter basins.

Evolutionary biology explains some of it. Men evolved, essentially, for combat. Roughly 58 percent of paleoamerican males show evidence of violent trauma compared to 18 percent of females. Hunter-gatherer males adapted to regular blood loss from hunting injuries and interpersonal violence, but modernity eliminated most of these armed conflicts, leaving men with an evolutionary mismatch.

Aware of this, medieval doctors prescribed periodic bloodletting for men. It was all part of their theory of humors, which turned out to be wrong, though the observation that men might benefit from periodic blood loss is rooted in solid science.