The theory is that by providing an effective way to treat syphillis, penicillin kick-started the sexual revolution in the 1950s, 10 years earlier than most people would assume. From EurekAlert:

Syphilis reached its peak in the United States in 1939, when it killed 20,000 people. “It was the AIDS of the late 1930s and early 1940s,” Francis says. “Fear of catching syphilis and dying of it loomed large.”

Penicillin was discovered in 1928, but it was not put into clinical use until 1941. As World War II escalated, and sexually transmitted diseases threatened the troops overseas, penicillin was found to be an effective treatment against syphilis.

“The military wanted to rid the troops of STDs and all kinds of infections, so that they could keep fighting,” Francis says. “That really sped up the development of penicillin as an antibiotic.”

Right after the war, penicillin became a clinical staple for the general population as well. In the United States, syphilis went from a chronic, debilitating and potentially fatal disease to one that could be cured with a single dose of medicine.

The basic idea, that people react to incentives, is not new. Just the incentive. And, in this case, I can’t help but think about the fact that treating syphillis might have made sex a lot safer for men, but women still had the risk of pregnancy to worry about. I wonder if the unequal shift in incentives had any social impact.