Four eras of aging research

In 1920, a French surgeon named Serge Voronoff — Russian-born, trained under Alexis Carrel (who we will meet again shortly, and not in flattering circumstances) — began grafting thin slices of chimpanzee testicle tissue onto the testicles of elderly human men. He claimed this would restore youth, strength, and vitality. By the mid-1920s, he had performed the operation hundreds of times, set up a private monkey farm in Algeria to ensure supply, and presented the technique to the International Congress of Surgeons in London to an audience of thousands. The British Medical Journal ran a broadly favorable review.