Penicillin

In 1928 Alexander Fleming notices that a mold, Penicillium, kills bacteria in a culture dish. He does not turn it into a medicine. Howard Florey, Ernst Chain, and their team in Oxford do that at the end of the 1930s, and wartime production in the United States scales it in the 1940s.

The contribution is an infection you can often stop. Before antibiotics, a cut or a childbirth could kill. Surgery stays limited because the surgery itself was a gamble. Penicillin, then a family of other antibiotics, is a major reason life expectancy jumps in the twentieth century. The population charts in the UN figures assume people survive infections that used to end childhood.

It is not a machine, and it is not why robots exist. It is on the timeline because the human side of the story changes here. Longer lives and lower child death are what make populations age, which is the slow shift discussed earlier, not a robot plan.

Overuse breeds resistance. The 1928 discovery is the start of a class of drugs, not a permanent victory.