Alexander Fleming's dodgy cleaning habits helped him discover penicillin in 1928. The bacteriologist was cleaning Petri dishes when he noticed mold growing on staphylococcus (staph) bacteria. The mold, Penicillium notatum, killed the staph around it and Fleming realized he stumbled on a treatment for bacterial infections. Fleming's discovery revolutionized medical practices, but researchers found that he wasn't the first to accidentally discover antibiotics. Ancient Nubians regularly drank antibiotics in their beer more than 2,000 years ago.
In 1963 George Armelagos, a biological anthropologist, and some colleagues uncovered Nubian mummies. The Nubians lived between 350 AD and 550 AD in modern Egypt and Sudan. Armelagos began peering into microscopes to examine Nubian bones and understand osteoporosis, when he noticed the mummies exhibited high levels of tetracycline, an antibiotic once used to treat cholera, but not available until 1950. (Now, it is mostly prescribed to treat acne.) He was curious why there were such high levels of the antibiotic and thought it came from contamination. He took bone samples and asked a lab to dissolve them, extracting tetracycline. He found that the Nubians consumed so much of the drug that remnants lingered in their bones. This was no freak contamination. (The image at left, taken under UV light, shows the tetracycline on the bones—the green is the tetracycline.)
Armelagos discovered that grain stored underground became moldy with Streptomyces, which produces tetracycline. High heat from baking bread, for example, would kill the small amounts of it. But fermenting the grains would promote rapid growth of tetracycline—Nubians prepared gruel and beer with fermented grains. Armelagos found that beer drinking started young and discovered traces of tetracycline in babies from mothers' breast milk. Armelagos suspects that the Nubians realized the beer and gruel made them feel better but had little idea why.
Some of Armelagos' students made a home-brewed beer with Strep bacteria, like the Nubian brew. It tastes sour and looks green (perfect for St. Patrick's Day and Strep throat). Don't worry about ingesting extra antibiotics when drinking beer, though—most beers undergo pasteurization, killing bacteria.