Given our propensity to pop an antibiotic at the first sign of a sniffle—and much of the medical establishment’s willingness to gratify this often unwise habit—it’s hard to believe that the use of antibiotics to fight infection has been common practice for only a couple of generations. Like all medications, they come with risks of side effects, but in the right circumstances, antibiotics are truly wonder drugs.

They’re so wonderful, however, that we overuse them. The problem then becomes not just one of risky and/or unpleasant side effects, but of reduced efficacy.

The more frequently antibiotics are used, the better bacteria become at resisting them. It’s simple evolution—survival of the fittest bacteria. The fitter (stronger) the bacteria, the more compromised the antibiotics. In order to keep up with the demand of increasingly resistant bacteria, new compounds must constantly be developed. The old ones simply don’t work anymore.