Not only that, but rapamycin had worked even though the mice were already middle-aged when they took it. The study had started late, because the team’s pharmacologist had spent months trying to get the drug into mouse feed in a chemically stable way. By the time he figured it out, the animals were already nearly twenty months old, the mouse equivalent of about sixty human years—too old, according to conventional wisdom, for an anti-ageing drug to have any effect. Yet still the stuff had increased both the average and maximum overall lifespan of the animals by 9 percent for males, and 14 percent for females.