“Don’t throw out the baby with the bath water,” Yung-Chi Cheng, a pharmacology professor at Yale School of Medicine, says with a chuckle. “People forget that one of the oldest, most effective, scientifically proven drugs came from traditional medicine—aspirin.” The ancient Egyptians used dried myrtle leaves to treat aches and pains, and Hippocrates, the fourth-century B.C. Greek physician, considered the father of Western medicine, prescribed an extract of willow bark for fevers. But it wasn’t until the 1800s that European scientists figured out that the active ingredient in both is salicylic acid and synthesized it. Today aspirin, at pennies a dose, is arguably the world’s most cost-effective drug.