Ever wonder why your hair goes gray? Researchers have long known that a slowdown in the production of melanin, the pigment that colors hair, is to blame. But they don’t know precisely what starts the slowdown, or how the mechanism varies between populations. Now, in a study that looked at the genomes of more than 6000 people from Latin America, researchers have identified 18 genes that appear to influence hair traits, including the first ever to be associated with graying. The gene variant linked to graying is found only in people with European ancestry, and it has previously been associated with light hair colors. Other firsts include genes associated with unibrows, eyebrow thickness, and beard thickness, the researchers report today in Nature Communications. The participants’ diverse backgrounds, which included African, European, and Native American ancestry, helped reveal relationships between genes and hair that would have been hidden in more homogeneous populations. Researchers say the discoveries could help investigators predict what suspects look like based on genetic evidence. Someday, they add, the findings might even help drug developers find targets for medications to delay hair graying.