Scientists know a lot about Neandertals these days, from their hair color to their mating habits. Still, a basic mystery remains: Did they know how to start a fire? Archaeologists have long known that Neandertals, like the family pictured in this artist’s representation, used fire, but they could have merely taken advantage of naturally occurring lightning strikes and forest fires to supply the flames. Now, a new hypothesis about some odd Neandertal artifacts suggests that our distant cousins could indeed spark a fire from scratch. Excavations at the 50,000-year-old site Pech-de-l’Azé I in southwestern France have yielded blocks of manganese dioxide, which is abundant in the region’s limestone formations. Archaeologists previously thought that Neandertals used the substance as a black pigment to decorate their bodies. But a new team of researchers points out that charcoal and soot from their campfires would have made for easier and more accessible body paint. Plus, the Neandertals at Pech-de-l’Azé I appeared to have strongly preferred manganese dioxides to the other manganese oxides available in their environment, even though all of the closely related chemicals would have yielded the same color pigment. So what can manganese dioxide do that its relatives can’t? Start fires. Noticing signs of abrasion on some of the Pech-de-l’Azé I blocks, the scientists ground up bits of them to produce a powder. When they sprinkled that powder on a pile of wood, it lowered the temperature needed to initiate combustion to 250°C, making it much easier to start a fire, they report today in Scientific Reports. (Untreated wood failed to ignite at temperatures up to 350°C.) The researchers can’t rule out other possible Neandertal uses for manganese dioxide, including body decoration. But based on their experiments, they suggest adding fire-starting to the list.