Scientists are painting the clearest picture yet of what life may have been like for Neanderthals living in Southern France some 250,000 years ago, and to do it, they’re using an unlikely day-to-day record of what their environment was like — their teeth.

A team of researchers showed that examining the teeth of Neanderthal infants could yield insight into nursing and weaning behavior as well as winter and summer cycles. The study even found evidence that the Neanderthals had been exposed to lead — the earliest such exposure ever recorded in any human ancestor.

The study from researchers Daniel Green, a postdoctoral fellow at the Harvard-affiliated Forsyth Institute; Tanya Smith, a former Harvard professor now at Griffith University in Australia; and Icahn School of Medicine at Mount Sinai researchers Christine Austin and Manish Arora, who is also a former postdoctoral fellow at the Harvard T.H. Chan School of Public Health, was recently publishedin Science Advances.

“Humans are very different from other apes,” said Green, one of the first authors of the study. “We are curious to understand what made us different in evolutionary history, and a lot of people have looked to the climate to understand those differences.