The researchers discovered that more than half of the smaller individuals analyzed, inferred to be females, may have been foreign brides, possessing strontium isotope compositions that did not match the landscapes where they made their homes. On the other hand, about 90 percent of the larger presumed males apparently grew up where they lived.

“We knew that if we knew how early hominids used their landscape, we could find out something interesting about their social structures or home-range sizes or other aspects of their lives difficult to ascertain from fossil teeth and bones,” Copeland said. “Here we have the first direct glimpse of the geographic movements of early hominids.”

These findings suggest that females were more likely than males to roam away from their birth groups across the South African savannahs. Males may have stayed in a relatively limited zone nearly 12 square miles (30 square kilometers) large, the researchers calculated based on the isotopic fingerprints of the surrounding bedrock.