Teeth from ancient human ancestors suggest that females joined new social groups once they reached maturity

Fossilized teeth of early human ancestors bear signs that females left their families when they came of age, whereas males stayed close to home.

A chemical analysis of australopithecine fossils ranging between roughly 1.8 million and 2.2 million years old from two South African caves finds that teeth thought to belong to females are more likely to have incorporated minerals from a distant region during formation than those from males.

"What that's telling us is that the females grew up somewhere else and they died in the caves," says Julia Lee-Thorp, an archaeological scientist at the University of Oxford, UK, and a co-author on the study, published today in Nature. "It's a very small clue, but it's something that is at least hard evidence for what we really didn't have before."

The shape of ancient human families has been the subject of speculation, based mainly on differences in the relative size of male and female fossils, and the behavioural patterns of our primate relatives. Female chimpanzees, for instance, typically leave their social group once they hit maturity. Among gorilla groups, which are dominated by one large male 'silverback', both males and females tend to strike out.

Modern humans, who are influenced by relatively recent cultural practices such as marriage and property ownership, are difficult to compare to our early ancestors, lead author Sandi Copeland of the University of Colorado at Boulder said in a press briefing.

Read more about this type of forensic dentistry here