Women leaving home, staying away from parent's house and finding and settling with a mate far away from home, looks like all these are not signs of a modernizing society, but a practice that existed around 2 million years ago.

A study of the teeth of 19 australopithecines from South African caves suggests that females were the one to move out and away from their birth places, whereas, larger males used to stay back surprisingly close to their home and kin, a report in News.sciencemag.org stated.

Debates have been on among researchers for several decades regarding human ancestors' living habits. Whether early human ancestors lived in close-knit social groups made up of related brothers and fathers, with new genes introduced by female mates gathered from other groups, has always been argued upon.

Matt Sponheimer, a co-author of the new study and a paleoanthropologist at the University of Colorado, Boulder calls testing models of the social organization of early members of the human family, known as hominins, a monumental task. It's as if someone told you to investigate the ecology of a giraffe but you were forbidden to observe them in the wild and confined to a room that contained a relatively small number of giraffe bones he says.

This study establishes that the females were the wanderers, leaving homes to join the males. This is the first direct evidence that exists for dispersal patterns among early hominins, says lead author Sandi Copeland, a paleoanthropologist at the University of Colorado, Boulder. The teeth came from two famous South African caves, Sterkfontein and Swartkrans. The study was conducted by measuring the ratio in the larger molars and canines, presumably from males.They found that before age 8, males fed primarily on dolomite soils around the caves. But at least half of the individuals with smaller teeth, presumably females, fed elsewhere, away from the local dolomite soils, when they were young. The pattern held for both species.

The findings, reported online in Nature, suggest that such patrilocal organization of social groups is ancient in human ancestors, perhaps dating back to the common ancestor we shared with chimpanzees, as some researchers had proposed.

The reason was not established as to why males would wander less than females, in a region where there were no natural barriers, said Copeland. Copeland and her colleagues have come up with an innovative way to test this model, and in the process, they have developed the very first direct evidence of early hominin social organization, says paleoanthropologist Peter Ungar of the University of Arkansas, Fayetteville. These results have implications for understanding australopithecine diet, group size, predator avoidance, and home-range size, paleoanthropologist Margaret Schoeninger wrote in an online publication in Nature on Thursday.