Millions of years of fist fights have altered the human face to leave men's jaws more robust than women's, a study has found.
Evidence suggests it evolved to minimise damage from bruising altercations after our ancient ancestors learned how to throw a punch.
Researchers studied the bone structure of australopiths, ape-like bipeds living four to five million years ago that pre-dated the modern human primate family Homo.
They found that australopith faces and jaws were strongest in just those areas most likely to receive a blow from a fist.
It is a legacy that continues to this day, helping to explain why men's faces are more robust than women's, say the scientists.