Male faces 'evolved' due to fist fights
9 June 2014 Last updated at 12:01 BST
Male humans developed stronger facial features to protect against fist fights, according to scientists.
Researches at the University of Utah found that the facial bones of early ape-like bipeds, australopiths, were strongest in areas most likely to receive a blow from a fist.
Professor David Carrier, the evolutionary biologist who led the study, argued that the traits evolved as the need for males to fight increased.
He told BBC Radio 5 live's Breakfast: "There was a lot of fighting going on... Males competing for females but also males probably defending territory."