Current theory about the shape of the human face just got a big punch in the mouth.

Two University of Utah researchers proposed Monday that the face of the ancestors of modern humans evolved millions of years ago in a way that would limit injuries from punches during fistfights between males.

Their theory, published in the journal Biological Reviews, is presented as an alternative to a long-standing notion that changes in the shape of the face were driven more by diet — the need for a jaw that could chew hard-to-crush foods such as nuts.