Male faces 'buttressed against punches' by evolution

A new theory suggests that our male ancestors evolved beefy facial features as a defence against fist fights.

The bones most commonly broken in human punch-ups also gained the most strength in early "hominin" evolution.

They are also the bones that show most divergence between males and females.

The paper, in the journal Biological Reviews, argues that the reinforcements evolved amid fighting over females and resources, suggesting that violence drove key evolutionary changes.

Fossil records show that the australopiths, immediate predecessors of the human genus Homo, had strikingly robust facial structures.

For many years, this extra strength was seen as an adaptation to a tough diet including nuts, seeds and grasses. But more recent findings, examining the wear pattern and carbon isotopes in australopith teeth, have cast some doubt on this "feeding hypothesis".

"In fact, [the australopith] boisei, the 'nutcracker man', was probably eating fruit," said Prof David Carrier, the new theory's lead author and an evolutionary biologist at the University of Utah.

Masculine armour

Instead of diet, Prof Carrier and his co-author, physician Dr Michael Morgan, propose that violent competition demanded the development of these facial fortifications: what they call the "protective buttressing hypothesis".

In support of their proposal, Carrier and Morgan offer data from modern humans fighting. Several studies from hospital emergency wards, including one from the Bristol Royal Infirmary, show that faces are particularly vulnerable to violent injuries.