The origin of laughter, smiles and tears

“My best guess, strange as it might sound, is that our ancestors were in the habit of punching each other on the nose. Such injuries would have resulted in copious tear production. And there is an independent line of evidence to suggest that they were common. According to recent analysis by David Carrier and Michael Morgan from Utah University, the shape of human facial bones might well have evolved to withstand the physical trauma of frequent punching.”