The evolution of the smile captured in 100 years of yearbook photos

We take it for granted that, when someone takes our photo, we should smile for the camera. But if Instagram had existed a century ago, it’s highly likely that stone-faced selfies rather than the beaming faces would dominate our photo feeds.

The smiles we turn on for the camera today are roughly 10 times bigger than the smiles photographed 100 years ago, according to new research from a team of computer scientists and software engineers at the University of California, Berkeley and Brown University in Rhode Island.

Why our frowns were gradually turned upside down is closely tied to the invention of the camera.