“…I’d long thought that photographic technology had imposed that constraint: It’s harder to hold a smile than a grimace or smirk, and early film simply took longer to expose than people could hold an expression. Smile in a portrait and you’d wind up with a beautiful buccal blur.

“But an article by Nicholas Jeeves, recently published in the Public Domain Review, suggests that, when folks frowned, they did so for reasons as economic, social and historical as they were technological.”