Maybe your grandmother told you that a smile is just a frown turned upside down. Sure, she could conjure one up with a freshly baked cookie, but a smile is a bit more complicated than Grandma might have realized.

That captivating upturn of facial muscles is a result of biological, psychological and sociological forces beyond our control. It’s an expression that goes back millions of years, but it can fire in a fraction of a second, says author Richard Conniff.

In a recent issue of Smithsonian magazine, the Connecticut writer has penned a biography of the smile. The scientific milestones include some events that are not so jolly.

– He traces its origins to a prehistoric plea directed toward the baddest guy in your cave that indicates: I’m harmless, so please don’t beat me.

– He recounts the first scientific exploration of smiles, as well as the contributions made by people who no longer needed their faces.

– He explains how an analysis of facial expressions has become one of our defenses against mass murderers.

Not a lot of grin-coaxing material there, but they all point to a common element: Our smiles – and other facial expressions – are often beyond our control.

–Entire article here courtesy of the Columbian.