It may seem frustrating to have so many imperfect competing hypotheses, but that’s part of the joy of chins: They reveal something about how scientists think about evolution. Some see the sculpting power of natural selection in everything, and view chins as surely some kind of adaptation. Others see natural selection as just one of many evolutionary forces, and so gravitate towards a spandrel-based explanation. “The chin is one of these rare phenomena in evolutionary biology that really exposes the deep philosophical differences between researchers in the field,” says Pampush.