It’s easy to assume that humans evolved bony chins because they offer some form of additional facial protection—but the theory underscores a common misunderstanding when it comes to natural selection. And when it comes to humans, the clearest example of a spandrel is our chins. However, past theories generally rest on natural selection as the main influence on lower jaw evolution. Essentially, they examined the cranial anatomy of apes and humans to show that correlation does not always equal causation. “Just because we have a unique feature, like the chin, does not mean that it was shaped by natural selection to enhance an animal’s survivability,” argued Cramon-Taubadel.