We all have them, though it’s puzzled biologists for a long time as to why we do. I’m talking about that odd little groove found below your nose that runs to your top lip. Technically, it’s known as your philtrum and it’s as ubiquitous to the human face as the nose or eyes. But what is it, and why the hell do we have it? Well fascinatingly enough, it all relates to how faces are formed within the womb during development.
What the philtrum marks is the location where different parts of the face merge into one. “It is the place where the puzzle that is the human face finally all comes together,” explains Dr Michael Mosley in a clip from the BBC program Inside the Human Body. “The three main sections of the puzzle meet at your top lip, creating the groove that is the philtrum.” The development of the face happens between months two and three of being in the womb, and if the face doesn’t form during this window, for genetic or environmental reasons, then it never will.
You can watch Dr Mosley explaining this below, as well as see an astonishing video of the face as it forms in the womb and how all the pieces eventually come together to create a recognizable human face, taken from scans of a real baby developing.