system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the evolutionary significance of the ridge between our nose and mouth?

It's like an appendix. Nobody knows what it's for but sometimes it just decides to randomly kill you (in this case, people get a cleft lip).
gpt
It is called the "philtrum" and in other animals would carry moisture from the mouth to the nose through capillary action to keep it wet. In humans it is vestigial, but is formed by the fusion of the nasomedial and maxillary processes which if it fails results in a cleft lip.