Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Pardon my ignorance ... A lip is apparently a very sensitive tactile device - as it at-least serves to warn it's owner they may just be about to consume something that could cause injury. Primates (including humans), dogs, cats, sheep, buffalo, elephants, some fish, octopodes - to name a few, have a lip.

How have lips evolved to be nearly ubiquitous across animals? Why have they evolved into a beak/bill in some birds & fish? What niche/purpose do they fulfill?

share|improve this question
"Why have they evolved into a beak". Is this true? I would guess that lips and beaks evolved to perform occasionally similar functions, but from very different structures, and so lips have not evolved into beaks. – Oreotrephes Jul 29 '13 at 23:45
Maybe lips are (nearly) ubiquitous in extant mammals because they all inherited lips from a common ancestor. – kmm Sep 25 '13 at 19:18

I think what you are looking for can be found and pretty easily.

To summarize, lips:

  • Mainly useful in mammals
  • Food intake
  • Articulation
  • Tactile organ
  • Erogenous zone
  • Facial expressions


  • Found in birds
  • Feeding
  • Defense
  • Manipulation of objects
  • Communication
  • Heat exchange
share|improve this answer

What is a lip(s)? A set of muscles around an orifice that can close said orifice.

How about a way to close a hole so that not everything can get in but what we want - to eat, breathe, drink?

The fact that they are also sensitive is just needed so that you can more precisely operate them for whatever need you have.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.