Why are your lips red and not the same colour as the rest of your skin
LIPSTICK?
maby there is just more bloodflow to the lips?
Desmond Morris contends that lips are sexual advertisement and they are red because the lips of the labia are red (generally speaking). He cites the case of the mandrill, a type of baboon with a highly colored face and similarly colored nether regions.
Physically, their red color comes from the skin being of a different type and much thinner there.
If I’m not mistaken, the lips are clad not by skin, but by mucosa, the delicate tissue that clothes the inside of your body cavities. It’s highly vascular (has lots of blood vessels very close to the surface), which for all I know is why your lips crack and bleed in the winter but the rest of you doesn’t.
While it’s a sexual advertisement (and this is also why lipstick is popular) it’s also a “notice me” or species identifier. People’s facial featurea allow us to recognize one another as a member of the same species, therefore available for breeding. As people eveoved, and sensory input became largely confined to the face and genitals, the lips bacame propotionaly larger in regard to the rest of our face. Species that don’t use their mouths for kissing as much( or which are less sexaully competitive) tend not to have differentiated lip color or structure.
Also, since we put (among other things) food into our mouths via them, it makes sense that they be very sensitive mucosa rather than skin, so as to alert us to any toxcity before we eat something.
Most lips aren’t all that red in the first place. Take an objective look, I think you’ll see there is some reddishness, but not as much as you think.