Link #154: Only Humans Have Lip Borders

Image credit: AZAdam/CC BY-SA 2.0


Chain of Facts - A Connection of Facts

Link #154: Only Humans Have Lip Borders

Image credit: AZAdam/CC BY-SA 2.0

In our last article, we talked about the smartest animal on the planet. It was a Border collie known as Chaser who understood more than 1,000 different words and concepts. While the intelligence of this Border collie is much higher than all other animals on the planet, it comes nowhere near humans.

This intelligence makes humans unique on the planet. However, this isn’t the only thing that makes us humans stand apart from the rest of the planet. In fact, we are unique in some useless ways too. For example, did you know that it’s only humans who have borders on their lips?

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Are Humans Really The Only Ones With Lip Borders?

 Vermilion Border
Image credit: Mikael Häggström/CC0

It’s true. Homo sapiens are alone on the planet when it comes to having borders on lips. While you’ll find numerous animals on Earth with lips, you won’t find any animal that has border on its lips.

The border on human lips is called the vermilion border. It’s not exactly a border. Instead, it’s an acute separation between the skin of the lip and the skin on the rest of the face. In the majority of cases, the vermilion border is well defined with clear demarcations.

The most interesting part of the lip border is that there isn’t any clear purpose for it either. Even though research material on the vermilion border is sparse, it’s still surprising that no scientist in the world has been able to figure out why this border exists.

Why Are Our Lips Red Anyways?

Red Lips
Image credit: meemal/CC BY 2.0

Your vermilion border, like the rest of your lips, is most probably red. This is true for most fair skinned people. However, even if your lips are not red, their colour will be different from the rest of your skin. In the majority of cases, the colour of lips is lighter than the rest of the skin.

This happens because the skin on your lips is different from the rest of your face and body. For instance, the skin on your lips will only have up to five cellular layers. Your facial skin, in contrast, has up to 16 cellular layers.

Having fewer cellular layers causes two things. The first is that it reduces the number of cells that produce melanin in the region. Melanin is the pigment that gives your skin colour.

The second fallout of thinner skin on lips is that it brings blood vessels closer to the surface. Since these blood vessels carry blood, their closeness to the surface gives lips their red colour. People who don’t have red lips only differ in the sense that they have more melanin producing cells.

There’re some other consequences of the thinness of the skin on the lips too. For instance, because there are only up to five cellular layers, it prevents hair follicles and sweat glands.

Hair follicles are responsible for the growth of hair which is why there is no hair on the lip. Similarly, sweat glands are responsible for creating sweat which is why lips never sweat.

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