HAIR!

It's Monday, so we're answering viewer questions today, and on our Why Do We Have Warts video,

Saihan, Elyse, and TheGamingWookiee all had questions about hair!

Different types, why do some have more than others, and why do we even need it!

Firstly, hair is a natural part of being human.

We tend to associate it with our head, face, armpits, pubic regions, and legs; but it's

actually everywhere.

We like to think of ourselves as a naked ape, but we have the same number of hairs on our

body as a chimpanzee; or around five million hairs.

Before you ask, hair and fur are the same thing.

You and your fuzzy dog or cat all have hair made of the same stuff: keratin.

Your skin is made of layers -- the epidermis, then the dermis underneath.

In the dermis, cells are constantly dividing, and the older cells are pushed out of follicles

creating hair all the time.

On chimpanzees, hair protects skin from the sun, and provides warmth.

When you take into account thermoregulation, hair was a way to keep that body warmth in

naturally!

Though, in modern humans it still protects our head from the sun's rays, and allows sweat

to travel along hair shafts and evaporate, cooling us down, but it doesn't keep our bodies

warm anymore.

There are many different TYPES of hair.

Fetuses in the womb grow hair called lanugo; though it usually recedes from the body before

birth, it doesn't always.

A comforting reminder of our primate history, perhaps?

After birth, we humans grow soft, fine, unpigmented vellus hair all over our bodies, though thicker,

pigmented hair on the head, eyebrows, eyelashes, and so on, is called terminal hair.

During puberty, some of vellus hair transitions to terminal hair or androgen hair -- named

for the sex hormones that cause them.

On the face, and chest for men and in the armpits and pubic regions for both men and

women.

What hair you get depends a lot on your genes.

A 2009 Cambridge study found the genes for hair were 85 to 95 percent inherited, though

some can be affected by the environment.

Hair curls for two reasons.

First, an asymmetrical, or oval-shaped, follicle will force a curvy hair to emerge; circular

follicles produce straight hair; but a specific cellular receptor called epidermal growth

factor receptor regulates the growth of hair.

If the EGFR puts too much keratin on one side of the hair shaft as it grows, it will come

out curly!

Hair is a holdover from our ancient ancestors.

As we evolved, our genes mutated, and hair thinned on some parts of the body, but the

why in some places and not others is an evolutionary mystery!

Perhaps hair lessened for social interaction, to better see the eyes and face; or as we

became more upright and mobile evolution favored those with just enough to reduce skin-on-skin

friction in pubic regions and armpits; or perhaps ancient humans spent more time in

the water, and hair wasn't as useful there except on the exposed parts of the head.

Perhaps, hair remains in the pubic regions similar to eye, head, nose, and ear hair -- to

block dirt and other deuterium from the genitalia or to keep UV rays away from the sex organs?

Or maybe it allows pheromones to spread from the body for mating!

The Economist writes that perhaps mature women are more visibly hairless, on average, than

men because, at some point, hairlessness was selected by men as a sexually attractive trait;

a similar theory as to why human males have the largest average penis size of all primates.

Again, we don't exactly know.

What we DO know, is maintaining SOME, but not ALL body hair, may be due to parasite

detection.

A study from England's University of Sheffield found people with more body hair could detect

bed bugs more quickly than those with less.

Though by tracing the evolution of lice alongside humans, scientists determined we started trying

clothing on more than 170,000 years ago.

This was great for the cooler temperatures of the coming ice age; and when we started

to move from Africa into Europe.

More clothing, like thicker hair, means

more parasites… which is bad…

damn, this is a hairy topic.