Name: なぜ私たちは皆、異なる髪を持っているのでしょうか？ (Why Do We All Have Different Hair?)
Uploaded: 2021-01-14T07:56:16.000Z
Duration: 4 min 43 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Give me a head with hair, long beautiful hair,
shining gleaming steaming flaxen waxen.

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

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

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

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

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

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

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

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

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

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.

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

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

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