A human, running like a quadruped, is creepy.

Artist Rui Martins created this animation

about a year ago. 127 years ago

Eadweard Muybridge shot these real images of a child with infantile paralysis

walking on all fours. Walking upright

looks less unnatural, our bodies are particularly well suited for it. It's one

of the things

the bulbous and prominent

human bottom helps us do. But let's get to the bottom

of a linguistic mystery. Why is the bottom

called a bottom, when it's in the middle of the body?

Your feet and legs are almost always

at the same level or below your bottom. I mean, except for

Navasana, the yoga boat pose, your bottom is

anything but the actual bottom of your body.

Unfortunately, there is no clear-cut

answer, but there are butt loads of cool things to learn

about butts. A buttload is not just a joke amount. It is a very specific

unit of measurement. Historically, it was used to describe the capacity

of a wine cask. A butt is about

477 litres, which means,

given the average volume of solid waste

the rectum holds, when a person says they have a

buttload of something... Technically,

they are saying they have enough of that thing to fill

3,200 butts. Using the word

bottom to refer to your posterior is relatively new.

Cedric Watts has presented evidence that in the late 16th century bottom could

connote the human rear end,

but the first published use wasn't until 1794

in Erasmus Darwin's 'Zoonomia'.

The word bottom comes from words meaning

'foundation', 'the lowest level'. But when standing or sitting,

the soles of your feet are more properly

at the bottom, and, sure enough, sole also means

'foundation', 'bottom'. What's going on here is probably a combination

of torso-centric thinking and euphemism.

Bottom is a nice word for a sometimes

dirty part and your bottom is the bottom of your digestive tract and

the bottom of your torso, the bottom of your body,

if you exclude your limbs. For Prince Randian,

a man born in 1871 in British Guiana,

the bottom was the bottom.

Because of tetra-amelia syndrome, he was born with no

limbs at all. In 1889 P.T. Barnum brought him to the United States to perform

in carnivals. And you can see him light a cigarette with no arms

or feet in the 1932 film

"Freaks". Bottom is just one of many words we have for the posterior,

the rear, the backside, derrière, bum,

buns or, in reference to its round shape, moon.

Which is why exposing your bare buttocks

is known as mooning, an offensive gesture.

The earliest known instance of mooning was recorded by Flavius Josephus. It occurred

in 66 A.D.

A Roman soldier mooned

a group of Jews headed to a temple in Jerusalem.

His act of mooning spawned a riot and the subsequent

overreaction on the part of the Roman military led to the

deaths of thousands of people.

If you get mooned you will,

just like a guy who died September 14th, 1865 and is now buried in West Laurens, New York,

Seymour Butts. At least he didn't share his name with a former

representative of New Hampshire's

second district. The word 'bum'

predates the use of the word bottom for the rear by quite

a lot. It's believed that the word bum originated as an onomatopoeia for the

sound of

buttocks slapping against a flat surface.

Seriously. Lazily sitting around on your

bum all day gave American English the word

bum, a loafer, an idle person.

And bum's connotation of uselessness, poor quality

caused it to lend itself in the late 1960s to the word

'bummer', an experience that was worthless -

a letdown. But to be clear, your butt

is a bottom, kind of. It's a bum

but it is not a bummer. Your butt is magnificent, an example

of what makes the human body so different.

Its shape comes from the gluteus maximus and gluteus medius muscles as

well as a layer

of fat. That layer of fat makes the bottom a great cushion

for sitting. Other animals have to sit

by resting weight on their legs because they lack the nice

bulbous butt of the human. Evolutionary psychology suggests that our attraction to full

firm bottoms on potential mates was probably

naturally selected. People in the past who liked

big ol' bottoms probably spread their genes quite

well. They probably had a lot of reproductive success because the calle

pigeon bottom

is a sign of health and youth. A bottom full of shapely fat

is a great energy reserve. That energy can come in quite handy if

food suddenly become scarce or during pregnancy

or breast feeding. There's a great reddit thread you can read if you'd like this

evolutionary psychology approach wrapped up in a

Sir Mix-a-Lot's "I like big butts" package.

Because we are bipedal in order to keep our torsos balanced while moving

we require relatively giant and prominent

muscles in our bottoms, muscles that are so prominent

we have, compared to other apes, very defined intergluteal clefts.

Butt cracks. This makes

certain hygienic practices more common in humans

than other animals. But those prominent muscles

are worth it. Compared to horses and other quadrupeds

humans can reach impressive long-distance

aerobic endurance running speeds.

This is Katarina Johnson-Thompson, an Olympic athlete from Great Britain

and an excellent example of the fact that humans

are the running animal.

Hi Michael.

Hi Katarina. Take a look at this.

I'll make it brief, but above and beyond other animals, humans can:

sweat to efficiently dump body heat, we have short toes to provide more efficient

force over long periods of running, our short neck ligaments keep our head perfectly

stable when running,

our uniquely well-developed Achilles tendon converts elastic energy into

kinetic energy

very well and our tall narrow waists provide great counter rotation as our legs

swing backwards and forwards. I like how PZ Myers

sums it up: "Over long distances, the average

speed sustained by a horse is less than that of the human,

which means that a well-trained conditioned human being

can keep up with, or even outrun, a horse

if the race is sustained long enough."

For this reason endurance running is still practiced by a few people on Earth

as a form of hunting and it may have been vitally important to prehistoric people.

Before domesticated animals and projectile weapons and traps,

humans caught animals for food in an incredibly

athletic way. David Attenborough documented this practice fantastically.

You should

definitely watch this clip. An animal will sprint away from running human

hunters but eventually

have to rest. Humans, on the other hand, though slow in the short run

can keep going. Like the tortoise, they eventually beat

the hare and can walk right up to the exhausted and overheated

animal to kill it. We don't have

dangerous claws or massive teeth and we can pretty much

only outsprint vegetables.

But, in the long run, thanks to things like our impressive

butts, we have superior endurance

when it comes to running. It may be called a bottom

but it's at the top of the list of things that make the human body amazing.

This video was inspired by Sport Relief.

A great cause that uses sport to raise money for vulnerable people here in the

UK and abroad.

Check the description of this video to learn more and watch their interactive

video about how you

can help out and get involved. But wait a second,

if our bodies are so well developed for endurance running

how come we don't all run marathons?

How come we don't all enjoy running

or do a lot of it? Well, the thing is all of this running specialization was

naturally selected

because it helped our prehistoric ancestors survive.

Actually enjoying all of that running was not naturally selected, it was just a part of their

daily lives. But that doesn't mean that today you can't

get off your butt, use your butt and be proud of it.

The next time someone calls you a butthead say

"thanks, I always knew my head was a superlative object that set me apart from

the animal kingdom."

Katarina

And as always,

thanks for watching.