Why Is Your BOTTOM in the MIDDLE?

Hey, Vsauce. Michael here. 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 becomes scarce or during pregnancy or breastfeeding. 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.