Good morning, John.

It is time for another Bizarre Beasts. Welcome back to Bizarre

Beasts: Season Zero. We’re on a year-long journey to remaster  the old Bizarre Beasts episodes from   Vlogbrothers with corrections, updates,  and new facts about these beasts. Make sure you stick around for  the pin set announcement and for   even more new material about  this video’s Bizarre Beast. This time I've taken a different tactic  and I am approaching an animal that you   are familiar with, but that  is way weirder than I thought.

Just because something is common doesn't mean  it's not bizarre, and John, horses. Horses! [♪♪INTRO♪♪] They can't puke. They can't  breathe through their mouths.

I mean, I'm not saying they  aren't beautiful animals,   though, in part, they were bred to be beautiful. It's important to note that  there are kinda no wild horses. Now, there's two reasons for that kinda.

First, there are lots of feral horses. These are wild individuals  of a domesticated species   and there are tens of thousands  of feral horses in North America. But the second reason it’s  a kinda is more interesting.

In Mongolia, there's a species of horse that went  extinct in the wild but has now been reintroduced. It's called Przewalski's Horse, or the Takhi. And, yep, I did pronounce that in the  fairly common, Americanized way in the   original video, but it’s more correct  to pronounce it as ‘shev-all-ski’s’ horse.

And it's often called the  last wild horse, but first,   this probably isn't the horse that  modern horses were domesticated from,   at least not entirely, and second, genetic  studies indicate that the Takhi might   actually be a feral descendent of an ancient  domesticated horse, but here's the thing. For thousands of years, wild  horse herds and domesticated   horse herds existed in the same spaces. So there isn’t really a clear sharp line  between domesticated horses and wild horses,   but the Takhi with its short legs  and zebra-like mane is one possible   version of what horses looked like  before we got our hands on them.

And if we want to know whether or not modern domesticated horses are descended from Przewalski’s Horse,   recent research indicates they’re not the direct ancestors of the modern horse, they’re  maybe more like their ancestor’s cousins. Another big piece of the kinda no  wild horses thing is the tarpan,   a wild horse that is now entirely extinct,   and we have like, one photo that I know of,  but also definitely this one drawing of. Or we could look to cave paintings,   because these are actually the only images  we have of pre-domestication horses.

Now, we often think of horses as being a  Eurasian thing, but they actually evolved   in North America before barely getting out over  the Bering land bridge before going extinct. And then we humans brought them back  because they were useful and then they   escaped and became wild and so that famous North  American mustang is kind of an invasive species,   but it's also kind of a reintroduced species. As far as I know, that is the only  example of that ever happening in history.

But I could totally be wrong! Let me know in the comments if  you know of another example. All that is very cool, but the thing that  really freaks me out about horses is their legs.

Okay, a thing you have to understand,   all terrestrial vertebrates  have a really similar body plan. We have two forelimbs and we have two  hind limbs and we have a middle trunk   and we have a head on top, and at  the end of each limb, we have feet. Okay, in a few species, there are hands,   which are just like feet that you don't walk on.

Or, in bats, you have feet that you fly with. Birds, their feet just became this like,  little nubbin on the end of their arms. This sounds strange, but to  an evolutionary physiologist,   like, hands are just feet that you type with.

Whatever, I don't have time to  talk about how weird hands are. The point is, there's a very  similar body plan in all animals. In us, we have bone, bone foot.

In ostriches, bone, bone, foot. In mice, bone, bone, foot. In Tyrannosaurus rex, bone, bone, foot.

But then, you've got a horse leg. That's bone, bone, bone, bone, bone, foot? Where's the–where's the foot?

The species in Equus, which includes horses  and zebras and donkeys are just not closely   related to any living species, but in  the fossil record, we can see their toes   becoming less and less necessary until they  are left walking around on just one big toe. Those two top bones are leg bones. All of the rest of these bones  are foot.

They're foot bones. And the horse hoof is just a big old toenail. So the next time you see some  beautiful galloping stallions,   just note, they're all just  walking around on one finger.

If you look close enough, John, everything is a bizarre beast.   If you missed the horse pin the first time  around, our Season Zero pin set is now available! This set includes all 12 of the animals that  we began this Bizarre Beasts journey with on   Vlogbrothers, as well as a bonus pin of our  very first Bizarre

Beast: the Mola Mola! To get the Season Zero Pin set and everything  else Bizarre Beasts, visit bizarrebeastsshow.com! One of the courtship rituals of the bizarre beasts better known as humans is Valentine's day, and we've turned the art of some of our favorite beasts into valentines. You can order them now at BizarreBeastsShow.com to tell your crush you "Lek" them.

If you want to know what horses  looked like back when they still   had the standard bone-bone-foot tetrapod body  plan, we have to take a look at Sifrhippus. It’s among the oldest fossil evidence we have  of the family that today includes horses,   asses, and zebras, and it lived in what is  now Wyoming around 55 million years ago. It weighed about 5.6 kilograms  or 12 pounds on average,   and ate mostly leaves, not  grasses like modern horses.

And it had four toes on its front  feet and three toes on its back feet. You might think, based on what  their legs and feet look like,   that horses are most closely related  to animals like deer and antelope. But that would be wrong!

Horses, rhinos, and tapirs are  actually part of a group called   ‘odd-toed ungulates…’ even though they  don’t always have an odd number of toes. We already talked about how horses run around  on a single toe, but rhinos have three toes on   each foot, and tapirs have four toes on their  front feet and three toes on their back feet. And things like deer and antelope are  part of a separate group of ungulates   called the ‘even-toed ungulates,’  because they and their relatives   typically have two or four toes  on each foot, covered by hooves! [♪♪OUTRO♪♪]