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Evolution of Horses and Donkeys

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Cours équin : introduction aux soins et à la gestion de base

Université de Floride

4.9 (452 notes) | 24K étudiants inscrits

There are over 100 million horses, donkeys and mules in the world today and owners of these animals can be found on almost every continent and in almost every society. The Horse Course will cover many unique aspects of equine ownership and touch upon the science behind many of today’s management practices.

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Compétences que vous apprendrez

Disease Management, Nutrition, Animal Behavior, Vital Signs

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4.9 (452 notes)

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AK

Jun 25, 2017

Such a good informative course about Equids. I look at them in a completely different way now, than how I used to see them earlier. All credits to the course and the Professor.

AL

Jun 04, 2016

Excellent course! The course content was informative and the instructor kept the flow going at a nice pace and was interesting to listen to. I highly recommend this course!

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Introduction to The Horse Course

Welcome to Week 1 of The Horse Course! To start off the course, we will begin discussing what exactly an “equid” is. We will cover the many equine species inhabiting our globe. Next, we’ll jump into the history of horses and donkeys, touching upon how they have made such an impact on our own societal development. The second half of week 1 will cover the many breeds of horses and donkeys. We will finish up with a lecture on the equine hybrids.

Welcome to The Horse Course4:11

Introduction to the World’s Equids8:44

Evolution of Horses and Donkeys10:06

Roles of Horses and Donkeys in Human Development8:56

Enseigné par

Chris J. Mortensen, Ph.D.
Professor

Transcription

All right, welcome back.

In this next talk, we're going to talk about the

evolution of horses, and donkeys, and zebras, and the other equids.

So, if we look at evolution, you know, here's the definition, you know,

you're looking at the change in genetics over, over long periods of time.

This is, this is something that happens, you know, naturally, relatively

slowly and as we'll see in, in this lecture over 55

million years is how we can trace, how we can go

back and trace back to the earliest relatives of the horse.

Now we could speed this up a little bit with,

you know, natural, or, excuse me, artificial selection with breeding.

So we do that with modern day breeding.

We can actually speed evolution up.

You know, we can breed for, for better genetics and do this quicker.

Now obviously, you know, the theory of

evolution or natural selection dates back to Darwin.

And the reason I bring this up is because the

horse or the equid is really the model species for evolution.

This is a species that we have more bones that show changes over

time than almost any other species that we've found on Earth to date.

So this is why you now, we always go to the

horse as the model, as we'll see in, in this lecture.

And you know, again we can trace this back, these

changes over time, over 55 million years where Eohippus the very

first horse, you know, looks like a small dog to

where we get actually our tall, even our giraffe breeds today.

Our really tall horses.

And, the two, the two parts of the skeleton

that really we can, we can point to this, is

the dramatic changes in toes, and the lower leg,

changes in the lower leg, and then also their teeth.

You know, as their diets changed over time, their teeth changed with it.

Now here's one of the earlier papers.

There's a whole host of papers that were, you know, the early twentieth

century when you know, Darwin in the

nineteenth century proposed his Theory of Evolution.

Scientists were rushing to find support of evidence.

And this is where they, they really started pointing to the

horse, you know, and can see these, these changes in the bones.

So here is a paper, here is a nice

picture taken by this paper published in 1926 by Mathew.

And you can see that, that the Eocene, you know, as it goes up

to today's modern horse, and it's showing you the skull and the lower legs.

And really, the thing that we're going to notice as this

horse goes from four toes to one toe, to the hoof today.

So looking at that, you know, the eohippus, or Hyracotherium, right

there as you can see, you know, was a four-toed animal.

And then over time, it went to three toes, and then

those toes started to migrate up the leg to one toe.

And you can see that in the bottom picture, so the top

picture is actually a modern horse, or equid, you know, zebra, donkey.

That's what their lower legs look like.

And you'll see the, the splint bones remnant

of the toes that their earlier relatives had.

So we can, you know, see the evidence, direct evidence, in our modern day horses.

Now here's a good graph.

You know?

Obviously, if you go online and Google a lot of this, or search

for a lot of this, you can find different images of horse evolution.

But I always like this one, because it shows the lower leg, and kind of what

the animal would look like over time, or

an artist's guess over time in the phylogenetic tree.

You know, the changes going from, you know, earlier to today.

So we're just going to kind of take some snapshots in here.

You know, we don't have time to go through obviously every, every layer of this.

So we'll start at the beginning and we've already talked about Eohippus

and the other name that it's known as is the Dawn Horse.

And, again, here's what it may look like with

the striped patterns, they're trying to take a guess.

You know, this was more of a browser type animal,

probably ate lots of leaves and small plants and shrubs.

So, they were made for that.

They were made for little forest regions, and, and that's

why their toes and they could climb and do other things.

So, they were relatively short, you know, 20 inches at the shoulder or 50

centimeters and they had four toes on the front, three toes on the back.

And they only had three grinding molars, n'kay.

So like they weren't heavy grazers like our horses today.

So again that's where they think they were

browsers and ate more leaves and small plants.

Now, if we jump, you know, 15 to 20

million years, we can jump and see the mesohippus.

And so, this was roughly, you know, they evolved about 40 million years ago.

And what's unique about this jump is they went from four to three toes.

So, this is where we start seeing evidence of

that, that fourth digit disappearing and going up the leg

on those earlier equids are, well they're really not equids

at this point, the earlier species from eohippus to mesohippus.

And you can see there are not that

much taller, so they're getting a little bit taller,

but what's also interesting about this is they

went from three grinding teeth to six grinding teeth.

So, obviously some, there are some dietary changes driving this evolution, where,

you know, they kind evolve more of a, as they, they evolved

a more grass based diet, their teeth changed with them so they

can handle that eating constant grass, grinding it down and eating it.

So, so from that browse diet to more of a grazing diet.

Now we're going to jump ahead, you know, pretty far again and

this is where we get to dinohippus, which is where we

start seeing evidence of a single-toed horse, you know, they go

on from those three toes to that one toe or one hoof.

So that's where we start to see first evidence.

And this is about 12 million years ago.

So they kind of look like equus which is

the forerunner of today's modern equids and you can

see from this, this image here you can look at the the, the lower leg on this.

And you can still see, you know, just that hoof.

And then those two two toes are just, kind of, remnants.

So maybe a little supportive.

Maybe not.

But really they're, they're getting used to, one toe.

And then, gain, those teeth.

You know?

Here you can see those teeth are starting

to be grinders where they're going to start grinding.

And, you know?

Again as, as their diets changed.

You know?

They, their, their lower legs start to evolve so

that they could get faster and could outrun predators.

And that's what driving this development in this species.

Now we're going to jump ahead to Equus.

So, Equus is actually the, the forerunner for today's donkeys, zebras, and horses.

So, they all trace back to Equus, and so that's where we

get that, that family name and they evolved for about 5 million

years ago and they died out about a million years ago and

these were animals that were found all over the world except Australia.

Okay so the, what's really surprise about this

slide is horses or equus evolved in North America.

So that's where we find a lot, all the bones, all the, all the records are

actually in, in North America and mostly in

the United States, some in Canada, some in Mexico.

So you can see about 55, 58 million years ago that's where Eohippus was evolving and

then 20 million years ago as, as they evolved they spread out North America.

And then roughly they've, they think about 10 million years ago, and

onward, Equus started to migrate, you know, throughout the rest of the world.

So it went over this, this land bridge that's been recognized

between, you know, Siberia and United States of Alaska that's, you

know, not only did early man come over a similar land

bridge but horses actually migrated out, or equus migrated out from there.

And then they spread out throughout Asia

and Europe and then evolved, obviously equus

[UNKNOWN] and equus [UNKNOWN] and then the

zebras also evolved from those early horses.

What is also interesting, about 10,000 years ago, the horses completely

disappeared from North America and, and South America and, and Central America.

You couldn't, you couldn't find them anymore.

And this kind of, you know, coincides with,

with dying out of some other mega [UNKNOWN]

such as, you know, the mammoth and the woolly rhino and some of those others.

So it could have been a change in climate,

you know, with some over hunting, their food could of

been dwindling so there, scientists aren't quite clear on,

on what drove them to extinction, out of the Americas.

But they didn't come back until the fifteenth or

sixteenth century, the 1500s when the Spanish came, and

the conquistadors were you know, venturing through Central, South

and North America, and some horses got away from them.

And that's where they establish the wild populations that we see today.

Now the final slide of this presentation is

that the, the two relatives from horses and this

surprises a lot of people it's, it's pretty

neat and that is the rhinoceros and the tapir.

Those are the horses two closest relatives that we can actually trace

them back to that early ancestor there you can see on the slide.

So, so there are all pretty similar er, with a rhino and a tapir and a horse.

It's, it's, it's pretty, pretty funny and pretty neat.

So one thing you can do, you know, in the United States, there's still some

debate about evolution when, you know, there's a

lot of evidence pointing to evolution being fact.

So if, you know, if you want, you can go in the discussion

board and talk about this further and how horses support the idea of evolution.

I mean, the evidence is there in the soil.

We can see the changes in the bones.

You know I think it would be an interesting

discussion to read and then in the next lecture

we're going to talk about, you know, how horses have

played a role in, in our own evolution and development.

[INAUDIBLE]

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