Horse Evolution
The horse is one of the oldest forms of mammal dating
back more than 60 million years ago during the Eocene period. The mammals
of that era, such as, the Eohippus pictured here, did not look much like
the modern day horse. The Eohippus, one of the earliest horse ancestors,
nicknamed the "Dawn horse", was the size of a fox or small to medium sized
dog. Actually its head and body looked more like a deer and it had 5 toes
on each of it's two front feet and three on his two hinds. The toes ended
in a strong, thick, horny type nail and their tips. In the Middle of the
bottom of the foot the toes were supported by a callous like pad.
The Eohippus had little or no lateral vision and it's
teeth were similar to a pig, short and crowned for eating plants. Eohippus
probably stood about 14 inches high at his shoulder and weighed around
12 lbs! Try riding that! LOL.
To date the most outstanding collection of fossils
was found in 1870 by paleontologist O.C.Marsh. With his discoveries a
chain of evolution for the horse had begun. From many of the remains found
throughout history scientists have decided that the Eohippus probably
had a coat similar to a deer in texture and in color right down to fawn
like spots to help to camouflage them. The tail did not have the long
hair as we see today and there was no mane present on these early horse
mammals.
Many discoveries were made of fossils from the horse
evolution chain but some of the most significant were, O.C. Marsh along
with, a nearly perfect specimen found in an Eocene rock formation in 1867,
also discoveries made 30 years earlier in Europe and one excellent find
during an expedition conducted by the California Institute of Technology
paleontologists. This was in 1931 and produced a complete Eohippus skeleton.
It would be a long time before evolution would change
the horse to resemble what we see today and a long time before he would
become a friend, companion of the horse and to use him as a beast of burden
rather than a food source. Unfortunately for horses and horse lovers the
slaughter houses are still brimming with business as there are still places
in the world where horse meat is considered a delicacy. Many cultures
eat horse meat daily and find the animal activists to be unfair in attacking
their way of life. Well, that's another story, so on with this story,
"The Evolution of the Horse".
The horse evolution chain had many long periods of
non-development where all stayed the same. The next significant change
was during the Oligocene period, 35 to 40 million years ago. This era
would see the Mesohippus a much larger version of Eohippus standing 18
to 24 inches at the shoulder come into play in the chain. This guy had
a longer snout looking more like a horses head, much longer legs and neck.
It's back was less arched and it was one of the first three-toed specimens.
The fourth toe turned into a nubbin. This can be seen even on the horses
of today, The callous nub at the back of the leg at the fetlock on todays
horses is what is left of the once fourth toe.
Because this new version of the horse was larger and
with longer limbs would be faster it is believed that the fawn like spots
would probably start to disappear at this point as they would not be needed
as much for camouflage. Scientists think that a plain color or a brown
Mesohippus with spots just on the rump might have been a common sight
during this era.
Now, at the time span of 30 million years ago we find
the Miohippus. On this mammal the ankle joint had begun to change and
this animal had a slight dish, concave, to it's face. He was larger standing
at a minimum of 24 inches at the shoulder and weighing in at much morethan
the Mesohippus. His head was much longer and he had evident incisor teeth.
The evolution evidence shows that the Mesohippus and
the Miohippus co-existed as their species overlapped for more than 4 million
years. Many scientists believe they split off from each other and this
would account for the various fossil remains scattered throughout the
world. These findings indicate as many as three species of Mesohippus
and two species of Miohippus existing at the same time.
Mesohippus finally died out during the mid-Oligocene
era, but the Miohippus continued. It would be another 5 million years
(20 to 25 million years ago) before a significant change in the horse
evolution change would be seen again.
The next horse in the chain, one that looked quite
similar to todays horses, was the Merychippus. This horse stood over 36
inches (ten hands) at the shoulder and although he still had 3 toes there
had been some changes. In the past the weight of the animal was on the
outside toes, by now most of the weight was carried on the inside toe
and the outside toes served little or no purpose. The head changed, the
eye set allowing more area of vision, the neck got longer allowing for
easier grazing.
The Merychippus began to develop defenses and a hightened
sense of smell. The teeth changed to those more like todays horses. These
3 toed grazers were believed to be quick, speedy and surefooted. Several
strains and variations of the Merychippus would develop, each one changing
more to what we would consider the horse we know today. The outside toes
had now began to shrink in size as they were no longer needed and the
foot pad and single toe would begin to develop into what we know as a
horse hoof. The late Miocene, Pliocene and Pleistocene eras would produce
the single hoofed horses that most of us relate to as being our horses
ancestors.
The last significant link in the horse evolution change
before arriving at Equus was Pliohippus. This was the first singled toe,
or hoofed, horse. This Equss prototype was about 12 hands at the shoulder
and had strong leg ligaments to add to his speed and power. This is considered
by many to be the direct descendent to the Equss that would develop about
5 million years later.
Ironically the Pliohippus had a very dished face where
as this was lost when the Equus arose. Another Pliohippus version was
Astrohippus another one toed horse. A third strain also came to be, the
Dinohippus. This horse in the chain was only recently discovered. Some
scientists believe that this version might be the direct desendent to
Equus because he did not have a dished face.
The early Equus had zebra like bodies and short donkeys
like heads. They had tails although short and stiff and straight up manes.
Many of the strains of horses died off for reasons unknown aside from
the obvious but Equus managed to survive and is where we find the basis
for the modern day horse.
Early Horse Groups.
There are many theories on foundation lines but the
most common is the classification listed below.
Pony Type 1 - is thought to have lived in northwest
Europe. This horse was similar to what we know as Exmoors and Icelandic
breeds today and was resistant to wet and cold. They were usually brown
or bay and stood 12-12.2 hands.
Pony Type 2 - was much bigger than type one. It looked
very similar to the Asian Wild horses and was also very resistant to the
cold. It's modern counterpart might be considered to be the Highland Pony.
These guys stood around 14 to 14.2 hands tall. They had a convex profile
and were quite heavy and more stocky than type one. They inhabited northern
Eurasia and due to it's built would have been a better trotter than runner.
They were yellow to dun in color with a dorsal stripe.
Pony Type 3 - was a desert horse living in Central
Asia. He survived the droughts and was resistant to heat. The desert horse
has had a profound influence on the modern day horses offering speed,
stamina and agility. The counterpart of today would be breeds like the
Akhal-Teke. These horses measured 14.3 with long necks and ears, thin
skin, and they were goose-rumped. His body was lsab-sdied and narrow and
he was a bit coarse.
Pony Type 4 - was the protype Arabian standing about
12 hands high. He was not at all coarse like type three, was fine boned
with a straight profile, refined head and a slight concave in the face.
This too was a heat resistant desert horse, with a silky long mane and
tail and fine body hair. It was native to western Asia and was noted for
it's beauty, flat top-line and high tail set.
Modern Horse Groups.
Modern day classifications have become simplified from
years past, now showing three main groups.
A Heavy Horse - is what we would refer to as draft
breeds like the clydesdales, and belgiums. These horses today are used
in all types of disiplines but originally were used more as agriculture
assistants. These breeds are called cold-blooded and usually have deep
chests and short thick legs and broad hooves. They are very strong but
not very fast.
The Pony - as unique porportions. The body length exceeds
it's height at it's withers and it's leg length usually equals it's depth.
A pony stands less than 15 hands tall. Other distinctions in horses is
made based on color, temperment and defining characteristics. Not all
horses fit into these categories some like the cob, polo ponies and hacks
are not classified.
The Light Horse - group is separted into horse and
pony. The separation is determined primarily by size with a horse being
anything 60 inches , 15 hands or taller. Horses are usually porportionate
to their size and leg length whereas a pony is usually stocky in build
and short legged. Horses in this classification have a sloped shoulder
and narrow body. Thoroughbreds, Arabians and other hot blooded horses
generally fall into this category. The exception here would be the "Warmblood"
where does he go, this is usually determined by physical characteristics.
Summary
Above is a reproduced scene of what it might have looked
like on earth during the time of the early horses on the evolutionary
scale. I hope you enjoyed this bit of nostalgia into the past. As more
fossils are found scientists hope to learn more about the interesting
evolution of the horse and someday be able to fill in all the blanks.
Horse evolution is not Straight line, meaning that there are various other
species being found all the time.
Many times a species will split off suddenly from its
ancestors and take on a new form changing and adapting to the envirorment.
This accounts for all types of horses variations like the donkeys, zebras
and others. There is a lot still to be discovered yet about this magnificant
creature the horse and it's ancestory.
By: Pure Illusion Arabians and Crossbreeds
