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How the Horse Evolved
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 prototype 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 disciplines 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, temperament 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 separated 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
proportionate 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.
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