The way of a horse's going is the truth of him.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

\

 

 

 

 

 

 




 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Prehistory

Some individuals in any species are better suited than others to survive changes and pressures in the environment. That means that those individuals will survive and live long enough to reproduce, passing their favorable characteristics on to their offspring, making them in turn better suited to survive and reproduce.   This is called natural selection.  It is how characteristics are passed from generation to generation.  The mechanisms that determine the structure of the individual, the genes, often have several mutations when cells divide but most are meaningless and have no affect.  Some mutations are disastrous, such as when a cell turns cancerous.  Others result in a characteristic that makes the individual superior to its competitors for surviving some factor of its environment.  But the only time these new characteristics are really significant, is when they take place in the gametes (ova and sperm).  Only then can the change be passed on.

Humans can have a great impact on selection.  We select breeding stock for specific desired characteristics then breed to perpetuate it, to "fix" the characteristic in the breed.  An example of this type of selection is the way Arabian horses have changed since they were first imported into America.  Look at pictures of the first imports, then look at what is being shown in the show rings today.  Hardly the same horse. There is no value judgment here - simply an observation.

The following example highlights the evolution of just one line of horses, the one that evolved into Equus, the modern horse.  In reality, equine evolution resembles a tree, not a straight line.  There are many branches along the way and not all survived.  Click the tree to see my poor attempts at constructing a graphic representation of how the fossils fall (so to speak).

Hyracotherium, or Eohippus (the dawn horse), dating more than 60 million years ago during the Eocene, stood 14 inches tall, had 5 toes on front, 3 toes on hind. Fawn-like spots. Teeth pig-like. It fed on leaves as it roamed over boggy ground. Small size and multi-toed feet kept it from sinking into the swamp. The remains have been found in Utah and Wyoming.

Mesohippus. Oligocene period, 35 to 40 million years ago. 18-24 inches tall. Toes 3 and 3.  4th toe turned into the Ergot. Spots disappearing except over the rump.

Miohippus. 30 million years ago. 24 inches tall.  First incisors. Fetlock joints changing. Slight dish to face.

As many as three species of Mesohippus and two species of Miohippus existed at the same time overlapping 40 million years.  Mesohippus finally died out during the mid-Oligocene era, but the Miohippus continued.

Merychippus. 20-25 million years ago. 36 inches. Toes still 3 and 3, but weight shifting to middle toe. Teeth now similar to modern horse. Neck longer.

Pliohippus. 12 hands tall (48 inches). Single toed.  3 species: Pliohippus, Astrohippus, and Dinohippus (a recent discovery). Pliohippus had an extreme dish whereas Dinohippus did not. It may prove to be that it was Dinohippus that evolved into Equus and not Pliohippus as has always been thought.  Early Equus did not have a dished face.

Equus, early horse families. The most common classifications are:

Pony Type 1. 12-12.2 hands tall. Northwest Europe. Similar to Exmoors and Icelandic breeds today. Resistant to wet and cold. Usually brown or bay.

Pony Type 2. 14 to 14.2 hands tall. Bigger than Pony Type 1. Similar to Asian Wild horses, resistant to cold. Convex profile, stocky. Inhabited northern Eurasia. Yellow to dun in color with a dorsal stripe.

Pony Type 3. 14.3 hands tall. Desert horse living in Central Asia. Drought and heat resistant. Long necks, thin skin, goose-rumped.

Pony Type 4. 12 hands tall. Prototype Arabian. Fine boned, straight profile, refined head with a slight dish. Heat resistant desert horse. Silky long mane and tail, fine body hair. Native to western Asia.

 

                                           [Home] [Stallion]  [Mares]  [Foals]  [Sales]  [Ancestors]  [Memory]  [Articles]  [Family]  [Friends]  [Library]  [Links]