Anything Equine,  Equestrian topic

A Little Equine Evolution

Drawing of Hagerman horse (left) with Grevy's zebra (middle) and Domesticated horse (right)
Drawing of Hagerman horse (left) with Grevy’s zebra (middle) and Domesticated horse (right)

Modest in stature, Equus moved over great distances. [Fossils of Equus collected in the Hagerman horse quarries in Idaho – on left of illustration]

In stark contrast to his much smaller predecessor now known as Orohippus (pad footed, 4 toes in front, 3 toes behind, and approximately 10”-20” at the shoulder, small forest animal with a flexible back, a short neck, short legs, and a smallish nose, teeth of an omnivore, however over twenty million years, began to evolve into plant eaters, of the Eocene Epoch 40-50 million years ago), these beasts traveled on singular hooves.

Their spines were more rigid and their necks were longer. They had relatively long legs, and a head that would be recognized as ‘horse’; a long nose and a bigger jaw that allowed for more grinding type teeth, specialized in grazing and browsing. On average, they were, on average, 13 hands tall.

These primitive ancestors of the horse existed over three million years ago during Pliocene Epoch (Pliocene Epoch extends approximately 5.3 million years ago to approximately 2.58 million years ago).

Genus Equus had stocky, thick bodies (Neilson), and what we might know now as the ‘dun factor’; with some striping on their legs and backs. They were highly adaptable, and as they increased in numbers they developed into over a dozen species. They thrived in diverse habitats, and migrated great distances. The route of these prehistorical horses “led from America through Siberia and Central Asia to Africa and Eastern Europe, where evidence of the earliest domestication of horses was found”. [Population genetic parameters of aboriginal Yakut horses as related to modern breeds of the domestic horse Equus caballus L. by Tikhonov, Cothran, and Kniazev. Published in Genetika. 1998 Jun;34(6):796-809.] This occurred during the major glaciations of the late Pliocene and early Pleistocene Epochs.

Time elapsed, measured by hundreds of thousands of years. They evolved into zebras, onagers, donkeys and horses. There were Equus species amassing globally, running in enormous herds, each being honed and shaped by the specific ecological pressures and opportunities.

Fossils have been found all over the world with the exception of Antarctica and Australia. These horses became extinct in North and South America during the late Pleistocene Epoch [The Pleistocene Epoch extends from approximately 2.58 million years ago to approximately 10-12,000 years before present. Extinction event occurred about 10,000 years ago during the last Ice Age.], but they survived in Europe and Asia.

There, major differences in nutrition, seasonal climate conditions, shade, sun, rock and sand shaped our Equus into diverse and capable species. Forest, mountains, plains. Lush, arid, harsh. It didn’t matter. They migrated and adapted magnificently.

It is possible, that the ‘types’ of horses that would have benefited the most by tweaking the gene for heart size, and for the perfection of the breathing apparatus, would have been those living in steppes and the desert areas. Their survival would have depended upon their ability to run farther and faster than their predators.[Primarily of the ‘cat’ family, including (especially) lions.] Environmental pressure was ever present; the requirement for a bigger, better machine to pump blood, and exchange more air. The cellular part of respiration also had to develop an appropriate, complimentary metabolism.

During metabolism, fats, proteins and sugars are broken down (in a series of chemical reactions) from forage, in order to release energy. In turn, that energy is used to perform physical functions such as physical activity, growth, and to build and rebuild their cellular components. In other words, run fast and long, never tire, and recover very quickly.

Types of horses that evolved in wooded areas, specifically the Forest Horse and the Draft subspecies may have had to dart quickly to find a suitable hiding place, perhaps not taxing their cardio-vascular and respiratory systems in the way the steppe and desert animals would have. Natural selection may have favored the larger nasal cavity, which is conducive to the needs of sudden exertion. A generous nasal cavity would allow for the sustainability of short, powerful bursts of speed. This may have resulted in the convex profile we see in many draft breeds today. If they had the genetic code for the larger heart system, lack of selection pressure may have seen the trait decline in those ‘types’.

Dr. Gus Cothran, a geneticist with a formidable background, did extensive DNA testing on many breeds both in the United States, Europe, South America and Iran. His results placed the Przewalski horse as the most ancient breed following our pre-historic Equus species, with the Caspian horse [pony] next, and the Yabou and Turkoman strains following in that order. (Firouz)

Once on the Central Asian steppes, the little horse grew in numbers, and some parted ways. The environmental conditions continued to shape them, and within various climates, they adapted. They either mastered the challenges or perished.

“In this sense the built-in capacity for species evolution is not based on the individual but rather living systems that are interlinked within a coherent whole: Living systems are thus neither the subjects alone, nor objects isolated, but both subjects and objects in a mutually communicating universe of meaning”.

~Ho and Popp, “Gaia and the Evolution of Coherence.”

Millions of years made the horse, and not one thing was neglected, for the Spirit, wind, stamina, heart, and coloring were all perfected.

And then there was man.

Go Back to Chapter One: Legendary Hearts

Go Back to Chapter Two: The Godolphin Horse and the Byerley Turk

Chapter Three (going back in time): A Little Equine Evolution

Continue to Chapter Four (going forward in time): Central Asian Horses

Chapter Five (going full circle): The Spanish Horses

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