Horse Evolution – Stuff You Want To Know
The horse as it is known today adapted by evolution to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not.
Horses and other equids are odd-toed ungulates of the order Perissodactyla, a relatively ancient group of browsing and grazing animals that first arose less than 10 million years after the dinosaurs became extinct. In the past, this order contained twelve families, but only three families— Equidae (the horse and related species), the tapir and the rhinoceros—have survived to the present day.
The earliest equids known as Hyracotherium developed approximately 54 million years ago, during the Eocene period. One of the first true horse species, it had 4 toes on each front foot, and 3 toes on each back foot. the extra toe on the front feet soon disappeared, and by the Pleistocene era, as the horse adapted to a drier, prairie environment, the 2nd and 4th toes disappeared on all feet, and horses became bigger. These side toes first shrunk in size until they have vanished in modern horses. All that remains are a set of small vestigial bones on either side of the cannon (metacarpal or metatarsal) bone, known informally as splint bones, which are a frequent source of splints, a common injury in the modern horse. Their legs also lengthened as their toes disappeared and until they were a hoofed animal capable of running at great speed.
Over millions of years, equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, and grazing of tougher plains grasses. Thus the proto-horses changed from leaf-eating forest-dwellers to grass-eating inhabitants of semi-arid regions worldwide, including the steppes of Eurasia and the Great Plains of North America. For reasons not fully understood, Equus caballus disappeared from North America around 10,000 years ago, at the end of the last Ice Age.
Competing theories exist as to the time and place of initial domestication. The earliest evidence for the domestication of the horse comes from Central Asia and dates to approximately 4,500 BC. Archaeological finds such as the Sintashta chariot burials provided unequivocal evidence that the horse was definitely domesticated by 2000 BC.
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December 20th, 2009 at 5:02 pm
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