The Origins of Horses
The earliest ancestor of the modern horse, called Eohippus, lived about 60 million years ago on grasslands in both North America and Europe. This small animal foraged shrubs and low lying leaves for food. Eohippus had five toes on its forelimbs and hind limbs. Four of these toes on the forelimbs and three on the hind limbs had small hooves. The fifth toe on the forelimb, and first and fifth toes on the hind limbs did not touch the ground. When climatic changes resulted in changes to the plants they depended on for food, the teeth of the Dohippus evolved to handle different types of plants.
The next ancestor of the modern horse found was Mesohippus, who lived approximately 30 million years ago. Mesohippus was slightly taller and had a longer neck and teeth suitable for grazing grasses and brush. Mesohippus had three toes on each foot and a narrow skull, characteristic of modern horses.
Mesohippus evolved into Parahippus during a time of expanding plains and grasses about 23 million years ago. Parahippus had longer legs and teeth adapted to chewing and grinding grass.
About 15 million years ago, Merychippus, the first animal recognizable as a horse, evolved. These early horses were adapted to running by carrying their weight mainly on their middle toes. As this animal continued to evolve, the other two toes disappeared.
About 4 million years ago, Equus evolved with elongated legs and a densely packed foot suited for running in open grasslands and molars suitable for grazing.
According to biologist Jared Diamond, an animal species is domesticated if it meets six criteria:
- Has a flexible diet (not too difficult to provide)
- Matures reasonably quickly
- Breeds in captivity
- Has a pleasant disposition
- Is unlikely to panic
- Has a modifiable, or changeable, social hierarchy so that they can recognize a human as its leader.
There is a difference between a tame animal and a domesticated animal. Giraffes, wolves and bears have been tamed, but are not domesticated. One important measure of domestication is whether an animal born to wild parents would differ in behaviour from one born to domesticated parents.
These early horses were primarily viewed as a source of food by humans, resulting in the first steps towards domestication. Horses were kept, not only as a food source, but also for tasks suited to their strength and speed. Until recently, there have been disagreements over where and when horses were domesticated. However, research suggests that domestication first occurred approximately 6,000 years ago.
Equus caballus is considered to be the ancestor of the modern horse and exists today in hundreds of different breeds. Many of these breeds have resulted from selective breeding as horses became domesticated. Humans have bred horses to perform specific tasks, including driving, jumping or racing. Adaptation to different environments has also influenced the development of different breed characteristics, such as thicker coats in cold climates or tougher hooves in rocky terrain.
As humans changed from hunters and gatherers to farmers, they started to develop animal husbandry practices.