Horses are herbivorous ungulate mammals, members of the genus Equus, which first appeared 45 to 55 million years ago, during the Eocene epoch. They began to be domesticated by humans around 4000 BC.
Horses are adapted to running, allowing them to quickly escape predators, and they possess an excellent sense of balance as well as a powerful “fight or flight” mechanism. Related to this need to escape predators in the wild is an unusual trait: horses are able to sleep both standing and lying down, with younger horses tending to sleep much longer than adults. Females, called mares, carry their young for about 11 months, and a young horse, called a foal, can stand and run shortly after birth. Most domestic horses begin training under saddle or harness between the ages of two and four. They reach full adult size by the age of five and have an average lifespan of 25 to 30 years.
Horses are adapted for grazing. An adult horse has 12 incisors at the front of the mouth, adapted for biting grass or other vegetation. At the back of the mouth, there are 24 premolars and molars adapted for chewing.
Horses and humans interact in a wide variety of competitive sports and non-competitive recreational activities, as well as in work activities such as police work, agriculture, entertainment, and therapy. Horses have historically been used in warfare, during which time a wide variety of riding and driving techniques have developed, using many different styles of equipment and methods of control. Many products are derived from horses, including meat, milk, leather, hair, bones, and pharmaceuticals extracted from the urine of pregnant mares. Humans provide domesticated horses with food, water, and shelter, as well as the care of specialists such as veterinarians and farriers.
