Dawn of the horse



This artist's impression depicts the dawn horse or Hyracotherium, considered by palaeontologists to be the earliest horse. Petite by today's standards, the animal stood only 20 to 35 centimetres tall at the shoulder and had four hoofed toes on the front feet and three on the back. This early horse lived about 55 million years ago during the Eocene. It inhabited both North America and Europe.



(Image: Christian Darkin/Science Photo Library)

The last wild horses



Przewalski's horse (Equus ferus przewalskii) is the last truly wild horse. Once extinct in the wild, these tan ponies are again grazing the steppes of their native Mongolia thanks to an intensive captive breeding programme. However, they are still considered critically endangered.



Przewalski's horse carries two chromosomes more than its domesticated relatives. Its range once extended from China to Germany before hunting and intermixing with domesticated horses reduced its numbers. Here a Przewalski's horse jumps near a wisent, or European bison, at a wildlife reserve outside Berlin, Germany.



(Image: Michael Urban/AFP/Getty) Advertisement

Feral transplants seek native status



They may be the descendants of domesticated European horses, but the mustangs of the American West could soon be classified as a native species if a federal case succeeds. Samples recovered from native horse fossils in the US are genetically indistinguishable from today's wild horses – but the question remains as to whether thousands of years of domestication in Europe voids the previous 1.4 million years of evolution in the US.



In this photo from the Pryor Mountain Wild Horse Range in Montana, a young black stallion challenges another stud.



(Image: Yva Momatiuk/John Eastcott/Minden/Getty)

Breeding a master racehorse



The modern thoroughbred racehorse was developed in the 18th century by crossing a trio of outstanding Middle Eastern horses with British mares. The grandaddy of all thoroughbreds seems to be a stallion, Darley Arabian, bought in Syria in 1704 and shipped back to Britain. Darley Arabian is shown here in a painting by John Wootton. Nearly 95 per cent of today's thoroughbred horses could trace their Y chromosomes back to this stud.



(Image: Painting by John Wootton)

Mini horses push breeding limits



Human selection has shaped horses into a variety of forms from the beefy Clydesdale to the diminutive miniature horse. Tiny Bella Contessa stands just 53 centimetres tall at the shoulder in this photograph from last October. She is a contender for the world's smallest horse. Miniature horses maintain the physical attributes of a horse despite their small stature.



(Image: BMUSA/Getty)