From Fox to thoroughbred

Seventy million years ago, the horse was only about the size of a fox.A vegetarian,it browsed the plants and low-growing shrubs of swampy prehistoric woodland.But,as the threat from Meat-eating predators grew,and other animals fought for the limited space available, horse found greater safety roaming the plains.Here they had to adapt to the new environment - wide,open spaces and a diet of grass.They developed greater physical strength and the ability to outrun their enemies.At the same time their teeth evolved to graze more efficiently and so complete the horse's "survival kit".

How the horse change

The earliest horse(hyracotherium) lived in swampy woodland and was a small,fox-sizes browser.It had long, slender legs designed for speed. It also had three toes on its back feet and four toes on the front. As the world around it changed,this little creature slowly grew larger,faster and better equipped for grazing dry grasses. Greaual development led first to a sheep-like animal(mesohippus)-with only three toes on its front feet-and then to one about the size of a modern-day Shetland pony(merychippus).From this times on,it is much easier to recognize the features of the modern horse.Further changes,including the development of a solid, single hoof,helped increase its speed and strength(pliohippus) and then completed the evolution into equus - the forerunner of today's horse.

Hyracotherium

About 70-60 million years ago.This early ancestor of today's horse was only the size of a fox.

Mesohippus

About 35-25 million years ago. With longer legs and legs and neck,the 'horse' was now sheep-size.

Merychippus

About 25-10 million years ago. By this stage the horse was pony-size and grazed and grazed on open plains.

Pliohippus

About 7-2 million years ago.This animal was adapted for faster movement.

Equus

Less than 2 million years ago.The foreru-nner of today's horse looked like a native pony breed.

Przewalski's Horse,The only truly wild breed still surviv-ing to the present day,is closely related to the ancestors of domestic horses.

In modern times, it is possible to get the type of pony you want by breeding and crossbreeding. But,long before man was aware of the horse,it was changing and developing:these changes-evolution-enabled the horse to survive.

Growth chart

Thanks to a remarkable complete fossil record of the evolution of the horse, scientists can chart its gradual change into the ancestor of today's native breeds:

Size:The horse became large and stronger.

Legs and feet:These became longer and there was a reduction in the number of toes,with only the middle one surviving.This last toe finally became the horse's hoof.

Back:the back straightened and became much less flexible.

Teeth:The incisor teeth became winder and some premolars developed into proper molars more suitable for grazing.

Head:the front of the skull and lower jaw became deeper to accommodate the increasing height of the cheek teeth.

Brain:The horse's brain gradually in creased in size and became more complicated in its working.