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Grey Horses linked to 'Fast Aging' DNA
Scientists have discovered DNA causes fast ageing in horses
Grey horses, such as racing’s Desert Orchid or the famous Showjumper Milton, are actually mutants whose defective DNA carries a gene that accelerates ageing and rapidly turns their coats grey, scientist have discovered.
Desert Orchid ........................................Milton
Such horses would probably never have survived in the wild but for one particular grey horse, born thousands of years ago, which so caught the eye of ancient humans that they protected it and did their best to breed more, according to a new study.
They were so successful that the same horse became the ancestor of almost all grey horses born since. It means that Milton and Desert Orchid were probably related.
The key finding of the researchers, at Uppsala University in Sweden, is that almost all grey horses seem to carry an identical gene, implying that it originated in a single common ancestor.
Grey horses are unlikely to have survived in the wild. The white colouring makes them easy prey for predators, while the gene sharply raises the risk of such horses getting skin cancer. This implies that humans probably intervened to make sure they flourished.
“It is a fascinating thought that once upon a time a horse was born that turned grey and then white and the people that observed it were so fascinated that they used the horse for breeding so that the mutation could be transmitted from generation to generation,” said Leif Anderson, who led the study.
Today about one horse in 10 carries the mutation, dubbed the “greying with age” gene. Such horses are brown, chestnut or black when they are born but their coats turn white within about six years.
They are distinct, however, from the rarer albino horses, which are white at birth.
Although born a solid colour, both these foals are carrying the 'greying' gene and will turn grey/white as they get older.
Samantha Brooks, a geneticist and equine expert at Cornell University, New York, said the mutation in the “greying with age” gene meant that the pigment cells – or melanocytes – in the hair follicles in effect “dried up” early in life. The hairs keep growing but without any pigment they become white.
The absence of the pigment means the skin is less protected from sunlight and so is at greater risk of skin cancers.
“About 75% of grey horses aged over 15 years have a benign form of melanoma that may develop into a malignant melanoma,” said Anderson.
The discovery could shed light on ageing and cancer development in humans, too. Grey horses appear to be going through an ultra fast version of what happens in people.
Historians believe wild horses were first tamed by humans about 10,000 years ago on the steppes of central Asia. It was probably there that the first grey horse was born. Since then, grey horses have become associated with legend and kingship. Pegasus, the winged horse of Greek myth, is usually depicted as a grey.
King Arthur is said to have ridden a grey horse, as is William the Conqueror at the battle of Hastings in 1066.
“They have this mythical image of purity and sanctity about them,” said Brooks. “They have this innocent trait about them.”