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cavalli had stripes like zebras until humans broke them in, scientists say

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It was called cavalli had stripes like zebras until humans broke them in, scientists say - Telegraph
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Horses had stripes like zebras until humans broke them in, scientists say
Study reaches black and white conclusion: mankind had a direct impact on horses after domesticating them to run, work or be ridden
Most horses and ponies used to resemble zebras Photo: Alamy
Nature experts have revealed that most horses and ponies resembled zebras with stripes until man changed their colour by taming them.
They lost their "wild" camouflage - pale hair with zebra-like dark stripes, known as the Dun pattern - after they were domesticated by humans.
Researchers said mankind had a direct impact after the first horses were "broken in" to run, work or be ridden.
An international team of scientists has discovered what causes the Dun pattern and why it is lost in most horses.
• Zebras\' stripes \'do not protect them from predators\'
Pale hair colour in Dun horses provides camouflage - horses in the wild are safer from attack by predators like lions and tigers because they are less conspicuous.
In contrast domestic horses - as well as many other domestic animals - have been selected over many generations to be more conspicuous, more appealing or simply different than the wild type.
Most Dun horses have a dark stripe along their back and often show zebra-like leg stripes.
But the majority of domestic horses are non-dun and show a more intense pigmentation that is uniformly distributed.
Horses in the wild are safer from attack by predators like lions
The new study published in Nature Genetics shows non-dun horses carry one of two mutations in a gene called TBX3 that cause the gene to be expressed at lower levels in the skin.
In Dun horses the protein is expressed in the hair bulb - where it blocks pigment production - leading to hairs that are pigmented only on one side of the hair shaft.
This causes the dilute appearance of the Dun horse\'s coat.
By comparing modern horse DNA with that of ancient horses going back over 40,000 years the researchers said one of the non-dun mutations was already present in the latter and was likely selected by humans during domestication.
Unlike the hair of most well-studied mammals, the coloured hairs from Dun horses are not evenly pigmented the whole way around.
Freyja Imsland, a PhD student at Uppsala University in Sweden, said: "The Dun coat color in horses is characterised by pigmentary dilution affecting most of the body hair, leaving areas with undiluted pigment in a variable pattern, with the most common feature being a dark stripe.
"This stripe and other Dun pattern elements are termed primitive markings. Most domestic horses are non-dun, with little or no pigment dilution and a faint or absent dorsal stripe.
"The Dun coat colour is presumed to be wild type, as the Przewalski\'s horse, a close relative of the ancestor of domestic horses, exhibits Dun color, as do other wild horses - the kiang, onager and African wild ass, as well as the quagga, a now extinct sub-species of plains zebra."
• Tigers, camels and zebras to be banned from circuses by 2015, ministers to say
She said the distribution of the Dun coat and the reduced pigment intensity of Dun horses suggest that Dun coloring serves an important camouflage role in horses.
Hairs from the dark areas of Dun horses are in contrast intensely pigmented all around each individual hair, she said.
In spite of scientists having studied hair pigmentation in detail for a very long time, this kind of pigmentation is novel to science, and quite unlike that seen in rodents, primates and carnivores.
Previous studies in humans and laboratory mice show TBX3 controls several critical processes in development that affect bones, breast tissue and the heart.
The study indicates the non-dun variant occurred recently most likely after domestication.
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