The gene machine: The vanishing dun coloring of domesticated horses

Once a prevalent characteristic in horses, long-term breeding and domestication have very nearly lost the dun color from the equine gene pool. The pale hair coat and remarkable zebra stripes were adapted as a camouflage tactic throughout evolution that has long since been physically utilized except in the small population of remaining wild horses.
A new study by Nature Genetics has shed some light on the remaining beautiful dun color in our equine population.
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Natural selection in older times had attributed to the more inconspicuous color coats of early horses, including light bays, grays, and duns, all neutral shades to allow horses to better blend in with their surroundings and go unnoticed by predators.
Contrary to natural selection, when controlled breeding came on to the scene, humans tended to favor the brighter, more vibrant coats that were once a red target for these prey animals.
“Dun is clearly one of the most interesting coat color variants in domestic animals because it does not just change the color but the color pattern,” stated Leif Andersson in an article on phys.org.
He refers to the unique zebra pattern around the legs and the black stripe down their back. The otherwise pale hair coat indicates an unusual pigment dilution. Analysts have determined this is due to a single gene that codes for the TBX3 transcription factor. They identified two definite color variations they call ‘dun’ and ‘nondun1', and through research have shown how domestication is phasing out the ‘dun’ variation in the genome pool.
Additional studies will have to be performed to further analyze the remaining abundance of the variations, but for now, as horse lovers, we should appreciate the wild beauty of the dun horses that remain.
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Resources phys.org

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