Why white horses are white

This video from Britain is called The White Horses TV Series start sequence.

From Uppsala University in Sweden:

The genetics of the white horse unraveled

The white horse is an icon for dignity which has had a huge impact on human culture across the world. An international team led by researchers at Uppsala University has now identified the mutation causing this spectacular trait and show that white horses carry an identical mutation that can be traced back to a common ancestor that lived thousands of years ago. The study is interesting for medical research since this mutation also enhance the risk for melanoma. The paper is published on July 20 on the website of Nature Genetics.

The great majority of white horses carry the dominant mutation Greying with age. A Grey horse is born coloured (black, brown or chestnut) but the greying process starts already during its first year and they are normally completely white by six to eight years of age but the skin remains pigmented. Thus, the process resembles greying in humans but the process is ultrafast in these horses. The research presented now demonstrates that all Grey horses carry exactly the same mutation which must have been inherited from a common ancestor that lived thousands of years ago.

– It is a fascinating thought that once upon a time a horse was born that turned grey and subsequently white and the people that observed it were so fascinated by its spectacular appearance that they used the horse for breeding so that the mutation could be transmitted from generation to generation, says Leif Andersson who led the study. Today about one horse in ten carries the mutation for Greying with age.

King Charles XI of Sweden at the Battle of Lund in 1676. Painting by David Klöcker Ehrenstrahl in 1682It is obvious that humans across the world have greatly valued these white horses as documented by the rich collection of stories and paintings featuring white horses. In the paper the white horse as an icon for dignity is illustrated by reproducing a painting from the late 17th century of the Swedish king Karl XI on his white horse Brilliant.

The Grey horse is also very interesting from a medical point of view since the mutation also predisposes for development of melanoma. About 75% of Grey horses older than 15 years of age have a benign form of melanoma that in some cases develops into a malignant melanoma. Thus, the study reported today has also given new insight in a molecular pathway that may lead to tumour development.

We propose that the Grey mutation stimulates growth of melanocytes and that this leads to a premature loss of the melanocyte stem cells needed for hair pigmentation whereas the mutation promotes an expansion of some of the melanocytes causing skin pigmentation, says Leif Andersson.

Domestic animals constitute extraordinary models for evolution of biological diversity as already recognized by Charles Darwin. The white horse is a beautiful illustration of the importance of regulatory mutations as a major underlying mechanism for phenotypic diversity within and between species. The Grey mutation does not change any protein structure but it affects the genetic regulation of two genes. The researchers found that the white horses carry an extra copy of a DNA segment located in one of these genes.

It is very likely that regulatory mutations like the one we found in these white horses constitute the dominating class of mutations explaining differences between breeds of domestic animals as well as between species like humans and chimpanzee, concludes Leif Andersson.


For more information contact: Professor Leif Andersson, Department of Medical biochemistry and microbiology, Uppsala University, phone: +46 (0)18 471 4904, +46 (0)70-514 4904, e-mail: leif.andersson@imbim.uu.se

Unusually coloured African animals: here.

Horses Domesticated 9,000 Years Ago in Saudi Arabia: here.

Remains of horses and chariots unearthed from tomb dating back to 3,000-year-old Chinese dynasty: here.

3 thoughts on “Why white horses are white

  1. Horses first ridden – and milked – 5,500 years ago

    Thu Mar 5, 2009 2:27pm EST

    By Ben Hirschler

    LONDON (Reuters) – Horses were first domesticated on the plains of northern Kazakhstan some 5,500 years ago — 1,000 years earlier than thought — by people who rode them and drank their milk, researchers said on Thursday.

    Taming horses changed human history, influencing everything from transport to agriculture to warfare. But experts have struggled to pinpoint when and where it first happened.

    Now archaeologists think they have the answer, after finding the world’s oldest horse farm among the Kazakh people of the ancient Botai culture.

    Remains of bones, teeth and shards of pottery, used to store mare’s milk, all indicate horses were selectively bred and exploited for domestic use east of the Ural mountains around 2,000 years before they are known to have been used in Europe.

    Alan Outram from Britain’s University of Exeter said the new findings, published in the journal Science, changed understanding of how early societies developed.

    “Once you have horse riding you’ve got much greater transport and trade capability, as well as potential advantages in warfare,” he said in a telephone interview.

    “If it was happening this early, then you’ve got to think about those forces for social and economic change happening earlier too — and it is possible that there are yet earlier sites we haven’t found.”

    Archaeologists have suspected for some time that the Botai people were the world’s first horsemen but previous sketchy evidence has been disputed, with some arguing that the Botai simply hunted horses.

    Now Outram and colleagues believe they have three conclusive pieces of evidence proving domestication.

    They found that the leg bones of ancient Botai horses were similar to later Bronze Age domestic horses and very different from wild ones, suggesting breeding by humans.

    They also identified clear markings on the horses’ teeth, indicating they wore bits or bridles, and finally an analysis of organic residues in broken pots found traces of horse milk.

    Mare’s milk, usually fermented into a slightly alcoholic drink called “koumiss,” is still drunk in Kazakhstan.

    (Editing by Mark Trevelyan)


  2. Pingback: What horses’ ears and eyes say, new research | Dear Kitty. Some blog

  3. Pingback: Zebras, why their stripes? | Dear Kitty. Some blog

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