Leopard complex spotting and congenital night blindness – ancient horse DNA reveals human breeding preferences

Please notice: caption below press release. Photo: Thomas Hackmann

Over the millennia people have repeatedly changed the coat patterns and colours of domestic animals through selective breeding. In particular, leopard complex spotting in horses has been repeatedly a favourite pattern since the beginning of domestication about 5500 years ago, as an international team of scientists has now been able to demonstrate. The study emphasises how changing fashions and repeated cross-breeding of wild and domestic horses have substantially enhanced the genetic diversity of the domestic horse. The results of the study have just been published in the renowned scientific journal Philosophical Transactions B of the Royal Society.

White coat with black spots: almost every child knows “Lilla Gubben”, the horse of Pippi Longstocking. How popular were such spotted and speckled horses (displaying the so called “leopard complex spotting”) during the last millennia? As researchers have now discovered, the occurrence of these horses fluctuated considerably during the course of history.

Under the leadership of scientists from the German Leibniz Institute for Zoo and Wildlife Research (IZW), an international team of researchers reconstructed the appearance (phenotype) of 96 horses from archaeological bones and teeth originating from the late Pleistocene to medieval times by identifying the specific variant of the genes responsible for coat patterns in each individual. Although a considerable number of domestic horses from the early Bronze Age (2700 – 2000 B.C.) have been genetically identified with leopard complex spotting, this coat colour seems to have almost disappeared at the end of this period. One reason might be that homozygous animals (e.g. Appaloosa and American Miniature Horse) do not only show the white coat colour but are also night-blind. The ability to see is of great importance for communication, orientation, searching for food and for avoiding predators. Therefore, night-blind animals have only a small chance to survive in the wild. In human care, night-blind horses are described as nervous and timid and difficult to handle at dusk and during darkness.

About 1000 to 1500 years later, leopard complex spotting was again on the increase. The coat colour was reintroduced into the domestic gene pool from cross-breeding with numerous wild animals. Different preferences of horse breeders over the course of millennia emphasise the importance of genetic diversity of domestic animals. Today, when the original wild form of horse and cattle are long extinct and backcrossing is hence impossible, modern animal breeding continues to be driven towards a loss of genetic diversity. Such a decline in genetic variability enormously restricts options for future changes in breeding aims and makes breeders dependent on only a few high-performance breeds.

After the Iron Age a renewed upswing in horses with leopard complex spotting was reported. “The behaviour of breeders and their preferences changed at that time as it does today” says Arne Ludwig from the IZW, the leader of the study. Changing interests in horses with leopard complex spotting can also be recognised during medieval times, when paintings and text samples demonstrate that they enjoyed a high reputation as. They belonged to the favourite animals of the nobles and were a symbol of chastity. During the baroque period they were also favoured but then went out of fashion. Today spotted coat patterns occur in many breeds and breeders show an increasing interest in recent years.

”The idea of disruptive, alternative selection explains how genetic diversity in domestic populations could be preserved despite relevant selection for or against a certain trait. The problem in breeding nowadays is that we cannot go back to the appropriate wildlife species, because they have been simply eradicated or the wild types have vanished by selection. The gene pool of today’s domestic animal breeds will be negatively affected by this development. The missing genetic diversity severely restricts the possibilities of breeding in the future“, comments Ludwig.



Examples of leopard complex horses in human artefacts and culture. Pictures from left to right: (a) the panel of the dappled horses—‘Le panneau des Chevaux ponctués’, Cabrerets, Lot, France (Photo from P. Cabrol, Centre de Préhistoire du Pech Merle). (b) There are several examples of spotted horses in the art of ancient Egypt dating from 1500 to 1300 BC (http://www.spanishjennet.org/history.shtml). (c) The mosaics from North Africa are from the Dominus Iulius at Carthage [1]. (d) This Persian plateau was passed from conqueror to conqueror until the arrival of the Muslims from the south in 640 AD. Persian art objects from that time to the present show spotted horses, suggesting that spotted horses were common in Persia since before the Muslim conquest (picture from http://www.spanishjennet.org/history.shtml). (e) Chinese horse sculptures dating to 600–900 AD. (f) The mosaic (Spain 975 AD) is from the Beato de Gerona Codex, dating to 975 and attributed to the Abad Domenicus [2]. (g) The famous eighteenth century painting from John Wootton titled ‘Lady Conaway's Spanish Jennet’ is owned by the Marquees of Hertford. (h) Modern Knabstrupper horse from the famous horse breeding farm ‘Aus der schützenden Hand’ (Werpeloh, Germany) showing leopard complex spotting (Photo: Thomas Hackmann).

Ludwig A, Reissmann M, Benecke N, Bellone R, Sandoval-Castellanos E, Cieslak M, Fortes GG, Morales-Muñiz A, Hofreiter M, Pruvost M (2014): Twenty-five thousand years fluctuating selection on leopard complex spotting and congenital night blindness in horses. PHIL TRANS R SOC B 370, 20130386. doi:
Leibniz Institute for Zoo and Wildlife Research (IZW)
in the Forschungsverbund Berlin e.V.
Alfred-Kowalke-Str. 17
10315 Berlin
For press questions:
Steven Seet, +49 30 5168 125, seet@izw-berlin.de
For scientific questions:
PD Dr. Arne Ludwig, +49 30 5168 206, ludwig@izw-berlin.de


Background information:

The Leibniz Institute for Zoo and Wildlife Research (IZW) investigates the vitality and adaptability of wildlife populations in mammalian and avian species of outstanding ecological interest that face anthropogenic challenges. It studies the adaptive value of traits in the life cycle of wildlife, wildlife diseases and clarifies the biological basis and development of methods for the protection of threatened species. Such knowledge is a precondition for a scientifically based approach to conservation and for the development of concepts for the ecologically sustainable use of natural resources. The IZW belongs to the Forschungsverbund Berlin e.V. (www.fv-berlin.de)



The Leibniz Association connects 89 independent research institutions that range in focus from the natural, engineering and environmental sciences via economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance. They conduct knowledge-driven and applied basic research, maintain scientific infrastructure and provide research-based services. The Leibniz Association identifies focus areas for knowledge transfer to policy-makers, academia, business and the public. Leibniz Institutes collaborate intensively with universities – in the form of “WissenschaftsCampi” (thematic partnerships between university and non-university research institutes), for example – as well as with industry and other partners at home and abroad. They are subject to an independent evaluation procedure that is unparalleled in its transparency. Due to the institutes’ importance for the country as a whole, they are funded jointly by the Federation and the Länder, employing some 17,500 individuals, including 8,800 researchers. The entire budget of all the institutes is approximately 1.5 billion EUR.


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