The most puzzling question concerning the life appearance of the European wild horse is the mane. For a pretty long time, the falling mane of the domestic horse has been considered a result of domestication, as all extant wild equines have an erect mane. In domestic donkeys, domestication also resulted in a falling mane in some breeds (see here, for example).
It has been claimed in recent years that European wild horses or the wild progenitors of the domestic horse might indeed have had a falling mane. The falling mane allegedly helps to divert rain from neck and face in a more humid environment, and indeed all extant wild equines are found in arid ecosystems. However, it has to be kept in mind that the horse was domesticated in the arid steppe, therefore this is not a compelling argument for the western wild horse having a falling mane. Another argument is that an Equus lambei carcass found in North America allegedly shows a falling mane (I have been unable to find quality photos of the carcass, unfortunately). It has to be kept in mind though that Equus lambei, the North American form, is probably more distantly related to the domestic horse than Przewalski's horses, or Siberian Pleistocene horses, which have/had short erect manes of about 15 cm length [2]. Therefore, the falling mane would have to have evolved at least two times in wild equines and such a mane cannot be inferred by phylogenetic bracketing for European/western wild horses.
Then there are the manifold Pleistocene cave paintings which all show horses with an erect mane very clearly (see here and here, for example). Since many of the depicted horses show a strong resemblance to the Przewalski's horse, it has been assumed that the horses present in Europe during the late Pleistocene must have been of the przewalskii lineage. However, it has been found that a horse remain from Belgium from approximately 36.000 years ago is genetically closer to Iberian wild horses and domestic horses than to Przewalski's horses [3]. It is thus assumed that these short-maned horses are the ancestors of European wild horses (which the authors of Fages et al. call "tarpans") [3]. Interestingly, Siberian Pleistocene wild horses (referred to as Equus lenensis), which were short-maned to according to a carcass [2], are actually closer to domestic horses than Holocene Iberian wild horses. And the Przewalski's horse, which has an upright mane as well, is closer to the domestic horse than both the Holocene Iberian and Pleistocene Siberian wild horse according to Fages et al. [3].
Therefore, it seems highly likely that at least Holocene Iberian wild horses had an upright mane, and probably the (other) ancestors of domestic horses in the Eurasian steppe as well.
Literature:
[1] Sandoval-Castellanos et al.: Coat colour adaption of post-glacial horses to increasing forest vegetation. 2017
[2] Lazarev, P.: Large mammals of the Anthropogene of Yakutia. 2005.
[3] Fages et al.: Tracking five millennia of horse managment with extensive ancient genome time series. 2019.
It seems that Przewalski and european horses separated something like 35000 years ago. Why use dedomesticated horses instead of Przewalski in europe ?
ReplyDeletehttps://link.springer.com/article/10.1007/s10914-020-09517-6
Availability and preservation of non-steppic ecotypes
DeleteI read that "Ice Age" horse pictures have been found in Colombia in South America. See https://www.theguardian.com/science/2020/nov/29/sistine-chapel-of-the-ancients-rock-art-discovered-in-remote-amazon-forest
ReplyDeleteHas anyone seen these images? Is it clear if the manes are upright or falling?
I have. The manes look short but it is unclear if they are stiff or falling. They don't really show the animal's natural colour either. However we do now know that American Equus were likely conspecific with Equus ferus, and should probably be designated E. f. neogaeus.
DeleteThanks Rhys. Are the images online or available any other way? Dominic
DeleteI would expect that short upright manes would be an advantage in hot / dry climates and falling manes in cold / wet climates, and that selection pressure either way could be quite strong if the climate changed. Exmoors tend to have dense manes but not the long manes found in eg Fell ponies.
ReplyDeleteNone of the british pony breeds ccommonly have dorsal stripes apart from Connemaras & Highlands, both areas on the far north & west of the British Isles, with strong cultural links and possibly Nordic settlement history.
I always wandered how the mane could be connected with the climate, as steps are very hot in summer and very cold in winter, and it does not seem that mane changes length seasonally. Przewalsky horses do changes fur density seasonally, and a bit fur length too,their fur is well adapted to harsh climate but their mane is erected all year long. I suppose, but it is just a personal guess, that maybe mane had others functions, as protection against bites of other horser and ,in some ways,predators. An erected mane fills the mouth, is bothersome, and let the bite not reach the neck easily. I also think that long, falling mane is a domestic feature, as people see it like human hair and it facilitates the distinction between domestic and wild
DeleteThis isn't necessarily a statement in favour of falling manes, but its worth noting that the trait would only have to have evolved once, as there was substantial hybridization between all lineages. If beneficial, it could easily have spread. There might also be some epigenetic effects.
ReplyDelete