Przewalski horse

The Przewalski horse (Equus caballus przewalskii) is the closest relative to the modern horse (Equus caballus caballus). In contrast to Mustangs, which are feral domestic horses (Equus caballus caballus), the Przewalski horse is the only true "wild" horse that is alive today, although severely endangered to go extinct. Only 2000 Przewalski horses are alive today. The natural habitat of Przewalski horses are the steppes of much of Eurasia.

People often assumed that the Przewalksi horse is closely related to the domestic horse, having split from each other around the time of domestication of the modern horse, around 6,000-10,000 years ago. However, as my colleague at Penn State discovered, based on sequencing the complete mitochondrial DNA of 4 Przewalski horses, the split between the 2 subspecies of horses occurred much earlier, ~150,000 years ago.

I recently browsed the internet to find some pictures of Przewalski horses' hooves. In my opinion, it is always good to look at some structure with respect of the evolution of that structure, as the horse just like we humans, are a product of millions of years of evolution by natural selection. Below are some pictures that I think stem from horses that really live in the wild and also in some native steppe habitat, in which this subspecies of horse evolved, and not an Animal Park, such as San Diego Animal Park, or Tierpark Hellabrunn in Munich.

I think what is pretty obvious is that these hooves look less than "ideal" for our understanding. There are horses with extremely chipped hoof walls, high heels, and some with extremely long toes. Yet, they seem to be doing just fine. What these horses do not seem to have so badly is underrun heels. Underrun heels, as far as I understand it, is the main cause of navicular syndrome. How these horses maintain a good heel angle despite a long toe is the question. Maybe the toe just does not stay that long for a long time.

One point of consideration is that these horses nowadays (and in contrast to much of their evolutionary history), do not face any pressures from predation anymore. The Sabre Tooth tiger has been hunted to extinction by humans. It most likely was the major predator of large herbivores such as the horses in the steppes. It went extinct 11,000 years ago, as modern humans settled the continents out of Africa. The threads that the Przewalski horse faces nowadays is habitat loss.

So the question is how their hooves would be if natural selection would actually operate on those horses as it has done for millions of years before today.

extremely steep hairline angle