The horse-donkey-mule phenomenon is an example of speciation in progress. Occasionally a fertile mule does turn up, and it would happen more often if horses and donkeys were intermingling freely in the wild. Sooner or later, there would be multiple mules who could interbreed with each to produce viable, fertile mule offspring, but could not interbreed successfully with horses or donkeys. That’s the point at which you’d have a new species. If you gave some researchers a few million dollars and 20 years or so, they could probably accelerate the process and deliver the new species in that short time frame by careful breeding with genetic analysis of each of the mules they tried to interbreed. In nature, it would take a lot longer, unless a bunch of fertile mules happened to get isolated together somewhere.
On the farm I bred a wild turkey (that flew into my turkey pen where I had my Royal Palm turkeys) I Tom and 3 females. The wild tom and my palm tom got into a bloody fight and I had to put on heavy gloves to go in the break them loose from each other. It was a bloody mess, but I threw the wild turkey into the back room of the chicken coop and gave him a female to breed with....All of the offspring looked like the wild turkey, but the second generation came out with both royal Palm and wild turkey. Plus a nestles cocoa brown solid one..
With such genetics your breeding color variations not new species..
Horse, donkey, mule, zebra, pony, all look very similar to me. For some reason God didn’t want Mules to breed. He had his reasons. They still look like horses not birds or cats. Not turning into humans any time soon.