'Also, with feral herds, there is natural selection. Horses who have poor enough conformation will be eaten by predators. With people, horses with poor conformation are only susceptible to the ailments associated with that conformation and not the actual threat of death (at least not immediately). So theoretically, most of the horses in the herd have decent enough conformation (i.e. topline if need be) to survive the next day. A horse with really poor topline, may be the slowest horse and therefore the next one eaten.'
There are a LOT of 'poorly conformed' horses in the wild. How many mustangs have you seen with an AMAZING shoulder? Or a great croup? This is because good conformation to US has NOTHING to do with surviving in the wild. Mustangs have no topline--the only thing they have to do is walk, graze, and on occasion, run. Galloping is also something that is not done all on the hind end--usually it's 50/50. Race horses are taught to lean on the reins to run, and the gait is 'flat'. And I think race horse trainers would know how to get a horse to run the fastest. ;) Poor topline has nothing to do with speed.
I never said horses needed impeccable conformation to survive, I said they need to have "decent enough" conformation, to survive to the next day. I also said "THEORETICALLY." It's survival of the fittest, natural selection. Of course a horse doesn't need even decent conformation, technically. As long as their legs are sound enough to run, they're good. However, a lot of conformation issues lead to lameness, and if its serious enough, a wild horse could be supper. If a horse can't move quickly enough, its not going to survive. True wild horses faced a lot more predators than they do now, wild horses in the west face what.. IDK I assumed wolves and mountain lions, to be honest I'm not sure they would even be bothered enough to catch a horse... However the horse would still perceive them as a threat, they would sense them as a predator and they would still run, regardless. I'm sure a dead lame horse who can't walk in the wild (due to what else, horrible leg conformation, and a year too many of carrying its own weight) might be preyed upon, especially if the herd left it. I was also stating theoretically because I meant true wild horses, waay before domestication..
Also you are taking my words waay too literally, naturally a horse who was 100% off their forehand would be rearing
(That was sarcasm). I said that yes, to be as light as possible the horse would have to lift its back and front end. The result is still the same, the horse is lifting up their back, and flexing their topline muscle, something they normally don't do otherwise. If the horse was too much on its forehand when it was running, it would lose balance from all the unequally distributed speed and stumble and fall. In the wild, that might equal slowest horse. Slowest horse equals next meal. Technically, the horse wasn't utilizing his topline
muscle, and lifting his back and lightening his front end... You see where I'm going with this.
I think a poorly developed topline muscle has to do with speed, more so endurance, but it still has a lot to do with speed. A lot relies on the individual horse, breed type, etc. but if the experiment could be done with two identical horses in all respects, except one horse has a developed topline and one doesn't, the horse with the developed topline is going to win.
I'm not saying that my pretty little Morgan who has a nice developed topline is going to win in a race against a thoroughbred with a poorly developed topline.
It's a muscle but in times of extreme peril (i.e. for the wild horse) the flight response will take over, and topline doesn't matter so much because hormones in the brain take over for the horse. The horse still has to be able to flex that muscle and lift his back. Done often enough, its called developing topline.
The question was, what does topline play in the wild? I think I answered it sufficiently and truthfully if you choose to read what I am saying and not take each word literally. I'm aware of how poorly built horses are in the wild, the idea of conformation is something that humans fathomed when studying horses, but some of the ideas would still play a role with wild horses from 3,000 years ago. Their anatomical structure has everything to do with survival, that includes the muscoskeletal system as a whole, and therefore conformation.