How might one breed of modern horse evolve if the breed were to exist in the wild, without interaction with humans?

Paper details:

Complete a timeline showing the evolution of horses over the past 54 million years from Hyracotherium to Equus. Include how traits like size, hooves, teeth shape and composition have changed over time. Link the changes to changes in the environment and niche (for example, what conditions resulted in longer limbs or shorter muzzles).
Select one breed of modern horse, such as the Arabian, Morgan, Shire or Quarter horse. Outline three of the traits that that breed has been selectively bred for by humans and how these traits have been influenced by how the breed is used by humans.
Next indicate how your think your horse would evolve if it was “lost” in an area without humans (like the Sable Island Ponies were lost) by specifically describing how the traits you indicated would change and why. Ensure you describe the area and the factors that will influence the evolution of your horse such as climate, other species present, types of vegetation, availability of resources etc. and use unit specific vocabulary to indicate and support the types of selection (such as competition, genetic drift or stabilizing selection) occurring.
Provide a “before” and “after” picture of your breed. You will have to draw the “after” picture yourself.