What are a few pieces of evidence that demonstrate how the horse has evolved since 33.9 million years ago?
1. Size and Appearance: The anatomy of the horse has changed significantly over millions of years. Fossils of the oldest known prehistoric horses called the Eohippus, dating back to 56 million years ago, were only about the size of a small dog. Over time, horses grew larger and developed longer limbs, which made them faster and better adapted to open grasslands. They also evolved longer, slimmer legs, a longer neck, and a larger skull compared to their predecessors.
2. Teeth and Digestive System: Over time, horses developed a more efficient digestive system capable of breaking down tougher plant material. This was made possible by the evolution of longer, more complex digestive tracts. Their teeth also changed, with the evolution of high-crowned teeth that could better grind down tough plant material.
3. Feet and Hooves: The modern horse's hoof is a specialized structure that has evolved over millions of years. Fossils show that horses once had toes, but over time, these toes became more elongated and eventually fused into the single hoof we see today. The horse's hoof is also harder and thicker than that of their ancestors, allowing them to run on hard surfaces.
4. Domestication: The domestication of horses has played a significant role in their evolution. Humans selectively bred horses for traits such as speed and endurance, resulting in the development of larger and more muscular breeds like the Thoroughbred, while other breeds became more specialized for work such as plowing or riding.
5. Brain Size and Intelligence: The horse's brain has also evolved over time, with the modern horse having a larger brain compared to their prehistoric ancestors. This increase in intelligence has allowed horses to adapt to changing environments and form complex social structures.