Question

Fossils of ancestors of the modern horses show a small, 4-toed, almost dog-like browsing animal named Eohippus. Over time, the horses got larger, lost toes, and changed to a grazing diet. What is the best explanation for why this change occurred?

Answer 1

The change from the ancestral Eohippus to modern horses is explained by evolutionary adaptations to environmental changes and natural selection, leading to larger size, hoof development, and specialized teeth for grazing.

Step-by-step explanation:

The best explanation for the change from the small, 4-toed Eohippus to modern horses is evolution due to environmental changes and natural selection. As the climate became drier and marshlands were replaced with grasslands, horses evolved to have physical traits better suited for their new ecosystem. They increased in size to better spot predators, lost toes and developed hooves for faster running to escape predators, and their molars adapted for grinding tough grasses which became their primary food source, demonstrating an example of evolutionary adaptation.

Significant fossil evidence supports this evolutionary process, showing a 57 million year transformation in the horse lineage. This can be seen in various intermediate fossils such as those of Mesohippus, indicating a dietary shift and physical changes over millions of years, and is further demonstrated by the later emergence of species such as Hipparion. The fossil record clearly tracks these anatomical changes and dietary shifts in response to a changing environment, illustrating an extraordinary example of evolutionary biology.

Answer 2

The best answer would be it has happened because of natural selection.
Over many generations, natural selection selects the traits that bring advantages to it's holders. In the case of the horse ancestors, the traits selected were all adaptation to living in the steppe, the vast grasslands.
Over time, the individuals who could run the fastest and avoid the predators and utilize the resource that is most available in the grasslands- grass would be the most successful, leave more offspring and eventually be more prevalent in the population.