The diagrams show how horses evolved through four main stages during their 40 million year evolution period. The horse developed larger body size and increased muscle strength during its evolutionary journey. The horse evolved through multiple stages until it reached its current form which has one hoof and feet that were originally developed between two and five toes.
Eohippus represents the first horse species which existed forty million years ago as a small creature. The animal possessed a back that curved and legs that were short in length. The animal used its small toes which formed its foot structure to walk on soft surfaces. The first Mesohippus emerged around 30 million years ago. The animal had larger dimensions but its body size remained between its two ancestors. The creature displayed three visible toes, which marked the beginning of toe reduction, but it maintained three toe existence.
The Merychippus species existed from 15 million years ago until its present time The animal had greater size and developed body features which resembled a horse. The animal maintained three toes, but its middle toe developed greater strength than its other two toes.
The modern horse represents the final evolutionary stage because it has developed into the largest horse species, which has developed strong leg muscles. The modern horse species developed a single hoof structure for running, which enables it to run faster and more efficiently than its ancestors.