Over a period of approximately 40 million years, the picture depicts the evolution of horses.
Overall, the changes in horse are the result of natural selection, and the process is not cyclic but rather progresses in a linear direction. There are four stages in their evolution, starting from the early and ending with the modern horse.
In the initial stage, the horse was known as Eohippus, dating back approximately 40 million years. It was relatively small in size and bore little resemblance to modern horses, possessing 5 digits. Around 30 million years ago, it evolved into Mesohippus, which was markedly larger and had a longer tail. The number of toes decreased from five to three, with the middle toe being slightly larger than the two side toes.
Moving on to the two more recent years, Merychippus appeared around 15 million years ago. It bore a much closer resemblance to the moder horse, featuring a stronger body and a more prominent mane. Its middle toe also became larger and longer than in the previous two stages. Finally, the modern horse emerged with a longer tail, a thicker mane, and a single large, sturdy hoof formed by the fusion of the three toes.
