Use the information and model to answer the following question.



Echippus is an early ancestor to modern horses that lived 40 million years ago. The organism had a short neck, a short tail and feet with four toes. After ten million years, the tail and neck became longer and one of the toes disappeared as evidenced by the fossil of Mesohippus. Evolution of these organisms continued for 20 million years up to the present day causing the organisms to have longer necks and one solid hoof.