The study of differential growth in various animals, including humans, suggests that a similar growth pattern occurs throughout the bilateral animals. This growth pattern is based on the assumption that a quadratic equation describes the relationship between two body measurements, yielding a quadratic parabola in a graphic representation. The study of differential growth by using a quadratic parabola gives the answers to the questions 'Why do we stop growing?' and 'Why are women shorter than men?'. The conclusions for various animals are amply illustrated by graphic representations.