The study looked at the foot bones of Japanese macaques to see how they grow and change over time. They found that the size and shape of the foot bones change differently as the monkeys grow up. The main bones in the foot grow at different rates compared to the overall size of the foot. The front part of the foot grows differently from the back part as the monkeys get older. This shows that the way the foot bones grow in young monkeys is not the same as in adult monkeys.