An infant's body has about 300 bones at birth. These eventually fuse (grow together) to form the 206 bones that adults have. Some of a baby's bones are made entirely of a special material called cartilage (KAR-tel-ij).

Other bones in a baby are partly made of cartilage. However, the number of bones an individual has varies developmentally. In fact, a person has the most bones when they are an infant. A person has less bones as an adult. Over the course of development, some of a person's bones fuse together, so that by the time the person reaches adulthood, the number of bones in the body is 206.

See: https://en.wikipedia.org/wiki/Bone

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