Babies are born with approximately 270 to over 300 bones, depending on the source, with many of these bones being partly made of cartilage
. This higher number compared to adults is because some bones are initially separate and later fuse together during growth and development. By adulthood, the typical number of bones decreases to 206 due to this fusion process
. The fusion occurs as cartilage is gradually replaced by bone through ossification, and separate bone elements join to form larger bones. For example, the skull starts with about 44 separate elements that fuse over the first year or so of life, and some bones like the collarbone continue to fuse until the early to mid-twenties
. This process explains why infants have more bones than adults. In summary:
- Number of bones at birth: about 270 to 305 (varies by source)
- Number of bones in adulthood: typically 206
- Reason for difference: fusion of bones during growth and ossification replacing cartilage with bone
