Humans are born with about 300 bones, but these fuse together as we grow. By the time a person is an adult, they only have 206 bones. One of the most obvious cases of bones fusing is that of the human skull. Although babies have a soft spot on their heads, as they grow, the bones of the skull fuse and harden, covering it. This fusing doesn't happen overnight though: the last bone solidifies in the body around the age of 18.
More talking points about bones: