Babies are born with around 270 bones. Adults have 206.
Many of a newborn's bones are separate pieces of cartilage and bone that fuse together as the child grows. The skull alone starts as several plates with soft gaps between them.
Why is this true?
Separate pieces let the skull flex during birth and let bones grow at their ends. The last fusions happen in the early twenties, which is why age can be estimated from a skeleton.
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More about human body
Your own body is a reliable source of surprises. It replaces cells by the million every second, keeps bacteria that outnumber human cells, and runs sensory tricks that make the world feel smoother than the raw signal ever is. The facts collected here stick to mainstream physiology, avoid the wellness myths that circulate alongside them, and explain the underlying mechanism rather than just quoting a startling number.