> About a quarter of the bones in your body are located in which area?And the answer: hands. The adult human has 206 bones in their body, and your hands have a total of 54bones between them. Did you know that when you're born, you have close to 300bones? Many of them fuse together as you grow.Interestingly, animals with skeletons did not exist until about 550 millionyears ago. When oxygen levels on the planet began to climb, the chemistry of theoceans changed in such a way that allowed animals to harness the mineralsnecessary for constructing hard structural parts. Agents of land erosion, suchas wind and rain, pushed a flood of aragonite and calcite into the oceans(minerals necessary in the development of calcium), which further fueled theevolution of skeletons. Today, the human body has evolved to rely on its skeleton for protection,mobility and overall function. Our bodies exist in such a way that each bonereports to the next; our own well-oiled and well-structured machine. If one boneis broken, those which surround it are unable to perform properly. There is onlyone bone that exists apart from any other: the hyoid bone in your throat. Eventhat is nestled away, largely protected by other forms of bodily defense.Did you know?The collagen in your bones constantly replenishes itself. So, about every sevenyears, you have a "new" skeleton!Check out this Crash Course video for more on our bodies' resilientinfrastructure: