But also imagine if they were filled with solid bone -- our head would be dead weight, we wouldn't be able to hold it erect, we wouldn't be able to look at the world around us.
하지만 또한 생각해보세요. 두개골이 빽빽하게 뼈로 채워져 있었다면, 머리는 엄청난 무게여서 바로 들지도 못할 것이고, 우리 주변을 바라보지도 못할 것입니다.