Nature didn't need to because, unlike the abalone shell, the survival of a species didn't depend on building those materials, until maybe now when it might just matter.
之所以这样是因为大自然不会像鲍鱼壳， 除非到现在，只有当这种材料变得很重要， 或许只有生成这种材料， 各物种才会生存下来，大自然才会生成它。