1.你的皮肤有四种颜色。所有的皮肤,未经染色,都将呈现出乳白色。皮肤的浅表血管为其增添了一抹酡红色。黄色色素给皮肤着淡淡的黄色。最后,为抵御紫外线辐射而制造的深褐色的黑色素,会大量呈现出黑色。2.进化并不是完美的。否则,我们可能会拥有一对翅膀而不是智齿。有时候,一个物种长些没用的器官,仅仅因为它们不会造成太大的危害。但智齿并不总是为牙科医生准备的一 Your skin has four colors. All the skin, without staining, will appear milky white. Skin of the superficial blood vessels to add a touch of 酡 red. Yellow pigment to the skin with a faint yellow. Finally, dark brown melanin, which is made to protect against UV radiation, appears heavily in black. 2. Evolution is not perfect. Otherwise, we may have a pair of wings instead of wisdom teeth. Occasionally, organs of a species that grow useless simply because they do not cause much harm. But wisdom teeth are not always prepared for dentists