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After visiting the zoo or watching an animal documentary, you may find yourself pondering this classic conundrum: Are zebras black with white stripes or white with black stripes? Though it may sound like a philosophical query, it is possible to answer this question with science. To do so, we need to take a look at the microbiology of the hairs that give zebras their dual-colored pattern.

从动物园回来后或在观看一部动物纪录片后，你也许会发现自己在思考一个非常经典的问题：斑马到底是黑底白纹，还是白底黑纹？尽管这个问题听起来有点哲学色彩，但是科学可以帮我们找到问题的答案。为了寻找这一答案，我们需要从微生物学的角度来观察让斑马呈现两种颜色的毛发。

Conundrum:令人迷惑的难题/a confusing problem or question that is very difficult to solve

Microbiology：微生物学

Zebras have black skin beneath their fur, but that doesn't mean that their stripes are necessarily white on black. The majority of a zebra's hairs are white—including the ones that grow on their bellies and inner legs, where their stripes appear to end. This suggests that the quadrupeds are white with black stripes, but according to Live Science, this is still the wrong way to look at the question.

斑马毛的下面是黑色的皮肤，但这并不一定就表示斑马为黑底白条纹。斑马毛大部分是白色的-包括长在肚皮和腿内侧的毛（条纹到肚皮和腿内侧就消失了）。这表明四足动物的毛是白色并带有黑条纹的。但是，根据“生活科学”（Live Science）的介绍，这并非是这一问题的正确答案。

Quadruped：四足动物

The true answer lies in a class of cells called melanocytes. Melanocytes are responsible for producing a pigment called melanin, which gives zebra hairs—and the hair and skin of all animals—their color.

真正的答案是一种细胞，这种细胞被称为黑素细胞。黑素细胞会产生一种叫做黑色素的色素，这种色素会使斑马毛-以及所有动物的毛皮呈现出自己的颜色。

Melanocytes：黑素细胞

When a zebra grows fur, melanocytes in their follicles dictate whether a strand will be light or dark depending on where it is on their body. In their normal state, these cells create the high-melanin black fur that makes up half of a zebra's signature coat. White zebra hairs contain no melanin, and they come from melanocytes that have been "turned off."

当一匹斑马长大时，毛囊中的黑素细胞会根据毛在身体上的位置来决定它的颜色是深的还是浅的。在正常状态下，这些细胞会形成黑色素含量高的黑毛，这样的黑毛占斑马标志性颜色的一半。斑马身上白色的毛里没有黑色素，这些毛来自于被“关掉”的黑素细胞。

Genetically speaking, zebras grow black hair by default, which makes the animals black with white stripes.

从基因角度来讲，斑马默认长黑毛，这使得它看上去是黑色并带有白色条纹的。

While that solves one part of the zebra stripe mystery, scientists still don't know why they sport their striking stripes to begin with. One commonly held belief is that the busy pattern confuses predators trying to pick a single zebra out of the herd. Research from 2014 supports the theory that the stripes deter insects by disrupting the polarization of reflected light, which is known to attract biting horse flies. The stylish look is just a bonus.

尽管科学理论部分解决了斑马的条纹之谜，但是科学家们仍旧不清楚为什么斑马从一开始就呈现出醒目的条纹。一个普遍的观点是，密集的图案会让捕食者很难从一群斑马中选出一匹斑马。2014年的研究证实了一个理论。这个理论是条纹可以通过破坏反射光的偏振来阻止蚊虫。而反射光的偏振可以吸引牛虻叮咬。时髦的外观只是一个额外的优点。

[h/t Live Science]   编辑&翻译：Sarah，上海译锐翻译