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　　为什么人类身上没有斑点或条纹?

Why Don’t Humans Have Spots Or Stripes?

为什么人类身上没有斑点或条纹?

Have you ever wondered why we humans don’t have spots or stripes? Well, maybe you haven’t, but it is interesting that so many creatures are multicolored but we are not.

你是否曾经好奇过为什么我们人类身上没有斑点或条纹?也许你没想过，可那么多生物五彩斑斓，我们却不是，这很有意思。

Melanin Pigments

黑色素

Humans and animals get their skin color from melanin pigments, which can be either black or yellow. Together, these two pigments account for just about every color you might see on the skin of mammals: white, red, yellow, brown, and black and every shade in between.

人类和动物的皮肤颜色来自黑色素，它不是黑色就是黄色。二者混合可呈现你能见到的各种哺乳动物的皮肤颜色：白色、黄色、棕色、黑色和他们之间的过渡色。

The skin cells that produce melanin are known as melanocytes. In the embryos of mammals, the melanocytes originate from the same group of cells that produces the spinal cord and the brain. From there, these cells migrate through the developing skin towards the belly of the animal.

产生黑色素的皮肤细胞是黑素细胞，在哺乳动物的胚胎中，黑素细胞源自制造出脊髓和大脑的同组细胞。这些细胞从那里出来通过皮肤的生长迁往动物的肚子。

Streaks and Stripes

条纹和条痕

If the melanocytes that produce dark pigments and light pigments migrate in streaks, you end up with stripes. The same goes for spots, but in this case, only random patches of certain pigments survive. In either case, the migration pattern is genetically determined.

如果产生深浅色素的黑素细胞以条纹状迁移，那么你身上就有条纹。斑点也是这么来的。但在这种情况下， 只有随机的某些色素斑点能够存活。不论哪种情况，其迁移方式由基因决定。

For certain species, like zebras, stripes provided an evolutionary advantage because they worked as camouflage. Those animals with stripes were more likely to survive, and to pass along the genes that produce stripes to their offspring. For humans, this apparently wasn’t the case. However, it’s likely that our overall skin color probably is a result of adaptation as well.

对于特定物种 ，比如斑马， 条纹因可作为伪装对进化有利。身上有条纹的动物更有可能生存下来，并把能产生条纹的基因传给后代。对于人类来说，情况显然不同。但是我们全身皮肤的颜色也可能是适应环境的结果。

　　亚硫酸盐是什么?

What Are Sulfites?

亚硫酸盐是什么?

You’ve just opened a bottle of wine for dinner. On the label, you see these words: Contains Sulfites. What are sulfites? And what are they doing in your wine?

设想一下，你在晚餐时刚刚打开了一瓶酒，你会在酒瓶的标签上看到：含亚硫酸盐。亚硫酸盐是什么?这些成分在你的酒中发挥什么样的作用呢?

Chemical Compounds

化合物

Sulfites are chemical compounds found naturally in grapes, garlic and other plants. Thousands of years ago, people realized something nifty about sulfites: they kill or slow the growth of bacteria and most yeasts. This comes in handy for winemakers, who add specific yeasts to ferment wine, and don’t want wild yeasts or bacteria to spoil it. Sulfites prevent spoilage in wine, acting as a preservative.

亚硫酸盐是在葡萄，大蒜和其他植物中常见的一种化合物。几千年前，人们就发现了亚硫酸盐的一些妙用：它们能杀死细菌，或者降低细菌滋生和发酵的速度。这个发现对于酿酒师来说是非常重要的，他们通常会在酒中加一些特定的酵母使酒发酵，但是同时，他们又不想野生酵母和细菌破坏了这个过程。而亚硫酸盐就能阻止酒的腐坏，在其中发挥了防腐剂的作用。

The amount of sulfites naturally in grapes is very small, and there’s a bit more produced during fermentation. But to take full advantage of sulfites’ preservative abilities, winemakers add a little more to the process. The Egyptians sterilized wine containers with sulfites, and sulfites have been added to wine for hundreds of years.

葡萄中含有亚硫酸盐的量非常少，在发酵过程中数量会有稍许的增加。但是，为了有效利用亚硫酸盐的防腐作用，酿酒师们通常会在酿酒过程中多添加一点点亚硫酸盐。埃及人也曾使用亚硫酸盐对酒类容器进行杀菌，而且，亚硫酸盐被添加进入酒类也已经有了几百年历史了。

Wine And Sulfites

酒和亚硫酸盐

So the relationship between wine and sulfites goes way back. But in 1985, the Food and Drug Administration required wine with added sulfites to say so on the label. Why?

因此，酒和亚硫酸盐的关系其实可以回溯到很久很久以前。但在1985年，食品与药品管理局要求，若酒类有添加亚硫酸盐，需要在标签上注明，为什么?

Researchers had recently discovered that less than one percent of the population is sensitive to sulfites. Most have mild reactions, like an itchy rash. But some folks have life-threatening reactions, including difficulty breathing and low blood pressure.

因为有研究人员之前发现，有不到1%的人会对亚硫酸盐产生过敏反应，虽然多数人的反应比较轻微，比如说会起很痒的皮疹，但有部分人的过敏反应会威胁到生命安全，这些反应包括呼吸困难或低血压等。

These rare but serious reactions are most often seen in asthmatics. Not all asthmatics are sensitive to sulfites, but the label’s there for those who need to steer clear. As the old saying goes, in wine–and now on the label–there is truth!

我们经常会在哮喘症患者身上看到这些少有但严重的反应。其实，也并不是所有的哮喘症患者都会对亚硫酸盐过敏，标签上的说明只是为了警示需要注意的人避开这些成分。就像老话常说的那样，酒后，现在是标注在标签上-吐真言!