你是否曾为打嗝苦恼？你是否曾怀疑鸡皮疙瘩的用处？人类在进化的同时，也遗留了一些惹眼的不完美之处。它们与生俱来，无法抛却，却也见证了生命的玄奥。
Natural selection acts by winnowing1) the individuals of each generation, sometimes clumsily2), as old parts and genes are co-opted3) for new roles. As a result, all species inhabit4) bodies imperfect for the lives they live. Our own bodies are worse off5) than most simply because of the many differences between the wilderness in which we evolved and the modern world in which we live. We feel the consequences every day. Here are six. 
自然选择会通过淘汰每一代的个体达到优胜劣汰，但有时候淘汰的手段却很拙劣，比如给一些旧的器官和基因指派新的角色。结果就是，每个物种都拥有并不是完美适应他们各自生活的身体。我们人类的身体比大多数生物更糟糕，而这仅仅是因为我们进化时所处的野生环境和我们如今所处的现代世界之间存在诸多差异。每一天，我们都能感受到进化带来的后遗症。这里就有六个。
Goose bumps6) don't really help. 鸡皮疙瘩不管用。
When our ancestors were covered in fur, muscles in their skin called "arrector pili" contracted when they were upset or cold, making their fur stand on end. When an angry or frightened dog barks at you, these are the muscles that raise its bristling7) hair. The same muscles puff8) up the feathers of birds and the fur of mammals on cold days to help keep them warm. Although we no longer have fur, we still have fur muscles just beneath our skin. They flex9) each time we are scared by a bristling dog or chilled by a wind, and in doing so give us goose bumps that make our thin hair stand uselessly on end10).
我们的祖先身上覆有毛发，当他们感到紧张或寒冷时，皮肤上的肌肉“立毛肌”就会收缩，使毛发竖立起来。当一只发怒的或受了惊吓的狗朝你狂吠时，正是立毛肌让它的毛发倒竖。同样，立毛肌也让鸟类的羽毛和哺乳动物的毛发膨松起来，使它们在寒冷的天气里保持身体暖和。尽管我们人类不再有毛发，但我们的皮肤下还留存着立毛肌。所以每当我们被“怒发冲冠”的狗吓到或感到冷风带来的寒意时，立毛肌就会收缩，我们就会起鸡皮疙瘩。当然我们那稀疏的汗毛也会随之竖立起来，但已经起不到任何保暖作用了。
Our brains squeeze our teeth. 大脑挤掉智齿。
A genetic mutation11) in our recent ancestors caused their descendants to have roomy skulls that accommodated larger brains. This may seem like pure success—brilliance, or its antecedent12) anyway. But the gene that made way for13) a larger brain did so by diverting bone away from our jaws, which caused them to become thinner and smaller. With smaller jaws, we could not eat tough food as easily as our thicker-jawed ancestors, but we could think our way out of that problem with the use of fire and stone tools. Yet because our teeth are roughly the same size as they have long been, our shrinking jaws don't leave enough room for them in our mouths. Our wisdom teeth14) need to be pulled because our brains are too big.
在我们近代祖先身上发生的一次基因突变让后代的头颅变得更为宽敞，脑容量也随之变大。这看起来简直是有百利而无一害——让人类智慧超群，或者这至少是人类获得智慧的前提条件。但造成脑容量变大的根本原因是基因突变使得头骨与嘴部渐行渐远，我们的口腔则变得又窄又小。嘴巴变小后，我们便无法像我们的大嘴巴祖先那样轻松地咬食坚硬的食物了，但我们还可以想出自己的办法解决这个问题——使用火和石器。然而，我们的牙齿大小从古至今没什么变化，所以变小的嘴巴没有足够的空间容纳它们。因此，我们不得不因为大脑太大而拔掉智齿。
Obesity15) 肥胖
Many of the ways in which our bodies fail have to do with very recent changes, changes in how we use our bodies and structure our societies. Hunger evolved as a trigger to drive us to search out food. Our taste buds evolved to encourage us to choose foods that benefited our bodies (such as sugar, salt and fat) and avoid those that might be poisonous. In much of the modern world, we have more food than we require, but our hunger and cravings continue. They are a bodily GPS unit that insists on taking us where we no longer need to go. Our taste buds ask for more sugar, salt and fat, and we obey.
我们身体的很多无用之处都与近代的变化有着千丝万缕的联系，这些变化源于我们如何使用身体以及社会结构的构建方式。饥饿进化成为驱使我们寻找食物的动机。进化后的味蕾鼓励我们选择对身体有益的食物(比如糖、盐和脂肪)，避开那些有害食品。现代生活中，我们往往摄入超过身体需要的食物量，但饥饿感和对食物的渴望仍旧存在。它们就像身体的导航系统一样，即使我们已经不再需要，还是会坚定地指引我们不断吃下去。而我们的味蕾也要求更多的糖、盐和脂肪，于是我们便乖乖从命了。
We're awfully cold in winter. 冬天我们总是感到很冷。
Fur is a warm hug on a cold day, useful and nearly ubiquitous16) among mammals. But we and a few other species, such as naked mole rats, lost it when we lived in tropical environments. Debate remains as to why this happened, but the most plausible explanation is that when modern humans began to live in larger groups, our hair filled with more and more ticks17) and lice18). Individuals with less hair were perhaps less likely to get parasite-borne diseases. Being hairless in Africa was not so bad, but once we moved into Arctic lands, it had real drawbacks19). Evolution has no foresight, no sense of where its work will go.
对于哺乳动物来说，天冷的时候，毛发就像一个温暖的怀抱，既实用又普遍，可我们和其他少数物种(如光秃秃的鼹形鼠)却没有。当年我们生活在热带环境中时，我们的毛发就退化不见了。关于退化的原因人们仍然争论不休，但最合理的解释是，随着现代人类开始大规模群居，我们的毛发里聚集了越来越多的壁虱和虱子。也许，毛发较少的人最不可能得寄生虫传播的疾病吧。在非洲，没有毛发并不会太糟糕，但一旦我们迁居北极，那可真是个大麻烦。进化并没有先见之明，对自己所能造成的后果也毫无知觉。
Backaches 背痛
The backs of vertebrates20) evolved as a kind of horizontal pole under which guts21) were slung22). It was arched23) in the way a bridge might be arched, to support weight. Then, for reasons anthropologists debate long into the night, our hominid24) ancestors stood upright, which was the bodily equivalent of tipping a bridge on end. Standing on hind legs offered advantages—seeing long distances, for one25), or freeing the hands to do other things—but it also turned our backs from an arched bridge to an S shape. The letter S, for all26) its beauty, is not meant to support weight and so our backs fail, consistently and painfully.
脊椎动物的背部进化成了水平横杆状，下面悬挂着各类器官。它像拱桥一样弯曲着，这样才能承载重量。后来，由于种种原因(对此，人类学家日夜争论)，人类祖先开始站了起来，就像将拱桥斜着立起来似的。后腿站立是有一些优势——比如我们可以看得更远，还可以空出手来做其他事情——但它却使我们的背部从拱形变成了S形。字母S尽管看上去很美，却并不利于承载重量，这就是我们为什么总是感到腰酸背痛的原因。
Hiccups27) 打嗝
The first air-breathing fish and amphibians28) extracted29) oxygen30) using gills31) when in the water and primitive lungs when on land—and to do so, they had to be able to close the glottis32), or entryway to the lungs, when underwater. Importantly, the entryway (or glottis) to the lungs could be closed. When underwater, the animals pushed water past their gills while simultaneously pushing the glottis down. We descendants33) of these animals were left with vestiges34) of their history, including the hiccup. In hiccupping, we use ancient muscles to quickly close the glottis while sucking in (albeit air, not water). Hiccups no longer serve a function, but they persist without causing us harm—aside from35) frustration and occasional embarrassment. One of the reasons it is so difficult to stop hiccupping is that the entire process is controlled by a part of our brain that evolved long before consciousness, and so try as you might, you cannot think hiccups away.
最早呼吸空气的鱼类以及两栖动物在水中往往用鳃吸取氧气，在陆地则用原始的肺来呼吸。为了做到这一点，在水里时它们不得不关闭声门(也叫肺部入口)。重要的是，这个入口(声门)是能够被关闭的。这些动物在水下时，水流经鳃部的同时也将声门压了下去。而作为后代的我们也存留了它们历史的遗迹，打嗝就是其中之一。打嗝的时候，我们就是在吸气(虽然吸的是空气，而不是水)的同时用古老的肌肉迅速关上了声门。打嗝已经没什么用了，但却仍旧固执地留了下来，不过倒也没什么害处——除了给我们带来无奈和偶尔的尴尬以外。想让打嗝停下来实在很难，原因之一就在于，打嗝的整个过程都是由大脑的某一部分控制的，而这部分大脑在人类有意识之前就已经进化完成了。所以尽管去试吧，单靠意志力可没法儿让打嗝停止。
I have not even mentioned male nipples. I have said nothing of the blind spot in our eyes. Nor of the muscles some of use to wiggle36) our ears. We are full of the accumulated baggage of our idiosyncratic37) histories. The body is built on an old form, out of parts that once did very different things. So take a moment to pause and sit on your coccyx38), the bone that was once a tail. Roll your ankles, each of which once connected a hind leg to a paw. Revel39) not in who you are but who you were. It is, after all, amazing what evolution has made out of bits and pieces. Nor are we in any way alone or unique. Each plant, animal and fungus40) carries its own consequences of life's improvisational41) genius. So, if you will excuse me, I am going to rest my back.
列了这么多，我还没说到男性的乳头，关于眼睛里的盲点也只字未提，更没有讲到那些能让耳朵动起来的肌肉。我们身上到处都有各具特色的历史累积下来的包袱。我们的身体建立在陈旧的模型上，所用的零件在以前发挥着与现在大不相同的功用。因此，不妨先歇一歇，花些时间坐着感受一下尾骨，那曾是祖先的尾巴。转一转你的脚踝，它们都曾连接祖先的后腿和爪子。幻想并陶醉于祖先的样子，而不是现在的模样。毕竟，能够从零零碎碎的东西进化成现在这样是多么神奇的事啊！我们人类绝不是特例。每一种植物、动物和真菌都承受着生命的即兴创作才能带来的后果。那么，请见谅，我要让我的背部休息一下了。
1. winnow [ˈwɪnəʊ] vt. 筛选，选取
2. clumsily [ˈklʌmzili] adv. 笨拙地
3. co-opt [kəʊˈɒpt] vt. 指派
4. inhabit [ɪnˈhæbɪt] vt. 居住于
5. worse off: 情况更糟糕
6. goose bumps: [复] 鸡皮疙瘩
7. bristling [ˈbrɪs(ə)lɪŋ] adj. 竖立的
8. puff [pʌf] vt. 膨胀；肿胀(up, out)
9. flex [fleks] v. 收缩
10. on end: 竖着，直立着
11. genetic mutation: 基因突变
12. antecedent [ˌæntɪˈsiːd(ə)nt] n. 前提条件
13. make way for: 给……让路
14. wisdom tooth: 智齿
15. obesity [əʊˈbiːsəti] n. 肥胖
16. ubiquitous [juːˈbɪkwɪtəs] adj. 无所不在的，普遍存在的
17. tick [tɪk] n. 壁虱
18. lice [laɪs] n. 虱子，白虱［louse的复数］
19. drawback [ˈdrɔːˌbæk] n. 缺点；障碍
20. vertebrate [ˈvɜː(r)tɪbrət] n. 脊椎动物
21. gut [ɡʌt] n.［常作〜s］内脏
22. sling [slɪŋ] vt. 悬挂，吊挂
23. arched [ɑː(r)tʃt] adj. 弓形的；有拱的
24. hominid [ˈhɒmɪnɪd] adj. 【动】人科的(动物)
25. for one: 举个例子
26. for all: 尽管，虽然
27. hiccup [ˈhɪkʌp] n. 打嗝
28. amphibian [æmˈfɪbiən] n. 两栖动物
29. extract [ɪkˈstrækt] vt. 榨取；提取
30. oxygen [ˈɒksɪdʒ(ə)n] n. 氧气
31. gill [ɡɪl] n. 鳃
32. glottis [ˈɡlɒtɪs] n. 声门
33. descendant [dɪˈsendənt] n. 子孙；后代，后裔
34. vestige [ˈvestɪdʒ] n. 退化器官；残留部分
35. aside from: 除……以外
36. wiggle [ˈwɪɡ(ə)l] vt. 使扭动，使摆动
37. idiosyncratic [ˌɪdiəʊsɪŋˈkrætɪk] adj. 特殊的，特质的
38. coccyx [ˈkɒksɪks] n. 尾骨
39. revel [ˈrev(ə)l] vi. 陶醉，着迷；饱尝(in)
40. fungus [ˈfʌŋɡəs] n. 【植】真菌
41. improvisational [ˌɪmprəvaɪˈzeɪʃ(ə)nəl] adj. 即兴的；即兴创作的