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Science and technology
科學技術
The evolution of the hand
手的進化
Making a fist of it
拳頭的演化
How a dual-use bodily structure came into existence
人手的雙重功能如何生成
THE appendage at the end of a human being's arm is a strange organ.
與人類手臂相連的手掌是一個奇特的部位，也是人類唯一因不同用途而擁有不同名稱的部位。
It is the only one that has different names, depending on what it is being used for. Employ it to hold something, and it is called a hand. Employ it to hit someone, and it is called a fist.
拿物體，我們稱之為手；攻擊人，我們稱之為拳頭。
That second use, though, is almost unknown in other primates.
而幾乎所有的靈長類動物極少使用拳頭攻擊。
Most primate hands are long of palm and finger, short of thumb, and suited for climbing.
大多數靈長類動物的手是手掌寬大、手指較長和大拇指較短，這一結構有利于攀爬。
Human hands have short palms, short fingers and long thumbs, which are not.
人類的手是手掌短小、手指適中和大拇指較長，這一結構不利于攀爬，
These proportions do, though, make it possible to grip things in two ways that other apes' hands cannot manage well.
然而，手的這種比例結構使得人類比其它靈長類動物更擅長于抓取物體，抓取有兩種方式，
One is by using what is known as a precision grip, in which an object is held between the pads of the finger tips and the pad of the thumb.
一是精確握法，使用大拇指指尖與其它手指指尖抓緊一物體；
The other is by means of a power grip, in which all the fingers and the thumb are wrapped around what is being grasped.
另一種方式是力量握法，包括大拇指在內的所有手指把一物體緊緊包住。
These two grips are crucial to Homo sapiens's characteristic tool-crafting skills, and it has thus long been thought that the widespread use of tools by humanity's ancestors was the driving force behind the modern hand's proportions.
以上兩種握法是智人在使用工具上的關鍵特征，因此，長期以來人們認為人類的祖先廣泛使用工具是驅使人類手部結構進化的推動力。
No doubt that was important. But a study just published in the Journal of Experimental Biology by Michael Morgan and David Carrier of the University of Utah has shown that the exact geometry of the hand is probably the result of its destructive rather than its constructive power.
毋庸置疑，廣泛使用工具對人手的進化起到了重要的作用，但是，由猶他大學的生物學家邁克爾摩根與戴維卡里爾合作完成，并在最近刊登在《實驗生物學雜志》的一篇論文里寫道，人類手部的精確幾何結構可能是破壞性力量導致的結果，非建設性力量導致的結果。
Most natural weapons are obvious: teeth, claws, antlers, horns.
諸如牙齒、爪子、鹿角、牛/羊角等大多數的天然武器是很直觀的。
But the hand becomes a weapon only when it turns into a fist.
而手只有在變成拳頭的時候才成為武器。
Dr Morgan and Dr Carrier therefore studied its anatomy to try to find out what makes the fist such an effective weapon—one which, like the precision and power grips, the hand of even a chimpanzee is incapable of forming properly.
所以，摩根與卡里爾兩位教授想通過解剖學來揭開拳頭成為有效武器的之謎，其中包括連黑猩猩都做不到的精確握法與力量握法。
Part of the reason is obvious.
有一點是很明顯的：
A fist presents the knuckles first.
拳頭是關節往外凸，
That means the force of a blow is transmitted through a much smaller area than would be the case for its alternative, an open-handed slap.
這意味著擊打的接觸面比掌擊的接觸面要小。
But the two researchers suspected that there might be more to it than that, so they dug a little deeper.
但兩位教授認為原因不僅僅如此，于是，他們進一步深入研究。
First, they gathered some basic measurements.
首先，摩根與卡里爾兩位教授收集了一些基本的測量數據。
They asked ten athletes—a mixture of boxers and martial artists—to strike a punch bag as hard as they could using either a normal fist or an open palm.
他們邀請了十位運動員，包括拳擊手和格斗選手，要求他們用盡全力用拳頭打沙袋或者掌擊沙袋。
The athletes did so in many ways, including forward strikes, side strikes and overhead attacks, and Dr Morgan and Dr Carrier monitored how much force was delivered in each case using an accelerometer attached to the bag.
十位運動員以沖拳、測拳和高拳等方式擊打沙袋。通過在沙袋上捆綁的加速計，兩位教授監控到使用拳頭打擊或掌擊在不同的擊打方式下的力度。
They also used a series of pistons to measure the stiffness of different hand shapes.
除此之外，兩位教授還使用了一系列的活塞來測量選手擊打時手的不同姿勢的硬度。
These included a fully clenched fist, a semi-fist with the fingers curled up but the thumb pointed outwards, and a poorly formed fist in which the fingers were folded over the palm and the thumb pointed outwards.
這些姿勢包括全握拳頭、半握拳頭以及虛拳。
As the athletes formed these various fists and fist-like shapes, the pistons measured the rigidity of their hands along the knuckle bones.
從選手擺出手型準備出擊到完成擊打，活塞測量了他們手指關節的硬度。
Though the accelerometer in the punch bag suggested that a sideswipe made with a closed fist delivers 15% more force than an open-handed strike, a frontal attack with either produces about the same force.
盡管在沙袋里的加速計的數據顯示，拳擊的近距離側擊比掌擊能傳遞多15%的能量到沙袋上，但正面攻擊沙袋時，無論是拳擊還是掌擊，傳遞到沙袋上的能量都差不多。
The fist's advantage thus seems to be mainly in its geometry rather than it mode of delivery.
由此看來，拳頭的優勢是得益于幾何學而不是能量傳遞的方式。
Part of that advantage does, indeed, come from the small surface area of the knuckles.
拳頭的指關節面積小，這是一個優勢。
But the killer app, almost literally, is the stiffness imparted by the way the bones are arranged in a properly formed fist.
理論上，拳頭的硬度源于手指骨組合方式的完美性。
This allows the force of a punch to be delivered with an effect that can, for the receiver, be bone breaking.
這樣，力量能夠以有效的方式傳遞至目標而不至于使手指骨斷裂。
Two things are crucial.
有兩個因素很關鍵。
One is the way the fingers curl back on themselves, which leaves no empty space inside the fist.
一個是握拳時手指緊密地彎曲，中間不留任何空隙，
That is a product of the precise lengths of the component bones of each finger, which is one reason a chimpanzee cannot form a proper fist.
這可是每根手指骨以精確的尺寸構建的產物，這是黑猩猩的手無法做到的。
The other is the buttressing role of the thumb, which adds yet further stiffness.
另外一個因素是大拇指的支撐作用使得拳頭更加堅硬。
Again, this requires the thumb to be of precisely the right length, and to originate in precisely the right place at the side of the palm.
當然，大拇指的精確尺寸以及所處的位置兩者相結合才能使之完美地發揮了作用。
In combination, Dr Morgan and Dr Carrier's machine indicted, these features make a properly formed fist almost four times as rigid as a chimpanzee-style fist—for when a chimp curls its fingers up it leaves a gap through the middle of the fist, fatally weakening the structure; and the thumb plays no buttressing role.
摩根與卡里爾兩位教授綜合利用了測量出的各種數據，他們認為正是以上所描述的兩種因素讓人拳頭的硬度是黑猩猩拳頭硬度的四倍，當黑猩猩的手握成一個拳頭時，牠彎曲的手指中有一個空隙，這是一個致命性的缺陷，而且靈長類動物的大拇指也不起到支撐拳頭的作用。
All this suggests that fists are indeed proper evolutionary adaptations, with their own history of natural selection, rather than being just the coincidental by-products of humanity's handiness with a tool.
綜上所述，人手之所以能形成拳頭是大自然物競天擇的結果，而不是人類碰巧使用工具所進化的副產品。
In fact, it is probably easier for the gripping role of the hand to adjust to the geometrical requirements of the punching role of the fist than the other way round.
實際上，很可能人手的抓取功能是為了適應拳頭的幾何結構而進化過來的，而不是抓取功能的副產品。
Which makes perfect sense, for it has long been the case that the species is divided between those who prosper by making things with their hands, and those who rely on their fists, or the threat of them, to take what the makers have made.
這就說明了，在很長一段時間里，物種之間的差異是根據使用手的不同方式開始，一些使用雙手制造物品、一些利用拳頭自我保護或者使用武力搶奪前者所制造的物品。
