经济学人下载:手的进化 拳头的演化

Science and technology
科学技术

The evolution of the hand
手的进化

Making a fist of it
拳头的演化

How a dual-use bodily structure came into existence
人手的双重功能如何生成

THE appendage at the end of a human being's arm is a strange organ.
与人类手臂相连的手掌是一个奇特的部位，也是人类唯一因不同用途而拥有不同名称的部位。

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.
拿物体，我们称之为手；攻击人，我们称之为拳头。

That second use, though, is almost unknown in other primates.
而几乎所有的灵长类动物极少使用拳头攻击。

Most primate hands are long of palm and finger, short of thumb, and suited for climbing.
大多数灵长类动物的手是手掌宽大、手指较长和大拇指较短，这一结构有利于攀爬。

Human hands have short palms, short fingers and long thumbs, which are not.
人类的手是手掌短小、手指适中和大拇指较长，这一结构不利于攀爬，

These proportions do, though, make it possible to grip things in two ways that other apes' hands cannot manage well.
然而，手的这种比例结构使得人类比其它灵长类动物更擅长于抓取物体，抓取有两种方式，

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.
一是精确握法，使用大拇指指尖与其它手指指尖抓紧一物体；

The other is by means of a power grip, in which all the fingers and the thumb are wrapped around what is being grasped.
另一种方式是力量握法，包括大拇指在内的所有手指把一物体紧紧包住。

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.
以上两种握法是智人在使用工具上的关键特征，因此，长期以来人们认为人类的祖先广泛使用工具是驱使人类手部结构进化的推动力。

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，广泛使用工具对人手的进化起到了重要的作用，但是，由犹他大学的生物学家迈克尔摩根与戴维卡里尔合作完成，并在最近刊登在《实验生物学杂志》的一篇论文里写道，人类手部的精确几何结构可能是破坏性力量导致的结果，非建设性力量导致的结果。

Most natural weapons are obvious: teeth, claws, antlers, horns.
诸如牙齿、爪子、鹿角、牛/羊角等大多数的天然武器是很直观的。

But the hand becomes a weapon only when it turns into a fist.
而手只有在变成拳头的时候才成为武器。

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，摩根与卡里尔两位教授想通过解剖学来揭开拳头成为有效武器的之谜，其中包括连黑猩猩都做不到的精确握法与力量握法。

Part of the reason is obvious.
有一点是很明显的：

A fist presents the knuckles first.
拳头是关节往外凸，

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.
这意味着击打的接触面比掌击的接触面要小。

But the two researchers suspected that there might be more to it than that, so they dug a little deeper.
但两位教授认为原因不仅仅如此，于是，他们进一步深入研究。

First, they gathered some basic measurements.
首先，摩根与卡里尔两位教授收集了一些基本的测量数据。

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.
他们邀请了十位运动员，包括拳击手和格斗选手，要求他们用尽全力用拳头打沙袋或者掌击沙袋。

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.
十位运动员以冲拳、测拳和高拳等方式击打沙袋。通过在沙袋上捆绑的加速计，两位教授监控到使用拳头打击或掌击在不同的击打方式下的力度。

They also used a series of pistons to measure the stiffness of different hand shapes.
除此之外，两位教授还使用了一系列的活塞来测量选手击打时手的不同姿势的硬度。

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.
这些姿势包括全握拳头、半握拳头以及虚拳。

As the athletes formed these various fists and fist-like shapes, the pistons measured the rigidity of their hands along the knuckle bones.
从选手摆出手型准备出击到完成击打，活塞测量了他们手指关节的硬度。

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.
尽管在沙袋里的加速计的数据显示，拳击的近距离侧击比掌击能传递多15%的能量到沙袋上，但正面攻击沙袋时，无论是拳击还是掌击，传递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.
由此看来，拳头的优势是得益于几何学而不是能量传递的方式。

Part of that advantage does, indeed, come from the small surface area of the knuckles.
拳头的指关节面积小，这是一个优势。

But the killer app, almost literally, is the stiffness imparted by the way the bones are arranged in a properly formed fist.
理论上，拳头的硬度源于手指骨组合方式的完美性。

This allows the force of a punch to be delivered with an effect that can, for the receiver, be bone breaking.
这样，力量能够以有效的方式传递至目标而不至于使手指骨断裂。

Two things are crucial.
有两个因素很关键。

One is the way the fingers curl back on themselves, which leaves no empty space inside the fist.
一个是握拳时手指紧密地弯曲，中间不留任何空隙，

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.
这可是每根手指骨以精确的尺寸构建的产物，这是黑猩猩的手无法做到的。

The other is the buttressing role of the thumb, which adds yet further stiffness.
另外一个因素是大拇指的支撑作用使得拳头更加坚硬。

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.
当然，大拇指的精确尺寸以及所处的位置两者相结合才能使之完美地发挥了作用。

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.
摩根与卡里尔两位教授综合利用了测量出的各种数据，他们认为正是以上所描述的两种因素让人拳头的硬度是黑猩猩拳头硬度的四倍，当黑猩猩的手握成一个拳头时，它弯曲的手指中有一个空隙，这是一个致命性的缺陷，而且灵长类动物的大拇指也不起到支撑拳头的作用。

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.
综上所述，人手之所以能形成拳头是大自然物竞天择的结果，而不是人类碰巧使用工具所进化的副产品。

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.
实际上，很可能人手的抓取功能是为了适应拳头的几何结构而进化过来的，而不是抓取功能的副产品。

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.
这就说明了，在很长一段时间里，物种之间的差异是根据使用手的不同方式开始，一些使用双手制造物品、一些利用拳头自我保护或者使用武力抢夺前者所制造的物品。