自然段A

Bats have a problem: how to find their way around in the dark. They hunt at night, and cannot use light to help them find prey and avoid obstacles. You might say that this is a problem of their own making, one that they could avoid simply by changing their habits and hunting by day. But the daytime economy is already heavily exploited by other creatures such as birds. Given that there is a living to be made at night, and given that alternative daytime trades are thoroughly occupied, natural selection has favoured bats that make a go of the night-hunting trade. It is probable that the nocturnal trades go way back in the ancestry of all mammals. In the time when the dinosaurs dominated the daytime economy, our mammalian ancestors probably only managed to survive at all because they found ways of scraping a living at night. Only after the mysterious mass extinction of the dinosaurs about 65 million years ago were our ancestors able to emerge into the daylight in any substantial numbers.

自然段A

蝙蝠面临一个问题：如何在黑暗中找到路。它们在夜间捕食，无法利用光线来帮助它们寻找猎物和避开障碍物。你可能会说，这是它们自己制造的问题，只要改变习性，白天捕食就能避免这个问题。但白天的经济已经被其他生物（如鸟类）充分利用。考虑到夜间捕猎可以谋生，而白天的其他行业已经被占据，自然选择偏爱那些在夜间捕猎上有所作为的蝙蝠。很可能夜间的生活方式在所有哺乳动物的祖先中已经存在很久了。在恐龙主导白天经济的那个时代，我们的哺乳动物祖先可能只能夜间勉强维持生计。直到大约6500万年前恐龙神秘地大规模灭绝后，我们的祖先才能够大量涌现到白天。

自然段B

Bats have an engineering problem: how to find their way and find their prey in the absence of light. Bats are not the only creatures to face this difficulty today. Obviously the night-flying insects that they prey on must find their way about somehow. Deep-sea fish and whales have little or no light by day or by night. Fish and dolphins that live in extremely muddy water cannot see because, although there is light, it is obstructed and scattered by the dirt in the water. Plenty of other modern animals make their living in conditions where seeing is difficult or impossible.

自然段B

蝙蝠面临的是一个工程问题：在没有光线的情况下如何找到路并找到猎物。蝙蝠并不是唯一面临这个困难的动物。显然，它们捕食的夜间飞行昆虫必须以某种方式找到路。深海鱼和鲸鱼白天或夜晚几乎没有光线。生活在极其浑浊水域的鱼类和海豚无法看见，因为虽然有光线，但被水中的污垢阻挡和散射。还有其他许多现代动物生活在视觉困难甚至不可能看见的环境中。

自然段C

Given the questions of how to manoeuvre in the dark, what solutions might an engineer consider? The first one that might occur to him is to manufacture light, to use a lantern or a searchlight. Fireflies and some fish (usually with the help of bacteria) have the power to manufacture their own light, but the process seems to consume a large amount of energy. Fireflies use their light for attracting mates. This doesn’t require a prohibitive amount of energy: a male’s tiny pinprick of light can be seen by a female from some distance on a dark night, since her eyes are exposed directly to the light source itself. However, using light to find one’s own way around requires vastly more energy, since the eyes have to detect the tiny fraction of the light that bounces off each part of the scene. The light source must therefore be immensely brighter if it is to be used as a headlight to illuminate the path, than if it is to be used as a signal to others. In any event, whether or not the reason is the energy expense, it seems to be the case that, with the possible exception of some weird deep-sea fish, no animal apart from man uses manufactured light to find its way about.

自然段C

考虑到在黑暗中如何操纵，工程师可以考虑什么解决方案？他可能首先想到的是制造光，使用灯笼或探照灯。萤火虫和一些鱼类（通常借助细菌）具有制造自己光的能力，但这个过程似乎消耗大量能量。萤火虫利用它们的光来吸引配偶。这并不需要过多的能量：雄性蟋蟀微小的光点在黑夜中可以被雌性蟋蟀从远处看见，因为她的眼睛直接暴露在光源上。然而，使用光来找到自己的路需要更多的能量，因为眼睛必须检测到反射在场景的每个部分上的微小光线。因此，如果要将光用作车灯照亮道路，它的光源必须要非常明亮，而不仅仅是用作信号给其他动物。无论因为什么原因（可能是能量消耗），除了一些奇怪的深海鱼类之外，似乎没有其他动物利用制造的光来找到自己的路。

自然段D

What else might the engineer think of? well, blind humans sometimes seem to have an uncanny sense of obstacles in their path. It has been given the name ‘facial vision’, because blind people have reported that it feels a bit like the sense of touch, on the face. One report tells of a totally blind boy who could ride his tricycle at good speed round the block near his home, using facial vision. Experiments showed that, in fact, facial vision is nothing to do with touch or the front of the face, although the sensation may be referred to the front of the face, like the referred pain in a phantom limb. The sensation of facial vision, it turns out, really goes in through the ears. Blind people, without even being aware of the fact, are actually using echoes of their own footsteps and of other sounds, to sense the presence of obstacles. Before this was discovered, engineers had already built instruments to exploit the principle, for example to measure the depth of the sea under a ship. After this technique had been invented, it was only a matter of time before weapons designers adapted it for the detection of submarines. Both sides in the Second world war relied heavily on these devices, under such codenames as Asdic (British) and Sonar (American), as well as Radar (American) or RDF (British), which uses radio echoes rather than sound echoes.

自然段D

工程师还能想到什么呢？盲人有时似乎能够神奇地感知到路径上的障碍物。这被称为“面部视觉”，因为盲人报告说它感觉有点像触觉在脸上。有一个报道讲述了一个完全失明的男孩如何能够在家附近的街区快速骑着三轮车，使用面部视觉。实验证明，事实上，面部视觉与触摸或面部前部无关，尽管感觉可能会被引导到面部前部，就像幻肢疼痛一样。事实证明，面部视觉的感觉实际上通过耳朵进入。盲人甚至没有意识到这个事实，实际上是利用了自己脚步声和其他声音的回声来感知障碍物的存在。在此被发现之前，工程师已经构建了利用这一原理的仪器，例如测量船下海洋深度的仪器。在这项技术被发明后不久，武器设计师将其用于潜艇探测只是时间问题。二战中的双方都大量依赖这些装置，其中英国的代号为Asdic，美国的为Sonar，还有美国的Radar或英国的RDF，它使用的是无线电回波而不是声波回波。

自然段E

The Sonar and Radar pioneers didn’t know it then, but all the world now knows that bats, or rather natural selection working on bats, had perfected the system tens of millions of years earlier, and their ‘radar’ achieves feats of detection and navigation that would strike an engineer dumb with admiration. It is technically incorrect to talk about bat ‘radar’, since they do not use radio waves. It is sonar. But the underlying mathematical theories of radar and sonar are very similar, and much of our scientific understanding of the details of what bats are doing has come from applying radar theory to them. The American zoologist Donald Griffin, who was largely responsible for the discovery of sonar in bats, coined the term ‘echolocation’ to cover both sonar and radar, whether used by animals or by human instruments.

自然段E

当时的声纳和雷达先驱者并不知道，但现在全世界都知道，蝙蝠或者说自然选择对蝙蝠的作用，早在数千万年前就完善了这一系统，它们的“雷达”实现了在工程师眼中令人惊叹的探测和导航功能。技术上讲，称之为蝙蝠的“雷达”是不正确的，因为它们不使用无线电波，而是声纳。但雷达和声纳的基本数学理论非常相似，我们对蝙蝠行为的科学理解大部分来源于将雷达理论应用于它们身上。美国动物学家唐纳德·格里芬（Donald Griffin）在发现蝙蝠的声纳方面起到了重要作用，并创造了“回声定位”这个术语，它包括动物或人类仪器使用的声纳和雷达。