段落A

Our life span is restricted. Everyone accepts this as ‘biologically’ obvious. ‘Nothing lives for ever!’ However, in this statement we think of artificially produced, technical objects, products which are subjected to natural wear and tear during use. This leads to the result that at some time or other the object stops working and is unusable (‘death’ in the biological sense). But are the wear and tear and loss of function of technical objects and the death of living organisms really similar or comparable?

段落A：我们的寿命是受限的。每个人都认为这是“生物学上”显而易见的。“没有什么东西能永远活下去！”然而，在这个说法中，我们思考的是人工制造的、技术性的物体，这些产品在使用过程中受到自然磨损。这导致某个时候物体停止工作，无法继续使用（在生物学意义上，即“死亡”）。但是技术物体的磨损和功能丧失与生物有机体的衰老和死亡真的相似或可比吗？

段落B

Our ‘dead’ products are ‘static’, closed systems. It is always the basic material which constitutes the object and which, in the natural course of things, is worn down and becomes ‘older’. Ageing in this case must occur according to the laws of physical chemistry and of thermodynamics. Although the same law holds for a living organism, the result of this law is not inexorable in the same way. At least as long as a biological system has the ability to renew itself it could actually become older without ageing; an organism is an open, dynamic system through which new material continuously flows. Destruction of old material and formation of new material are thus in permanent dynamic equilibrium. The material of which the organism is formed changes continuously. Thus our bodies continuously exchange old substance for new, just like a spring which more or less maintains its form and movement, but in which the water molecules are always different.

段落B：我们的“死亡”产品是“静态”的、封闭的系统。它们始终是由构成物体的基础材料组成，并且在自然的发展过程中会磨损和变老。在这种情况下，衰老必须遵循物理化学和热力学的定律。虽然对于生物有机体也适用同样的定律，但这一定律的结果并不像技术物体那样无法逆转。至少只要生物系统具有自我更新的能力，它实际上可以在不衰老的情况下变老；有机体是一个开放的、动态的系统，其中新的物质不断流动。旧物质的破坏和新物质的形成处于永久的动态平衡状态。有机体的构成物质不断变化。因此，我们的身体不断以旧物质与新物质进行交换，就像一个弹簧，它基本上保持其形态和运动，但其中的水分子始终是不同的。

段落C

Thus ageing and death should not be seen as inevitable, particularly as the organism possesses many mechanisms for repair. It is not, in principle, necessary for a biological system to age and die. Nevertheless, a restricted life span, ageing, and then death are basic characteristics of life. The reason for this is easy to recognise: in nature, the existent organisms either adapt or are regularly replaced by new types. Because of changes in the genetic material (mutations) these have new characteristics and in the course of their individual lives they are tested for optimal or better adaptation to the environmental conditions. Immortality would disturb this system – it needs room for new and better life. This is the basic problem of evolution.

段落C：因此，衰老和死亡不应被视为不可避免，特别是因为有机体具有许多修复机制。从原则上讲，生物系统并不需要衰老和死亡。然而，有限的寿命、衰老和死亡却是生命的基本特征。这个原因很容易理解：在自然界中，已经存在的有机体要么适应环境，要么定期被新类型取代。由于基因物质的变化（突变），新类型具有新的特征，并且在其个体生命的过程中会被测试其对环境条件的最佳或更好的适应性。永生将打破这个系统——它需要空间来容纳新的、更好的生命。这是进化的基本问题。

段落D

Every organism has a life span which is highly characteristic. There are striking differences in life span between different species, but within one species the parameter is relatively constant. For example, the average duration of human life has hardly changed in thousands of years. Although more and more people attain an advanced age as a result of developments in medical care and better nutrition, the characteristic upper limit for most remains 80 years. A further argument against the simple wear and tear theory is the observation that the time within which organisms age lies between a few days (even a few hours for unicellular organisms) and several thousand years, as with mammoth trees.

段落D：每个有机体都有一个高度特征化的寿命。不同物种的寿命存在显著差异，但在一个物种内部，这个参数相对稳定。例如，人类寿命的平均持续时间在数千年间几乎没有变化。尽管由于医疗保健和更好的营养，越来越多的人达到了高龄，但对大多数人来说，特征性的寿命上限仍然是80岁。对简单的磨损理论的另一个反驳是观察到有机体衰老的时间范围介于几天（对于单细胞生物甚至几小时）到几千年之间，如长毛树。

段落E

If a life span is a genetically determined biological characteristic, it is logically necessary to propose the existence of an internal clock, which in some way measures and controls the ageing process and which finally determines death as the last step in a fixed programme. Like the life span, the metabolic rate has for different organisms a fixed mathematical relationship to the body mass. In comparison to the life span this relationship is ‘inverted’: the larger the organism the lower its metabolic rate. Again this relationship is valid not only for birds, but also, similarly on average within the systematic unit, for all other organisms (plants, animals, unicellular organisms).

段落E：如果寿命是一种基因决定的生物学特征，那么逻辑上就有必要提出内部时钟的存在，它以某种方式测量和控制衰老过程，并最终确定死亡作为固定程序中的最后一步。与寿命相比，代谢率与体重之间有着固定的数学关系。与寿命相比，这种关系是“倒置”的：生物体越大，其代谢率越低。这种关系不仅对鸟类有效，而且在同一系统单位内对所有其他生物（植物、动物、单细胞生物）也是如此。

段落F

Animals which behave ‘frugally’ with energy become particularly old, for example, crocodiles and tortoises. Parrots and birds of prey are often held chained up. Thus they are not able to ‘experience life’ and so they attain a high life span in captivity. Animals which save energy by hibernation or lethargy (e. g. bats or hedgehogs) live much longer than those which are always active. The metabolic rate of mice can be reduced by a very low consumption of food (hunger diet). They then may live twice as long as their well-fed comrades. Women become distinctly (about 10 per cent) older than men. If you examine the metabolic rates of the two sexes you establish that the higher male metabolic rate roughly accounts for the lower male life span. That means that they live life ‘energetically’ – more intensively, but not for as long.

段落F：那些节约能量的动物往往寿命更长，例如鳄鱼和乌龟。鹦鹉和猛禽经常被束缚起来。因此它们无法“体验生活”，所以在圈养状态下它们能够达到很高的寿命。冬眠或懒散（如蝙蝠或刺猬）可以延长生命，而总是活动的动物则不能。通过非常低的食物摄入（饥饿饮食），小鼠的代谢率可以降低。它们的寿命可能是其吃得饱的同类的两倍。女性明显比男性长寿（大约多10%）。如果你检查两性的代谢率，你会发现较高的男性代谢率大致解释了较低的男性寿命。这意味着他们以更“精力充沛”的方式生活——更加积极，但时间不长。

段落G

It follows from the above that sparing use of energy reserves should tend to extend life. Extreme high performance sports may lead to optimal cardiovascular performance, but they quite certainly do not prolong life. Relaxation lowers metabolic rate, as does adequate sleep and in general an equable and balanced personality. Each of us can develop his or her own ‘energy saving programme’ with a little self-observation, critical self-control and, above all, logical consistency. Experience will show that to live in this way not only increases the life span but is also very healthy. This final aspect should not be forgotten.