79 Population Growth
The growth of population during the past few centuries is no proof that population will continue to grow straight upward toward infinity and doom. On the contrary, demographic history offers evidence that population growth has not been at all constant. According to paleoecologist Edward Deevey, the past million years show three momentous changes. The first, a rapid increase in population around one m illion B. C., followed the innovations of tool making and tool using. But when the new power from the use of tools has been exploited, the rate of world population growth fell and became almost stable. The next rapid jump in population started perhaps 10,000 years ago, when mankind began to keep herds, plow and plant the earth. Once again when initial productivity gains had been absorbed, the rate of population growth abated. These two episodes suggest that the third great change, the present rapid growth, which began in the West between 250 and 350 years ago, may also slow down when, or if, technology begins to yield fewer innovations. Of course, the current knowledge revolution may continue without foreseeable end. Either way - contrary to popular belief in constant geometric growth - population can be expected in the long run to adjust to productivity. And when one takes this view, population growth is seen to represent economic progress and human triumph rather than social failure.
人口增长
以往几个世纪人口的增长并不能证明人口会无限地直线向上增长直到毁灭的 地步。 相反地，人口统计史料证明人口的增长完全不是稳定的。 古生态学家爱德华·狄维 认为，在过去 100 万年间出现过 3 次重大的变动。 第一次在公元前 100 万年左右，随着在 工具的制作和使用上的革新而出现人口迅速增长。 但当工具的使用所产生的新动力被充分 利用以后，世界人口增长率下降并且趋于稳定。 第二次人口剧增大约始于人类开始蓄畜、 垦耕的 10，000 年前。 一旦最初的生产力增长被吸收殆尽，人口的增长再次衰落。 以上两 段说明，若技术革新的成果开始减少，从 250 到 350 年前就在西方开始出现的并且目前还在 继续的人口迅速增长可能也会放慢。 当然，当前的知识革命也许会持续下去而无法预见其 末来。 无论如何，与那种认为人口以几何级数持续增长的观点相反，从长远的观点来说， 人口可望受到生产力的调节。 接受了这一观点，人口的增长就可以被看成是经济进步和人 类胜利的标志，而不是社会衰败的标志。
80 Evolution and Wheels
In the past, evolutionary biologists contemplating the absence of wheels in nature agreed that the explanation was not undesirability: wheels would be good for animals, just as they are for us. Animals were prevented from evolving wheels, the biologists reasoned, by the following dilemma: living cells in an animal's body are connected to the heart by blood vessels, and to the brain by nerves. Because a rotating joint is essential to a wheel, a wheel made of living cells would twist its artery vein and nerve connections at the first revolution, making living impracticable. However, there is a flaw in the argument that the evolution of wheeled animals was thwarted by the insoluble joint problem. The theory fails to explain why animals have not evolved wheels of dead tissue with no need for arteries and nerves. Countless animals, including us, bear external structures without blood supply or nerves - for example, our hair and fingernails, or the scales, claws, and ho rns of other animals. Why have rats not evolved bony wheels, similar to roller skates?Paws might be more useful than wheels in some situations, but cats' claws are retractable: why not retractable wheels?We thus arrive at the serious biological paradox flippantly termed the RRR dilemma: nature's failure to produce rats with retractable roller skates.
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