本文节选自达尔文的《物种起源》，翻译者是苗德岁，在《物种起源》众多的中译本中，我认为苗翻译得最好。
I have now restated the chief facts and considerations which have thoroughly convinced me that species have been modified, during a long course of descent, by the preservation or the natural selection of many successive slight favourable variations. I cannot believe that a false theory would explain, as it seems to me that the theory of natural selection does explain, the several large classes of facts above specified. I see no good reason why the views given in this volume should shock the religious feelings of any one. A celebrated author and divine has written to me that “he has gradually learnt to see that it is just as noble a conception of the God to believe that He created a few original forms capable of self-development into other and needful forms, as to believe that He required a fresh act of creation to supply the voids caused by the action of His laws.”
现在我业已复述了一些主要的事实与思考，这些已令我完全相信，物种在长期的世系传衍的过程中，通过保存或自然选择很多连续轻微有利的变异，业已发生了变化。我不能相信，一种谬误的理论，何以能够解释以上特别陈述的几大类事实，而在我看来，自然选择理论确实解释了这些事实。至于本书所提出的观点何以震撼了任何人的宗教情感，我却看不出任何合适的理由。一位著名的作者兼神学家致信与我说，“他已逐渐地搞清，相信‘上帝’创造出了能自行发展成为其他所需类型的少数几个原始类型，这与相信‘上帝’需要用从头开始的造物行为去充填‘上帝’法则作用所造成的虚空，同样都是尊崇‘神性’的理念”。
Why, it may be asked, have all the most eminent living naturalists and geologists rejected this view of the mutability of species? It cannot be asserted that organic beings in a state of nature are subject to no variation; it cannot be proved that the amount of variation in the course of long ages is a limited quantity; no clear distinction has been, or can be, drawn between species and well-marked varieties. It cannot be maintained that species when intercrossed are invariably sterile, and varieties invariably fertile; or that sterility is a special endowment and sign of creation. The belief that species were immutable productions was almost unavoidable as long as the history of the world was thought to be of short duration; and now that we have acquired some idea of the lapse of time, we are too apt to assume, without proof, that the geological record is so perfect that it would have afforded us plain evidence of the mutation of species, if they had undergone mutation.
也许有人会问，为什么所有健在的最为卓越的博物学家与地质学家们都反对物种可变性这一观点呢？不能断言生物在自然状态下不会发生变异；不能证明变异量在漫长岁月的过程中是有限的；在物种与特征显著的变种之间没有或不能划出泾渭分明的界限。不能坚持认为物种杂交时一成不变地皆是不育的，而变种杂交时则一成不变地皆是能育的；或者坚持认为不育性是一种特殊天授与造物的标志。只要把世界的历史视为是短暂的，几乎难免地就得相信物种是不变的产物；而现在我们既然对于逝去的时间已经获得了某种概念，我们便会毫无根据地、过于轻易地假定地质记录是如此完整，以至于物种若是经历过变异的话，地质记录即会向我们提供物种变异的明显证据。
But the chief cause of our natural unwillingness to admit that one species has given birth to other and distinct species, is that we are always slow in admitting any great change of which we do not see the intermediate steps. The difficulty is the same as that felt by so many geologists, when Lyell first insisted that long lines of inland cliffs had been formed, and great valleys excavated, by the slow action of the coast-waves. The mind cannot possibly grasp the full meaning of the term of a hundred million years; it cannot add up and perceive the full effects of many slight variations, accumulated during an almost infinite number of generations.
我们之所以很自然地不甘承认一个物种会产生其他不同物种的主要原因，乃在于我们若是看不到任何巨大变化的一些中间步骤的话，我们总是不会很快承认这一变化的。当莱尔最初主张长排的内陆峭壁的形成以及巨大山谷的凹陷都是海岸波浪缓慢冲蚀所致时，当时的很多地质学家们对此均难以承认，其感受正像上述情形一样。即令对一亿年这个词，人们的思想也不可能领会其全部意义；而对于在几乎无限的世代中所累积起来的很多轻微变异，其全部效果则更加难以综合与领悟了。