达尔文进化论

Charles Darwin and His Theory of Evolution

J﹒G﹒Crowther

During the voyage of the Beagle, Darwin had been deeply impressed by similarities between existing South American animals and the fossil remains. He had noted how closely similar animals replaced one another when proceeding southward. He was struck by the South American character of the animals on the Galapagos archipelago, differing from island to island, and yet all the islands were recent and of the same age. It seemed utterly improbable that all of these myriad different yet similar species could each have been individually created. He felt that they could only be explained by supposing that they had sprung from a few original species which had gradually become modified. The subject haunted him.

Though Darwin said that he started collecting facts on origin of Species without the guidance of any theory, his first notebook on the subject shows that he was in fact grappling with the problem of a scientific law which would explain how these modifications occurred. His mind went out to the law of gravitation. Before Newton, men had thought that each planet was individually kept in its course by God. There was no necessary relation between all of the moving bodies. In 1837, men believed that each individual species of animal was created by God, without necessary relation with any other species.

But would it not be much more simple and sublime to suppose that after the creation of original animals, all their multifarious successions should arise from them by the operation of some fixed scientific law? This was one of the first ideas, a law which would do for biology what gravitation had done for astronomy.

But what was the law? He tried to think it out, and almost succeeded. He noted that a variety of South American ostrich might have not been ‘well adapted, and thus perish ’, while in a variety with favourable qualities ‘ many might be produced ’. this required the principle that some variations survive because they are adapted to changing circumstances and that the

‘death of species is a consequence of non –adaptation to circumstances’ .

Darwin had almost worked out the idea of natural selection and the survival of the fittest, but they did not become quite clear to him until the following year, 1838, when he happened to read Malthus’Essay on the principle of population. Malthus said that ‘population, when unchecked, increases in a geometrical ratio…This implies a strong and constantly operating check on population from the difficulty of subsistence…’

Darwin saw at once that ‘ under these circumstance ’ favourable variations would tend to be preserved and unfavourable ones to be destroyed. The result of this would be the formation of a new species. Here then I had a theory by which to work.

Darwin established the evolutionary method by using it to explain the origin of species. But he also showed how to use it in many other directions. In his descent of man he showed how it could be applied in anthropology, and in The Expression of the Emotions in man and animals, to psychology.

By showing that one species must have arisen from another, he raised the question of how, and thus founded the science of genetics. He explored this science in his Variations of Animals and Plants under Domestication, and said that ‘ a grand and almost untrodden field of inquiry will be opened, on the cause and law of variation, on correlation, on the effects of use and disuse, on the direct action of external conditions, and so on…’

He threw out scores of ideas which have contained profound truths, even in some of his most criticized conceptions, such as Pangenesis. In this he ascribed the mechanism of heredity to physical entities which he called gemmules, supposed to connected with every part of body. The modern knowledge of genes and hormones has confirmed his fundamental idea.

He buttressed his technical position with huge monographs on barnacles, and important works on coral reefs, the fertilization of flowers by insects, climbing and movement in plants, crossing, and a big final volume on The Formation of vegetable mould, through the Action of

Worms, published in the year before he died.

His range of enquiry was astonishing, and his power of drawing important conclusions from inconspicuous details unequalled. Nevertheless, time has, of course, emphasized many of the obscurities of which he was himself very much aware. While the fact of evolution became obvious, its inner mechanism, in spite of all the biological research of the last hundred years, is still under sharp dispute.

Why did Darwin’s work have such an effect, not only on science, but on the whole of human thought? It was because it contained principles which were of interest to many different classes in society.

[ 806 words ]

译文：

查尔斯﹒达尔文进化论

J﹒G﹒克劳瑟

在小猎犬号的航程中，达尔文对南美洲的动物与动物化石之间的相似性留下了深刻印象。他注意到，一路往南，种类极为相似的动物相互取代。加拉帕格斯群岛上南美洲动物的特性因岛屿而异，但所有的岛屿都是在较近的同一时期形成的，这令他大为吃惊。要说所有这许多不同却相似的物种是一个单独创造出来的，这似乎根本不可能。他认为唯一的解释与假设他们源于几个最初物种，而后在逐渐变化而成。这一问题始终萦绕在他心头。

达尔文说自己开始为《物种起源》收集论据时没有任何理论指导，但他就此所作的第一本笔记却表明实际上他是在努力探索一种解释，这些变异如何产生的科学规律。他想到的是万有引力定律。在牛顿之前，人们认为每一颗行星有上帝规定了各自运行轨迹。所有运动物体之间没有必然联系。在1837年，人们认为动物的每

一种物种都是上帝创造的，物种之间没有必然的联系。

那么假设最初的动物创造出来后，他们所有的各种演替都由于某种固定不变的科学规律的作用而产生，岂不更简便，更好？这是他最初的设想之一，一种万有引力定律之适用生物学的普遍定律。

可那究竟是什么定律呢？他努力推究，几乎获得成功。他注意到，一种南美鸵鸟可能没能“很好适应，因此消失，”而在具有有利特性的品种身上“也许会产生多种变种。”这就需要一种原理，及某些变异物种幸存是因为适应了变化的环境。“而物种的死亡是对环境不适应的结果。”

达尔文几乎提出了自然选择与适者生存理论，但直到次年，即1838年，这些想法才开始变得明朗，当时他正好再读马尔萨斯的《人口论》。马尔萨斯指出“人口不受抑制时以几何数增长。这意味着维持生计之艰难对人口所起的强有力的，长期的抑制作用。”

达尔文确立了进化论，用以解释物种起源。但他也展示了怎样进化的问题，由此建立了遗传学。他在《动物和植物在家养下的变异》中探讨了遗传学理论，指出“一个广博的尚无人涉足的研究领域将得到开辟，这一领域将涉及变异起因与规律，相互关系，运用废弃的结果，外部条件的直接作用，等等。”

他提出许多含有深刻哲理的想法，就连泛生论等广受批评的一些看法也是如此。在泛生论中他把遗传的机理归于他叫作“小芽”的身体实体，而这些实体被认为与身体的各个部分都有联系，现代有关基因和荷尔蒙的知识已经证实了他的基本观点。

他写下了有关甲壳动物的大量有关专著，有关珊瑚礁的、昆虫为花受精的、植物攀援长势以及杂交的重要著作，以及去世前出版最后一大卷：《蚯蚓作用下植物土壤的形成》都为专业假设提供依据。

他探索范围之广令人惊讶，他从不引人注目的细节中得出重要结论的能力无与伦比，不过，随着时间的推移，人们往往更多地强调他理论中的许多模糊不清之处，

其实这些模糊的地方他本人当时也是清楚的意识到了的。虽然进化的事实显而易见，尽管过去的一百年来，进行大量的生物研究，但对其运行的内在机制，人们仍有激烈争论之中。

为什么达尔文的研究不仅对科学，而且对整个人类思想具有这么大的影响？因为他包含了社会上许多不同阶层普遍感兴趣的原理。