登陆注册
15712300000007

第7章

Who, for instance, has duly reflected upon all the consequences of the marvellous struggle for existence which is daily and hourly going on among living beings? Not only does every animal live at the expense of some other animal or plant, but the very plants are at war. The ground is full of seeds that cannot rise into seedlings; the seedlings rob one another of air, light and water, the strongest robber winning the day, and extinguishing his competitors. Year after year, the wild animals with which man never interferes are, on the average, neither more nor less numerous than they were; and yet we know that the annual produce of every pair is from one to perhaps a million young,--so that it is mathematically certain that, on the average, as many are killed by natural causes as are born every year, and those only escape which happen to be a little better fitted to resist destruction than those which die. The individuals of a species are like the crew of a foundered ship, and none but good swimmers have a chance of reaching the land.

Such being unquestionably the necessary conditions under which living creatures exist, Mr. Darwin discovers in them the instrument of natural selection. Suppose that in the midst of this incessant competition some individuals of a species (A) present accidental variations which happen to fit them a little better than their fellows for the struggle in which they are engaged, then the chances are in favour, not only of these individuals being better nourished than the others, but of their predominating over their fellows in other ways, and of having a better chance of leaving offspring, which will of course tend to reproduce the peculiarities of their parents. Their offspring will, by a parity of reasoning, tend to predominate over their contemporaries, and there being (suppose) no room for more than one species such as A, the weaker variety will eventually be destroyed by the new destructive influence which is thrown into the scale, and the stronger will take its place. Surrounding conditions remaining unchanged, the new variety (which we may call B)--supposed, for argument's sake, to be the best adapted for these conditions which can be got out of the original stock--will remain unchanged, all accidental deviations from the type becoming at once extinguished, as less fit for their post than B itself. The tendency of B to persist will grow with its persistence through successive generations, and it will acquire all the characters of a new species.

But, on the other hand, if the conditions of life change in any degree, however slight, B may no longer be that form which is best adapted to withstand their destructive, and profit by their sustaining, influence;in which case if it should give rise to a more competent variety (C), this will take its place and become a new species; and thus, by 'natural selection', the species B and C will be successively derived from A.

That this most ingenious hypothesis enables us to give a reason for many apparent anomalies in the distribution of living beings in time and space, and that it is not contradicted by the main phenomena of life and organization appear to us to be unquestionable; and so far it must be admitted to have an immense advantage over any of its predecessors.

But it is quite another matter to affirm absolutely either the truth or falsehood of Mr. Darwin's views at the present stage of the inquiry.

Goethe has an excellent aphorism defining that state of mind which he calls 'Thatige Skepsis'a--active doubt. It is doubt which so loves truth that it neither dares rest in doubting, nor extinguish itself by unjustified belief; and we commend this state of mind to students of species, with respect to Mr. Darwin's or any other hypothesis, as to their origin. The combined investigations of another 20 years may, perhaps, enable naturalists to say whether the modifying causes and the selective power, which Mr. Darwin has satisfactorily shown to exist in nature, are competent to produce all the effects he ascribes to them, or whether, on the other hand, he has been led to over-estimate the value of his principle of natural selection, as greatly as Lamarck overestimated his vera causa of modification by exercise.

But there is, at all events, one advantage possessed by the more recent writer over his predecessor. Mr. Darwin abhors mere speculation as nature abhors a vacuum. He is as greedy of cases and precedents as any constitutional lawyer, and all the principles he lays down are capable of being brought to the test of observation and experiment. The path he bids us follow professes to be, not a mere airy track, fabricated of ideal cobwebs, but a solid and broad bridge of facts. If it be so, it will carry us safely over many a chasm in our knowledge, and lead us to a region free from the snares of those fascinating but barren Virgins, the Final Causes, against whom a high authority has so justly warned us.

"My sons, dig in the vineyard," were the last words of the old man in the fable; and, though the sons found no treasure, they made their fortunes by the grapes.

End

同类推荐
  • Wessex Poems and Other Verses

    Wessex Poems and Other Verses

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 素问要旨论

    素问要旨论

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • The Importance of Being Earnest

    The Importance of Being Earnest

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 落花

    落花

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 回生集

    回生集

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
热门推荐
  • 史上最强高中生

    史上最强高中生

    从无限轮回世界归来,林杉只想过一点普通人的生活。但是美人如画,作为守护神的林杉当然是没那种希望啦~
  • 赤瞳火眼

    赤瞳火眼

    省医药公司的小小业务员杨树,一直苦逼奋斗,因为吃葡萄吃进去几条小蛆虫,导致身体异变。因此获得异能,一双赤褐色眼睛,异能能透视一切,能治病,也能杀人。异能为本,科技为先,兵王兄弟并肩热血,奇珍异宝岂容他人觊觎。或爆烈震慑宵小,或杀人于无形。人生巨变,财富的聚集变得简单,却让人不安。小富即安的心态,精神上的惫懒,使得他理想不高,可事情的发生往往不已个人意愿为准,他被身边的亲人和朋友推着向前。他能成为巨富,却改变不了猥琐的人生。想要静守本心,想要忠贞不渝,却抵不过俗世乱情。或强推,或被逆推,居然生养了九个子女。
  • 堕落谱

    堕落谱

    一个弑父累母的少年,一片血与泪汇聚的汪洋,当时钟敲响十二下,所有的灵魂都将堕落腐烂,世界将坠入永久的黑暗。母亲说:“活下去!”那么他便要活下去,即便痛苦,即便绝望。
  • TFBOYS勇敢爱

    TFBOYS勇敢爱

    就像天生注定一样。王源和夏小阳或许是注定的。历经波折。但是有情人终成眷属。不论之前发生了什么,他们都不计前嫌。
  • 镜天择

    镜天择

    天地不仁,以万物为刍狗。当方然杀出一条血路,回首前尘时,才恍然发现却原来天道有情。
  • 余生未央

    余生未央

    青春还没有来得及回味,就这么渐行渐远了。我多么想从走一遍,好好回味,不辜负当年的自己。人生真的很奇妙你以为的事最终没有实现不期待的事最终成为了现实这就是所谓人各天命自有定数吗?有些事情我是该主动出击还是随遇而安?
  • 我爱过你,没有然后

    我爱过你,没有然后

    二十岁生日那天,男朋友跟我姐姐在我卧室滚床单。我怒剪渣男不成,反而伤了小三的胸,自己也落得个胃切除的凄惨下场。渣男和小三想美美出国的愿望落空,小三把一切罪责推到我身上,而那个被我撞到的“贾宝玉”,居然想趁机吃我豆腐。是可忍孰不可忍,我对着他的裤裆就是一脚。谁知道骆安歌居然说他那方面出了问题,要我负责。而他要我负责的手段,竟是对我下药,完事后让渣男跟我同床。囚禁,疯狂的占有,我以为是爱,可是,背后的真相,令人唏嘘。一场爆炸,斩断了我们之间的一切爱恨。八年后,一切还回得去吗?
  • 伤寒辨要笺记

    伤寒辨要笺记

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 三年天下

    三年天下

    三年为限,她以婚约换天下,为他出谋划策,冲锋陷阵。三年后,他坐拥天下,锦绣万里,却觉得百尺朝堂不应成为鹰击长空的桎梏,狠心将她赶出了自己的世界。却不想她却成为自己心只所系……【情节虚构,请勿模仿】
  • 圣经学规纂论学

    圣经学规纂论学

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。