生物学
1859
物种起源
生命的浩瀚多样，源自共同祖先，经由自然选择这把缓慢的筛子塑造而成。
Choose your version
生物彼此有差异，而那些恰好最适应自己世界的，会留下最多的后代——让它持续几百万年，你便得到整棵生命之树。
核心想法
在任何一群动植物中，没有两个个体是完全相同的，而其中一些差异会传给后代。由于产下的幼体远多于能够存活的数目，对食物、空间和安全，存在着一场无声而持续的较量。那些性状稍稍更适应环境的个体，往往活得更久、繁殖得更多——并把这些有用的性状传下去。达尔文把这把筛子，称作自然选择。
让它运转成千上万代，微小的变化便累积成深刻的改变。一个种群可以渐渐变成一个新物种；一个祖先形态可以分枝成许多种。沿着每一根枝条往回追溯得足够远，它们终将相遇——地球上所有的生命都彼此相关，就像同一棵参天大树上的细枝。
它是如何诞生的
年轻的博物学家达尔文，曾搭乘「小猎犬号」环球航行近五年，一路所见的生物——尤其是在加拉帕戈斯群岛，每座岛上都有同一主题的不同变奏——在他心里埋下了一颗怀疑的种子：物种或许并非固定不变、各自被创造。回到家中，他又用了二十多年，默默积累证据、饲养鸽子、与各地博物学家通信，迟迟不愿发表这个过于惊世骇俗的想法。
1858 年，一封来自阿尔弗雷德·拉塞尔·华莱士的信逼得他不得不动——华莱士独立地想到了完全相同的机制。二人的工作被联合发表，而 1859 年，达尔文出版了《物种起源》。首印当天即告售罄；这套论证所重塑的，不仅是生物学，更是人类对自身在自然中位置的理解。
它为何重要
在达尔文之前，生命那令人眼花缭乱的多样性，通常被解释为固定不变、各自被设计出来的。而他表明，这一切其实可以源自一个单一的、盲目的、自然的过程，在极其漫长的时间里运作——并且，含蓄却无可辩驳地指出：人类只是这同一棵大树上的一根枝条，而非置身其外。这是人类有史以来最具影响力的想法之一。
一个可以想象的画面
想象一位育种者，挑选让哪些狗或鸽子交配，一代代地慢慢把某个性状放大，直到一头狼的后代变成一只吉娃娃。达尔文的洞见是：大自然做的正是这件事——只不过那位「育种者」，不过是环境本身，它只是悄悄地让更适应的个体留下更多后代。没有谁在挑选；那「挑选」，只是存活自己做的事，而它所用的时间，远比任何育种者拥有的都要长。
它的位置
《物种起源》问世几年后，一位默默无闻的修士格雷戈尔·孟德尔，弄清了性状究竟是如何传递的——以一个个离散的单位，也就是我们今天所说的基因——但他的工作被冷落了数十年。当它被重新发现时，恰好补上了达尔文的理论一直缺失的那块遗传拼图，两个想法于是融合成了现代演化生物学——它正是从疫苗到濒危物种保育、背后的那套框架。
Original source text
引言
When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts seemed to me to throw some light on the origin of species — that mystery of mysteries, as it has been called by one of our greatest philosophers.
In considering the Origin of Species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, on their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that each species had not been independently created, but had descended, like varieties, from other species.
I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species. … Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification.
生存竞争
A struggle for existence inevitably follows from the high rate at which all organic beings tend to increase. Every being, which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occasional year, otherwise, on the principle of geometrical increase, its numbers would quickly become so inordinately great that no country could support the product.
It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage.
As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected.
自然选择
Can it, then, be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind?
This preservation of favourable variations and the rejection of injurious variations, I call Natural Selection. Variations neither useful nor injurious would not be affected by natural selection, and would be left a fluctuating element.
It may be said that natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being.
理论的难点
To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.
Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; … then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real.
复述与结论
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us.
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
Down, Kent · 1859