Natural Selection is Pure Common-Sense
What is this Natural Selection which has been dead for half a century, but which Mr. Belloc still exerts himself industriously through four long papers to kill all over again? It is the purest common-sense, the most obvious deduction from obvious facts. I have set out the idea as plainly as I could in the Outline of History Mr. Belloc is attacking. It is put so plainly there that, before he can begin to argue against it, he has to misstate it; he has to tell the story all over again in his own words and get it suitably askew. It was quite open to him to quote from my account, but he preferred to compile his own misstatement. Indeed, in all this argument against Natural Selection he never once quotes my actual words. He paraphrases throughout. He has put some words between inverted commas in one place, so as inadvertently to produce the impression that they are mine, but they are not mine.
Now the facts upon which the idea of Natural Selection rests are matters of universal knowledge. “Every species of living thing is continually dying and being born again as a multitude of fresh individuals”; that is the primary fact. No species seems to be perfectly adapted to its conditions, and even the happiest species tends to multiply until it is in a state of need and pressure. So far surely we are dealing with things beyond dispute. And next comes the fact of individuality. Every living unit is individual with a difference of its own. Every individual has its own distinctive differences, and each of these differences may or may not be an advantage or a disadvantage. Individuals with advantageous differences will generally get on better in life, prosper and so be able to breed more freely, than those with disadvantageous differences. Offspring have a tendency to repeat the distinctive differences of their parents. Therefore, taking a species as a whole by the million or billion or million billion—for few species of animals or plants are represented by fewer individuals than a million—there will be in each successive generation a greater number of individuals with the differences that are advantageous relative to the number with disadvantages. In other words, the average of the species will have moved more or less in the direction of the advantageous differences, whatever they may be, and however numerous they may be. If, for example, the species is chased and has to climb or run for it, there will be rather more good climbers and sprinters in the new generation. There may be other dangers and other needs; they will not affect the premium set on quickness and the fate of the slow. And if the circumstances of the species continue to press in the same direction, the movement of the average will be in the same direction in this respect for so long as they continue to press. Over a few score or even a few hundred generations, and under conditions not very strenuous, a species may not change very much. It may seem to be fixed in its general characteristics, just as the continents seem to be fixed in their general outline. But, as the range of time extends and the pressure of necessity continues, the change becomes more striking.