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|OriginOfSpecies - 475 Rows|
|14 - Recapitulation and Conclusion||14-05 - Effects of its adoption on the study of Natural history||30||
A new variety raised by man will be a far more important and interesting subject for study than one more species added to the infinitude of already recorded species.
Our classifications will come to be, as far as they can be so made, genealogies; and will then truly give what may be called the plan of creation.
The rules for classifying will no doubt become simpler when we have a definite object in view.
We possess no pedigrees or armorial bearings; and we have to discover and trace the many diverging lines of descent in our natural genealogies, by characters of any kind which have long been inherited.
Rudimentary organs will speak infallibly with respect to the nature of long-lost structures.
Species and groups of species, which are called aberrant, and which may fancifully be called living fossils, will aid us in forming a picture of the ancient forms of life.
|14 - Recapitulation and Conclusion||14-02 - Recapitulation of the general and special circumstances in its favour||40||
If then we have under nature variability and a powerful agent always ready to act and select, why should we doubt that variations in any way useful to beings, under their excessively complex relations of life, would be preserved, accumulated, and inherited?
Why, if man can by patience select variations most useful to himself, should nature fail in selecting variations useful, under changing conditions of life, to her living products?
What limit can be put to this power, acting during long ages and rigidly scrutinising the whole constitution, structure, and habits of each creature, -- favouring the good and rejecting the bad?
I can see no limit to this power, in slowly and beautifully adapting each form to the most complex relations of life.
The theory of natural selection, even if we looked no further than this, seems to me to be in itself probable.
|14 - Recapitulation and Conclusion||14-01 - Recapitulation of the difficulties on the theory of Natural Selection||40||
Turning to geographical distribution, the difficulties encountered on the theory of descent with modification are grave enough.
All the individuals of the same species, and all the species of the same genus, or even higher group, must have descended from common parents; and therefore, in however distant and isolated parts of the world they are now found, they must in the course of successive generations have passed from some one part to the others.
We are often wholly unable even to conjecture how this could have been effected.
Yet, as we have reason to believe that some species have retained the same specific form for very long periods, enormously long as measured by years, too much stress ought not to be laid on the occasional wide diffusion of the same species; for during very long periods of time there will always be a good chance for wide migration by many means.
A broken or interrupted range may often be accounted for by the extinction of the species in the intermediate regions.
It cannot be denied that we are as yet very ignorant of the full extent of the various climatal and geographical changes which have affected the earth during modern periods; and such changes will obviously have greatly facilitated migration.
As an example, I have attempted to show how potent has been the influence of the Glacial period on the distribution both of the same and of representative species throughout the world.
We are as yet profoundly ignorant of the many occasional means of transport.
With respect to distinct species of the same genus inhabiting very distant and isolated regions, as the process of modification has necessarily been slow, all the means of migration will have been possible during a very long period; and consequently the difficulty of the wide diffusion of species of the same genus is in some degree lessened.
|14 - Recapitulation and Conclusion||14-02 - Recapitulation of the general and special circumstances in its favour||80||
But on the view of each species constantly trying to increase in number, with natural selection always ready to adapt the slowly varying descendants of each to any unoccupied or ill-occupied place in nature, these facts cease to be strange, or perhaps might even have been anticipated.
As natural selection acts by competition, it adapts the inhabitants of each country only in relation to the degree of perfection of their associates; so that we need feel no surprise at the inhabitants of any one country, although on the ordinary view supposed to have been specially created and adapted for that country, being beaten and supplanted by the naturalised productions from another land.
Nor ought we to marvel if all the contrivances in nature be not, as far as we can judge, absolutely perfect; and if some of them be abhorrent to our ideas of fitness.
We need not marvel at the sting of the bee causing the bee's own death; at drones being produced in such vast numbers for one single act, and being then slaughtered by their sterile sisters; at the astonishing waste of pollen by our fir-trees; at the instinctive hatred of the queen bee for her own fertile daughters; at ichneumonidae feeding within the live bodies of caterpillars; and at other such cases.