OCR Text |
Show 220 SELECTION. CHAP. XX. as they now are in those parts for which they are valned and cultivated. With animals we see something of the same kind; but they have not been domesticated in sufficient number or yielded sufficient varieties for a fair comparison. Sheep are valued for their wool, and the wool differs much more in the several races than the hair in cattle. Neither sheep, goats, European cattle, nor pigs are valued for their fleetness or strength; and we do not possess breeds differing in these respects like the race-horse and dray-horse. But fleetness and strength are valued in camels and dogs; and we have with the former the swift dromedary and heavy camel; with the latter the greyhound and mastiff. But dogs are valued even in a higher degree for their mental qualities and senses; and every one knows bow greatly the races differ in these respects. On the other hand, where the dog is valued solely to serve for food, as in the Polynesian islands and China, it is described as an extremely stupid animal.89 Blumenbach remarks that "many dogs, such as the badger" dog, have a build so marked and so appropriate for particular "purposes, that I should find it very difficult to persuade myself "that this astonishing figure was an accidental consequence of " degeneration." 90 But had Blumenbach reflected on the great principle of selection, he would not have used the term degeneration, and he would not have been astonished that dogs and other animals should become excellently adapted for the service of man. On the whole we may conclude that whatever part or cha~ racter is most valued-whether the leaves, stems, tubers, bulbs, flowers, fruit, or seed of plants, or the size, strength, fleetness, hairy covering, or intellect of animals-that character will almost invariably be found to present the greatest amount of difference both in kind and degree. And this result may be safely attributed to man having preserved during a long course of generations the variations which were useful to him, and neglected the others. I will conclude this chapter by some remarks on an important subject. With animals such as the giraffe, of which 89 Godron, • De l'Espece,' tom. ii. p. 27. 90 'The Anthropological Treatises of Blumenbach,' 1865, p. 292. CHAP. XX. SELECTION. 221 the whole structure is admirably co-ordinated for certain purposes, it has been supposed that all the parts must have been simultaneously modified; and it has been argued that, on the principle of natural selection, this is scarcely possible. But in thus arguing, it has been tacitly assumed that the variations must have been abrupt and great. No doubt, if the neck of a ruminant were suddenly to become greatly elongated, the fore limbs and back would have to be simultaneously strengthened and modified; but it cannot be denied that an animal might have its neck, or head, or tongue, or fore-limbs elongated a very little without any corresponding modification in other parts of the body ; and animals thus slightly modified would, during a dearth, have a slight advantage, and be enabled to browse on higher twigs, and thus survive. A few mouthfuls more or less every day would make all the difference between life and death. By the repetition of the same process, and by the occasional intercrossing of the survivors, there would be some progress, slow and fluctuating though it would be, towards the admirably co-ordinated structure of the giraffe. If the short-faced tumbler-pigeon, with its small conical beak, globular head, rounded body, short wings, and small feet-characters which appear all in harmony-had been a natural species, its whole structure would have been vie~ved as well fitted for its life ; but in this case we know that inexperienced breeders are urged to attend to point after point, and not to attempt improving the whole structure at the same time. Look at the greyhound, that perfect image of grace, symmetry, and vigour; no natural species can boast of a more admirably co-ordinated structure, with its tapering bead, slim body, deep chest, tucked-up abdomen, rat-like tail, and long muscular limbs, all adapted for extreme fleetness, and for running down weak prey. Now, from what we see of the variability of animals, and from what we know of the _method which different men follow in improving their stock-some chiefly attending to one point, others to another point, others again correcting defects by crosses, and so forth-we may feel assured that if we could see the long line of ancestors of a first-rate greyhound, up to its wild wolf-like progenitor, we should behold an infinite number of the finest gradations, sometimes in one character and sometimes in another, but all leading towards our |