The human species

by A. de Quatrefages

Whoever has the smallest acquaintance with embryogenesis will have no difficulty in understanding that conditions of life act especially upon organisms in respect to their formation and evolution. However, their influence upon an animal, even when full-grown, is sometimes quite as marked. Our sheep, when transferred to America, generally become acclimatised without undergoing great changes. Their fleece, particularly, is retained. But in the plains of the Meta it is only retained on condition of the sheep being regularly shorn. If they are left to themselves, the wool becomes of a felty nature, is detached in flakes, and is replaced by a short, stiff, and shining hair. Under the influence of this burning climate, the same individual becomes in turn a woolly and a hairy animal. Now, innateness, as Prosper Lucas conceives it, cannot be appealed to in the case of changes undergone by a full-grown animal, whilst the action of conditions of life is here incontestable.

VI. We have just pointed out how heredity and conditions of life can give rise to a variety. Now, the individual which has commenced to deviate from its original type becomes in its turn a parent; it tends to transmit to its offspring the exceptional characters which distinguish it. The same facts are repeated in its offspring; and, at each generation, the actions of the conditions of life are added to each other. Thus every time heredity transmits the sum of these actions to the following generation. The faintest modification increased from father to son sometimes leads to most marked changes. Our European oxen, in the hot plains of Mariquita and Neyba gradually lost their hair, at first became pelones, and would soon have formed an entirely naked race, if the calongos had not been regularly killed. Again, pigs which have become wild in the Paramos have acquired a kind of wool under the action of a continuous, but not excessive cold. The Guinea dog and the Esquimaux dog present an analogous contrast between races of the same species.

In the preceding examples, and in many others which must be omitted, the actions in question modify organisms in order to place them in harmony with the conditions of life. Now it is intelligible that when the maximum of possible effect has once been attained, they can only fix the result obtained more fully, but can never determine a change in the opposite direction. The heat, which has by degrees deprived calongo cattle of their hair, will never restore it again; and the cold which has made our pigs woolly, will never deprive them of wool. Here, then, we find conditions of life acting as an agent of preservation and stability.

VII. In the preceding passage allusion has been made to natural forces left to themselves. It is to them that the formation is due of the wild races of all the species whose geographical area is very extended, such as the fox, jackal, lion, etc.

These races are sometimes so different that they were regarded as distinct species, as long as the intervening geographical and zoological terms were unknown. Frederick Cuvier himself made this mistake in the case of the jackals of India and those of the Senegal. Wild races have, however, never been so numerous or so distinct from each other as domesticated races.

Are we to infer from this that man exercises around himself and of himself a kind of magnetic action, as some authors seem to admit? Certainly not. In reality, he only acts upon an animal by setting in action, sometimes intentionally, sometimes unintentionally, the two agents which, hitherto, we have met with everywhere, conditions of life and heredity. By the single fact of domestication, by the confinement which is almost always the result of it, he changes entirely the natural conditions of existence. By leading in his train the animals which he has enslaved, he diversifies still more the influences which act upon them. Prompt to seize every means of rendering them most useful, he profits by the smallest modifications which show the least advantage, pushes them to their utmost limits and produces the extreme races, of which our exhibitions of animal races give such curious examples.

The chief means which man uses for the attainment of these results, which at times seem to border on the marvellous, is selection. Ever since he has possessed domestic animals he has marked out among them individuals which are better adapted than the rest to his intentions. By some kind of instinct, or unconsciously, as Darwin says, he has chosen them to breed from. By rejecting the types which he considers inferior, and only employing the higher types wherewith to propagate the species, he has directed the action of heredity in a definite direction, and has readily created races. Now, man has acted in this manner since the times spoken of in Genesis and by Chou-King, that is, for thousands of years. Is it then surprising that he should have multiplied around him hereditary forms which are more or less distinct from the primitive types?

Progressive selection would doubtless lead to numerous and varied results. Would it allow of the creation of races whose characters almost reach hemitery? The answer to this question is at least doubtful. But we have not to ask it. When by one of the actions of the conditions of life, whose origin remains obscure, an almost teratological animal form is produced, it soon disappears by the mixture of blood from different sources, if unions are left to chance. This is the reason why analogous facts are not observed in feral races. But if this form appears in a domestic animal, if it answers to any want or caprice, selection intervenes, preserves it, and multiplies it. This explains the origin of the Ancon sheep, which were all descended from a single ram of which we have spoken above; also the means by which M. Graux de Mauchamp has raised his race of sheep with silky fleeces from a single ram. These two examples show how all those peculiar races have been obtained, which in some of their characters seem to clash with the very type from which they were derived. In the canine species the beagle corresponds to the Ancon sheep; the niata cattle, which have appeared in South America since its conquest, correspond to the bull-dog, etc.

VIII. Races, when once formed under man’s influence, are fixed by the same causes which produced them. Their characters, which at first were entirely artificial, become more and more fixed, so much so, that even a very considerable change in the conditions of existence, never effaces them entirely. The acquired nature is, so to speak, welded to the original nature of the being.

This is a fact not generally recognised by naturalists and anthropologists who have touched upon these questions. For instance, it has been admitted as proved that domestic races, when they have returned to the feral state, reassume all the original characters of the species. This is a mistake. The fact is, that both with animals and plants, escaped races lose a certain number of characters, and frequently the most apparent ones, which they owe to domestication; they reassume others which they had lost during their period of servitude, but the former are more frequently only diminished and masked by the latter. If fruit-trees escaped from our orchards, if our horses, dogs, cattle, and pigs, when they have become wild, had really reassumed the original type of the species, they ought to present in every area which they inhabit the marked uniformity characteristic of animals who were never subject to man. This is not the case. They ought in particular to preserve no trace of their acquired characters. Now, the latter are partly persistent. Vans Mons has found apple-trees and pear-trees of Belgium, in a wild state, in the forest of the Ardennes. The prickles had reappeared, the fruit had become small and bitter again, but the principal cultivated varieties were still to be recognised. I have established an analogous fact with regard to cling-stone and free-stone peach-trees in a valley of the Cévennes. Similarly Martin de Moussy has recognised in the troops of dogs which have become wild in America, all the chief races from which they had been derived, although they reassumed the general characters of the tan-coloured type.