But he had more to say on the other side, that of the mutability of species, and it is these tentative views that his commentators have assumed to have been his real sentiments or belief, and for this reason place Buffon among the evolutionists, though he had little or no idea of evolution in the enlarged and thoroughgoing sense of Lamarck.
He states, however, that the presence of callosities on the legs of the camel and llama “are the unmistakable results of rubbing or friction; so also with the callosities of baboons and the pouched monkeys, and the double soles of man’s feet.”[133] In this point he anticipates Erasmus Darwin and Lamarck. As we shall see, however, his notions were much less firmly grounded than those of Erasmus Darwin, who was a close observer as well as a profound thinker.
In his chapter on the Dégénération des Animaux, or, as it is translated, “modification of animals,” Buffon insists that the three causes are climate, food, and domestication. The examples he gives are the sheep, which having originated, as he thought, from the mufflon, shows marked changes. The ox varies under the influence of food; reared where the pasturage is rich it is twice the size of those living in a dry country. The races of the torrid zones bear a hump on their shoulders; “the zebu, the buffalo, is, in short, only a variety, only a race of our domestic ox.” He attributed the camel’s hump to domesticity. He refers the changes of color in the northern hare to the simple change of seasons.
He is most explicit in referring to the agency of climate, and also to time and to the uniformity of nature’s processes in causing variation. Writing in 1756 he says:
“If we consider each species in the different climates which it inhabits we shall find perceptible varieties as regards size and form; they all derive an impress to a greater or less extent from the climate in which they live. These changes are only made slowly and imperceptibly. Nature’s great workman is time. He marches ever with an even pace and does nothing by leaps and bounds, but by degrees, gradations, and succession he does all things; and the changes which he works—at first imperceptible—become little by little perceptible, and show themselves eventually in results about which there can be no mistake. Nevertheless, animals in a free, wild state are perhaps less subject than any other living beings, man not excepted, to alterations, changes, and variations of all kinds. Being free to choose their own food and climate, they vary less than domestic animals vary.”[134]
The Buffonian factor of the direct influence of climate is not in general of so thoroughgoing a character as usually supposed by the commentators of Buffon. He generally applies it to the superficial changes, such as the increase or decrease in the amount of hair, or similar modifications not usually regarded as specific characters. The modifications due to the direct influence of climate may be effected, he says, within even a few generations.
Under the head of geographical distribution (in tome ix., 1761), in which subject Buffon made his most original contribution to exact biology, he claims to have been the first “even to have suspected” that not a single tropical species is common to both eastern and western continents, but that the animals common to both continents are those adapted to a temperate or cold climate. He even anticipates the subject of migration in past geological times by supposing that those forms travelled from the Old World either over some land still unknown, or “more probably” over territory which has long since been submerged.[135]
The mammoth “was certainly the greatest and strongest of all quadrupeds, but it has disappeared; and if so, how many smaller, feebler, and less remarkable species must have perished without leaving us any traces or even hints of their having existed? How many other species have changed their nature, that is to say, become perfected or degraded, through great changes in the distribution of land and ocean; through the cultivation or neglect of the country which they inhabit; through the long-continued effects of climatic changes, so that they are no longer the same animals that they once were. Yet of all living beings after man the quadrupeds are the ones whose nature is most fixed and form most constant; birds and fishes vary much more easily; insects still more again than these; and if we descend to plants, which certainly cannot be excluded from animated nature, we shall be surprised at the readiness with which species are seen to vary, and at the ease with which they change their forms and adopt new natures.”[136]
The following passages, debarring the error of deriving all the American from the Old World forms, and the mistake in supposing that the American forms grew smaller than their ancestors in the Old World, certainly smack of the principle of isolation and segregation, and this is Buffon’s most important contribution to the theory of descent.
“It is probable, then, that all the animals of the New World are derived from congeners in the Old, without any deviation from the ordinary course of nature. We may believe that, having become separated in the lapse of ages by vast oceans and countries which they could not traverse, they have gradually been affected by, and derived impressions from, a climate which has itself been modified so as to become a new one through the operations of those same causes which dissociated the individuals of the Old and the New World from one another; thus in the course of time they have grown smaller and changed their characters. This, however, should not prevent our classifying them as different species now, for the difference is no less real though it dates from the creation. Nature, I maintain, is in a state of continual flux and movement. It is enough for man if he can grasp her as she is in his own time, and throw but a glance or two upon the past and future, so as to try and perceive what she may have been in former times and what one day she may attain to.”[137]