The Antiquity of Man

by Sir Charles Lyell

As one of the consequences of this law, he says that species, genera, and orders are, on the whole, best limited in plants of higher grade, the dicotyledons better than the monocotyledons, and the Dichlamydeae better than the Achlamydeae.

Mr. Darwin remarks, "We can, perhaps, understand the apparently quicker rate of change in terrestrial, and in more highly organised productions, compared with marine and lower productions, by the more complex relations of the higher beings to their organic and inorganic conditions of life."*

(* "Origin of Species" 3rd edition page 340.)

If we suppose the mammalia to be more sensitive than are the inferior classes of the vertebrata, to every fluctuation in the surrounding conditions, whether of the animate or inanimate world, it would follow that they would oftener be called upon to adapt themselves by variation to new conditions, or if unable to do so, to give place to other types. This would give rise to more frequent extinction of varieties, species, and genera, whereby the surviving types would be better limited, and the average duration of the same unaltered specific types would be lessened.

ABSENCE OF MAMMALIA IN ISLANDS CONSIDERED IN REFERENCE TO TRANSMUTATION.

But if mammalia vary upon the whole at a more rapid rate than animals lower in the scale of being, it must not be supposed that they can alter their habits and structures readily, or that they are convertible in short periods into new species. The extreme slowness with which such changes of habits and organisation take place, when new conditions arise, appears to be well exemplified by the absence even of small warm-blooded quadrupeds in islands far from continents, however well such islands may be fitted by their dimensions to support them.

Mr. Darwin has pointed to this absence of mammalia as favouring his views, observing that bats, which are the only exceptions to the rule, might have made their way to distant islands by flight, for they are often met with on the wing far out at sea. Unquestionably, the total exclusion of quadrupeds in general, which could only reach such isolated habitations by swimming, seems to imply that nature does not dispense with the ordinary laws of reproduction when she peoples the earth with new forms; for if causes purely immaterial were alone at work, we might naturally look for squirrels, rabbits, polecats, and other small vegetable feeders and beasts of prey, as often as for bats, in the spots alluded to.

On the other hand, I have found it difficult to reconcile the antiquity of certain islands, such as those of the Madeiran Archipelago, and those of still larger size in the Canaries, with the total absence of small indigenous quadrupeds, for, judging by ancient deposits of littoral shells, now raised high above the level of the sea, several of these volcanic islands (Porto Santo and the Grand Canary among others) must have existed ever since the Upper Miocene period. But, waiving all such claims to antiquity, it is at least certain that since the close of the Newer Pliocene period, Madeira, and Porto Santo have constituted two separate islands, each in sight of the other, and each inhabited by an assemblage of land shells (Helix, Pupa, Clausilia, etc.), for the most part different or proper to each island. About thirty-two fossil species have been obtained in Madeira, and forty-two in Porto Santo, only five of the whole being common to both islands. In each the living land-shells are equally distinct, and correspond, for the most part, with the species found fossil in each island respectively.

Among the fossil species, one or two appear to be entirely extinct, and a larger number have disappeared from the fauna of the Madeiran Archipelago, though still extant in Africa and Europe. Many which were amongst the most common in the Pliocene period, have now become the scarcest, and others formerly scarce, are now most numerously represented. The variety-making force has been at work with such energy—perhaps we ought to say, has had so much time for its development—that almost every isolated rock within gun-shot of the shores has its peculiar living forms, or those very marked races to which Mr. Lowe, in his excellent description of the fauna, has given the name of "sub-species."

Since the fossil shells were embedded in sand near the coast, these volcanic islands have undergone considerable alterations in size and shape by the wasting action of the waves of the Atlantic beating incessantly against the cliffs, so that the evidence of a vast lapse of time is derivable from inorganic as well as from organic phenomena.