Imágenes de páginas
PDF
EPUB

136

EVIDENCE OF GEOLOGY. examined, and that the remains they contain of extinct animals represent the fauna of a small territory only, and that these have been preserved only under very rare conditions; so that, as Sir Charles Lyell has well expressed it, we have “a history of the world imperfectly kept and written in a changing dialect ; of this history we possess the last volume alone, relating only to two or three countries ; of this volume, only here and there a short chapter has been preserved; and of each page, only here and there a few lines.”

Imperfect as we have seen geological record to be, all its direct evidence is in favour of evolution. All the earlier types of living things present a less degree of specialization than the later ones.

Thus the Palæozoic Crustacea, the Trilobites, are most nearly allied to the Edriophthalmia, and are comparatively little specialized; the Mesozoic era presents us with macrurous forms ; and the Tertiary strata contain Brachyura *. The most ancient corals are of a far simpler type than those of more recent strata. Every one admits that the existing Cephalopoda are more highly developed than the ancient Tetrabranchiate Ammonites and Nautili; and the most ancient mammalian remains are much less specialized than those of the tertiary formations. Examples of this kind might be

* L. Agassiz on Classification.

OLDER FORMS INTERMEDIATE.

137

greatly multiplied; whilst, on the other hand, no cases can be cited in which the more ancient forms have degenerated, although many highly specialized types have become extinct.

A vast number of extinct forms are intermediate between existing types. The chain connecting the horse with the less specialized palæotherial type has been already mentioned. The Palæotheria and Hipparion were clearly intermediate between the highly specialized horse and tapir of to-day (see Plates VI. & VII.). The Halitherium is a link, according to Prof. Flower, between the Sirenia and hoofed animals, whilst Zeuglodon and Squalodon are believed by Huxley to connect cetaceans with the aquatic carnivora. Barrande asserts (and a higher authority could not be given) of the Invertebrata that he is every day taught that, although Palæozoic animals can certainly be classed under existing groups, yet at that ancient period the groups were not so distinctly separated as they are now*.

The fossils of other continents than the Old World bear the same relation to their existing faunas that those of Europe do to its present inhabitants. The fossil marsupials of Australia and the Macrauchenia and Edentates of America are undoubtedly related to their present faunas.

* Darwin, “Origin of Species,' p. 302.

138

IMPERFECTION OF GEOLOGY.

Thus we see that the relations of existing and extinct animals are definite, and favourable to the view of evolution ; whilst the extremely imperfect nature of geological record explains the paucity of the evidence it affords.

EMBRYOLOGY.

139

CHAPTER XVI.

THE EVOLUTION OF MAN.

As far as the physical nature of man is concerned, this subject has been so ably treated by Huxley in his · Man's Place in Nature,' by Darwin in his * Descent of Man,' and by Häckel in his' General Morphology,' that nothing more than a slight résumé will be attempted here.

Embryology teaches us that the process of development is the same in man as in all the other higher vertebrates; it is only in the later stages of the life of the embryo that it comes to differ from that of any other mammal; for a long time it remains identical with that of the higher monkeys; even in the middle of gestation the arms are longer than either the spine or legs, as in the anthropomorphous apes *; and the curvature of the spine, so characteristic of man, is not acquired until long after birth.

All the most distinguished naturalists of the present day admit that man is so nearly related to the higher apes that the Linnæan order Primates

* Huxley, · Vertebrated Animals,' p. 493.

140

DIFFERENT FORMS OF MAN.

lana

has been revived in the place of Cuvier's Bimana and Quadrumana.

The different genera and families of the Primates differ more in anatomical characters from each other and from the highest apes than these differ from man*. It is true a great break exists in the organic chain between the highest apes and man; but, as Prof. Schaaffhausen has remarked, “ at some future period, not very distant as measured by centuries, the civilized nations of man will almost certainly exterminate and replace throughout the world the savage races. At the same time, the anthropomorphous apes will no doubt be exterminated. The break will then be rendered wider ; for it will intervene between man in a more civilized state than the Caucasian, as we may hope, and some ape as low as the baboon, instead of, as at present, between the negro or Australian and the gorilla ”t.

The difference of conformation, especially of the skull, in the different races of man is really immense. The narrow skull of the African type,

with its projecting jaws, is in marked contrast · with the broad-headed European skull, characterized by a prominent forehead and retreating jaws; whilst the beetle-browed flattened calvarium of the

* Huxley, Man's Place in Nature.'
† Darwin's · Descent of Man,' vol. i. p. 201.

vo

« AnteriorContinuar »