Monkeys and anthropoid apes—Erect attitude—Curvature of the spine—Brain—Skull—Teeth—Other characters—Differences less accentuated in the fœtus and the young than in the adult.
DISTINCTIVE MORPHOLOGICAL CHARACTERS OF HUMAN RACES.
Stature: Individual limits—Dwarfs and giants—Average stature of different populations—Influence of environment—Differences according to sex—Reconstitution from the long bones—Teguments: Skin—Hair of head and body—Four principal types—Microscopic structure—Correlation between the hair of the head and the pilosity of the body—Pigmentation: Colouring of the skin, the eyes, and the hair—Changes in the pigment.
Distinctive Characters of Man and Apes.
THE physical peculiarities distinguishing man from the animals most nearly allied to him in organisation, and those which differentiate human races one from another, are almost never the same. I shall in a few words point out the former, dwelling at greater length on the latter, which have a more direct connection with our subject.
From the purely zoological point of view man is a placental or Eutherian mammal, because he has breasts, because he is more or less covered with hair, because his young, nourished in the womb of the mother through the medium of the placenta, come fully formed into the world, without needing to be protected in a pouch or fold of skin, as in the case of the marsupial mammals (implacentals or Metatherians), or completing their development in a hatched egg, as in the case of the monotremata or Prototherians.
In this sub-class of the placental mammals, man belongs to the order of the Primates of Linnæus, in view of certain peculiarities of his physical structure—the pectoral position of the breasts, the form, number, and arrangement of the teeth in the jaw, etc.
The order of the Primates comprises five groups or families: the Marmosets (Hapalidæ), the Cebidæ, the Cercopithecidæ, the anthropoid apes (Simidæ), and lastly, the Hominidæ.[9] Putting aside the first two groups of Primates, which inhabit the New World, and which are distinguished from the three other groups by several characters, let us concern ourselves with the apes of the Old World and the Hominians. Let us at the outset remember that the monkeys and the anthropoid apes exhibit the same arrangement of teeth, or, as it is termed, the same “dental formula,” as man. This formula, a character of the first importance in the classification of mammals, is summed up, as we know, in the following manner: four incisors, two canines, four premolars, and six molars in each jaw.
The Cercopithecidæ walk on their four paws, and this four-footed attitude is in harmony with the structure of their spine, in which the three curves, cervical, dorsal, and lumbar, so characteristic in man, are hardly indicated; thus the spine seems to form a single arch from the head to the tail. As to this last appendage, it is never wanting in these monkeys, which are also provided with buttock or ischiatic callosities, and often with cheek-pouches.
The anthropoid apes form a zoological group of four genera only. Two of these genera, the gorilla and the chimpanzee, inhabit tropical Africa; the two others, the orang-utan and the gibbon, are confined to the south-east of Asia, or, to be more precise, to Indo-China, and the islands of Sumatra and Borneo. We can even reduce the group in question to three genera only, for many naturalists consider the gibbon as an intermediate form between the anthropoid apes and the monkeys.[10] The anthropoids have a certain number of characters in common which distinguish them from the monkeys. Spending most of their life in trees, they do not walk in the same way as the macaques or the baboons. Always bent (except the gibbon), they move about with difficulty on the ground, supporting themselves not on the palm of the hand, as do the monkeys, but on the back of the bent phalanges. They have no tail like the other apes, nor have they cheek-pouches to serve as provision bags. Finally, they are without those callosities on the posterior part of the body which are met with in a large number of Cercopithecidæ, attaining often enormous proportions, as for instance, among the Cynocephali. The gibbon alone has the rudiments of ischiatic callosities.