As a rule, among the Mammals at any rate, brilliant coloration and weapons of offence are not associated in the same animal. The Baboons, and the Mandrill in particular, are exceptions, for these animals are provided with most formidable “tusks,” the canines of both upper and lower jaws being of great size, and opposed one to another in such a way that they wear away to form sharp, angular cutting-edges, more murderous than the fangs of the Tiger.
Reference has been made already to the existence of large sound resonators for the purpose of increasing the volume of the voice in the Orang, Gorilla and Chimpanzee. Some of the Gibbons are also well provided in this direction. But the most striking instances of the kind are furnished by the Orang, and the monkeys known as Howlers. In these last the base of the hyoid, as the skeleton for the support of the tongue is called, is fashioned into a deep bony cup, which has the effect of intensifying the volume of the voice to a most surprising extent. But more than this, apparently for the protection of this bony voice-bowl the upright branches of the lower jaw have become remarkably deepened, and widened, a correlation of growth between unrelated parts which is fraught with deep significance. “Terrific,” “terrible” and “harrowing” are terms which have been used by travellers like Bates, Belt and Wallace in describing the cavernous roar of these animals, a roar which will easily carry two miles. It would seem that these vocal efforts are not merely confined to what we may call the “Courting” season, as is the roar of the stag, but that they are heard nightly at dusk. They may be resumed again at dawn, and re-awakened when thunder-clouds gather. They have become the normal method of giving vent to excitement, and probably are intensified when isolated males are desirous of discovering the whereabouts of females equally anxious to find a mate.
Among the Apes we meet, as with the human species, with both monogamy and polygamy. But it would be dangerous to assume that the reasons for polygamy are the same in both. Polygamy, indeed, has by no means always the same significance. In the most primitive, half-human races of the past, as with the man-like Apes to-day, polygamy is determined by accident rather than choice. These extinct peoples, like the great anthropoids, were normally monogamous, but on the death of a male in conflict with his neighbour, or from other causes, his mate would probably of her own free will seek out the nearest male and even if he were already mated would be at once adopted into the family circle. This certainly happens in the case of the Gorilla and Chimpanzee to-day. But among living races of mankind, both savage and civilized, multiplicity of wives is a matter of choice on the part of the male, and in many cases to achieve this females from other tribes have to be secured—either by purchase or conquest. With the lower apes, or “monkeys,” polygamy only obtains among gregarious species; and either because the birth-rate of the females exceeds that of the males, or because a considerable number of young males are killed annually by exciting the jealousy of the older males, who are exceedingly pugnacious.
CHAPTER IV
AT DAGGERS DRAWN
The Birth of Weapons—All Flesh is Grass—Utility and Ornament—The Fever of Love—The “Challenge” of the Deer—What it means—More about “Hormones”—“Hummel” Stags—The Age of Deer—The “Courtship” of the Moose—Types of Antlers—Antlered Females—Fighting Topi—The Lance of the Oryx in the Lion’s Flanks—Happiness and Hartebeestes—Odoriferous Suitors—The Bloody Sweat of the Hippopotamus—The Elephant in Love—Concerning Tusks—Polygamy.
From Apes to Antelopes is a far cry, but contrasts are always helpful. Antelopes and Deer, Zebras and Elephants, Rhinoceroses and Swine, are types, taken at random, of that great and important group of animals known as the “Ungulates,” or “Hoofed” animals. These illustrate in a very striking manner what is meant by the term “Secondary Sexual Characters.” They demonstrate no less forcibly what is meant by the term “Sexual Selection.” They are valuable in this connection, because of the often formidable weapons, in the shape of horns and tusks, which so many species have developed during the struggle for mates.
But “Sexual Selection” will not explain their origin, and it is difficult, in the present state of our knowledge, to discover any clues which will reveal this. In seeking these there are certain broad aspects of the problem which are not to be lost sight of. In the first place, horns, at any rate, are confined to the hoofed animals. That the various types of hoofed animals, living and extinct, have had a common ancestry, no one at the present day will probably call in question. The relationship, however, of the various living types, one to another, is by no means always apparent: the missing links are to be sought in the records of the rocks.
When the whole of the evidence comes to be surveyed, and not till then, it becomes apparent that this wonderful diversity is the result of complex factors. That the conditions of existence have controlled the results is beyond question; but it is equally certain that these conditions have been merely controlling and not causative. In other words, we must regard each of these different groups or types—Deer, Antelopes, Horses, Elephants, Swine, and so on—as witnesses of what we call “Heredity.” They are so many “Diathetic types.” That is to say, the forms, or individuals, belonging to each type have inherited certain peculiarities in common; they display a “Diathesis” as the doctors call it: an inherent, inborn tendency, or habit of growth, in a definite direction: a tendency which, ever and anon, develops new qualities, takes new directions. And thus it is that we get Oxen—using this term in its widest sense and not in its special sense—Antelopes, Goats and Sheep, for example. These have, among other things, a “diathesis” in the direction of horn production, and each, too, of a different type. What is meant by this apparently mystifying term “diathesis” will perhaps be made clear by taking the case of the Ox and the Sheep. While very different in appearance, these live on precisely similar food; yet no one has any difficulty in discriminating between the taste of beef and mutton. In the marvellous chemical laboratory of the body the grass gathered in the same field is converted into flesh which even in its uncooked state is easily distinguishable. Though for the purposes of this illustration domesticated animals have been used, the same is true of their wild relations. Sportsmen tell us that the various types of Antelopes and the Zebra, which may be seen feeding together, have yet flesh of very different qualities. These qualities are to be attributed neither to “Natural” nor to “Sexual” selection; they are “accidents.” Similarly, their horns are the witness of a horn-producing “diathesis”: the various divergencies in curvature, and in the form of their spirals, or the number of their encircling rings—as in the horns of Antelopes—are to be interpreted in like fashion. These twists and turns vary in the same way that the taste of the flesh varies, and for the same reason; that is to say, they are not the outcome of “Sexual Selection,” nor have they been brought about by “Natural Selection” to serve the purpose of “Recognition marks,” as Wallace would have us believe.