Evolution and Adaptation

by Thomas Hunt Morgan

Finally, the case of man must be considered from the point of view of sexual selection, for Darwin claims that man has acquired a number of his secondary sexual characters in this way. For instance, the beard is an excellent case of a secondary sexual character. Darwin’s interpretation is that the beard has been retained, or even developed, through the selection by the females of those males that had this outgrowth best developed. Conversely, the absence of hair on the face of the female is supposed by Darwin to have been brought about by men selecting those women having less hair on their faces. The greater intellect, energy, courage, pugnacity, and size of man are the outcome of the competition of the males with each other, since the individual excelling in these qualities will be able to select the most desirable wife, or wives, and it is assumed will, therefore, leave more descendants. The standard of beauty has been kept up by men selecting the most beautiful women in each generation (the fate of the other married women is ignored), and this beauty is supposed to have been transmitted primarily to their daughters, but also to their sons.

Although all these forms of selection are imagined to be acting in man, either alternately or simultaneously, yet Darwin recognizes in man a number of checks to the action of sexual selection: amongst savages, the so-called communal marriages; second, infanticide, generally of the young females, which appears in some races to be practised to an astonishing degree; third, early betrothals; fourth, the holding of women as slaves.

When we recall that selection to be effective can only be carried out under very exacting conditions, we cannot but be appalled at the demands made here on our credulity. The choice of the women has produced the beard of man, the choice of man the absence of a beard in women; the competition of the males with each other is leading at the same time to the development of at least half a dozen qualities that are supposed to be male specialities, and while all this is going on the results are being checked sometimes by one means, sometimes by another. Moreover, even this is not all that we are asked to accept, for there are several other qualities of the male that are put down as secondary sexual characters. For example, let us examine what Darwin has to say in regard to the development of the voice, and of singing in man.

In man the vocal cords are about a third longer than in woman and his voice deeper. Emasculation arrests the development of the vocal apparatus, and the voice remains like that of a woman. This difference between the sexes, Darwin thinks, is due probably to long-continued use by the male “under the excitement of love, rage, and jealousy.” In other words, an appeal is again made to the Lamarckian theory, and in this case to explain the origin of an organ that conforms to all the requirements of the secondary sexual characters.

“The capacity and love for singing, or music, though not a sexual character in man,” in the sense of being confined to one sex, yet is supposed to have arisen through sexual selection in the following way: “Human song is generally admitted to be the basis or origin of instrumental music. As neither the enjoyment nor the capacity of producing musical notes are faculties of the least use to man in reference to his daily habits of life, they must be ranked amongst the most mysterious with which he is endowed.”

Man is supposed to have possessed this faculty of song from a very remote time, and even the most savage races make musical sounds, although we do not enjoy their music, or they ours.

“We see that the musical faculties, which are not wholly deficient in any race, are capable of prompt and high development, for Hottentots and Negroes have become excellent musicians, although in their native countries they rarely practise anything that we should consider music. Hence the capacity for high musical development, which the savage races of man possess, may be due either to the practice by our semi-human progenitors of some rude form of music, or simply to their having acquired the proper vocal organs for a different purpose. But in this latter case we must assume, as in the above instance of parrots, and as seems to occur with many animals, that they already possessed some sense of melody.”

Darwin sums up the evidence in the two following statements, the insufficiency of which to explain the phenomena is I think only too obvious: “All these facts in respect to music and impassioned speech become intelligible to a certain extent, if we assume that musical tones and rhythm were used by our half-human ancestors, during the season of courtship, when animals of all kinds are excited not only by love, but by the strong passions of jealousy, rivalry, and triumph. From the deeply laid principle of inherited associations, musical tones in this case would be likely to call up vaguely and indefinitely the strong emotions of a long past age.” Thus the difficulty is shifted to the shoulders of our long-lost savage ancestors; or even, in fact, to our simian forefathers, as the following paragraph indicates:—

“As the males of several quadrumanous animals have their vocal organs much more developed than in the females, and as a gibbon, one of the anthropomorphous apes, pours forth a whole octave of musical notes and may be said to sing, it appears probable that the progenitors of man, either the males or females or both sexes, before acquiring the power of expressing their mutual love in articulate language, endeavored to charm each other with musical notes and rhythm. So little is known about the use of the voice by the Quadrumana during the season of love, that we have no means of judging whether the habit of singing was first acquired by our male or female ancestors. Women are generally thought to possess sweeter voices than men, and as far as this serves as any guide, we may infer that they first acquired musical powers in order to attract the other sex. But if so, this must have occurred long ago, before our ancestors had become sufficiently human to treat and value their women merely as useful slaves. The impassioned orator, bard, or musician, when with his varied tones and cadences he excites the strongest emotions in his hearers, little suspects that he uses the same means by which his half-human ancestors long ago aroused each other’s ardent passions during their courtship and rivalry.”

We have now examined in some detail the evidence that Darwin has brought forward in support of his hypothesis of sexual selection. A running comment has been made while considering the individual cases, but it may be well to sum up the matter by briefly indicating the reasons why the hypothesis seems incompetent to explain the facts.