The Sexes in Science and History - Eliza Burt Gamble

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be rather a state antecedent to sex than a union of sexes in one organism. Among all the higher orders of life, whether animal or vegetable, the sex elements, female and male, are recognized as the two great factors in creation.

      As, among all the animals in which there has been a separation of sexes, there has been established a division of labour, the consequent specialization of organs and the differentiation of parts form the true line of demarcation in the march of the two diverging columns. Doubtless in the future, when our knowledge of the history of life on the earth has become more extended, it will be found that it is only by tracing the processes of differentiation throughout the two entire lines of development that we may hope to unravel all the mysteries bound up in the problem of sex, or to understand the fundamental differences in character and constitution caused by this early division of labour.

       THE ORIGIN OF SEX DIFFERENCES

       Table of Contents

      We have observed that, according to naturalists, the earliest forms of life which appeared on the earth were androgynous or hermaphrodite, that the two elements necessary for reproduction were originally confined within one and the same individual within which were carried on all the functions of reproduction. Later, however, a division of labour arose, and these two original functions became detached, after which time the reproductive processes were carried on only through the commingling of elements prepared by, or developed within, two separate and distinct individuals.

      As the belief is entertained by our guides in this matter that greater differentiation, or specialization of parts, denotes higher organization, it is believed that the division of labour by which the germ is prepared by one individual and the sperm by another individual, as is the case at the present time with all the higher orders of life, constitutes an important step in the line of progress. Here this line of argument ceases, and, until very recent times, concerning the course of development followed by each sex little has been heard. This silence on a subject of such vital importance to the student of biology is not perhaps difficult to understand; the conclusion, however, is unavoidable that the individual which must nourish and protect the germ, and by processes carried on within her own body provide nourishment for the young during its prenatal existence, and sometimes for years after birth, must have the more highly specialized organism, and must, therefore, represent the higher stage of development. Indeed, it is admitted by scientists that the advance from the egg-layers to the milk-givers indicates one of the most important steps in the entire line of development; and yet the peculiar specialization of structure necessary for its accomplishment was for the most part carried on within the female organism.

      Concerning the origin of sex in the individual organism little seems to be known; as a result, however, of observations on the development of the reproductive organs in the higher vertebrates, and especially in birds, it is believed that there exists a “strict parallelism between the individual and the racial history,”—that the three main stages in the development of the chick, viz.: (1) germi-parity, (2) hermaphroditism, and (3) differentiated unisexuality, correspond to the three great steps of historic evolution.

      By a careful investigation of the facts connected with the development of unisexual forms, we are enabled to discover the early beginnings of the characteristics which distinguish the two sexes throughout their entire course. We are told that with animals which have their sexes separate, in addition to strictly sexual difference

      the male possesses certain organs of sense or locomotion, of which the female is quite destitute, or has them more highly developed, in order that he may readily find or reach her; or again the male has special organs of prehension for holding her securely. These latter organs, of infinitely diversified kinds, graduate into those which are commonly ranked as primary.4

      The female, on the other hand, in addition to those sexual characters which are strictly primary, has “organs for the nourishment or protection of her young, such as the mammary glands of mammals, and the abdominal sacks of the marsupials.” In addition to these she is frequently provided with organs for the defence of the community; for instance, “the females of most bees are provided with a special apparatus for collecting and carrying pollen, and their ovipositor is modified into a sting for the defence of the larvæ and the community.” We are assured by Mr. Darwin that many similar cases could be given.5

      Here, then, with almost the first or primary step toward sexual differentiation, may be observed the establishment of that peculiar bias which upon investigation will be seen to extend all along the two lines of sexual demarcation, and which (to anticipate the conclusions of our argument), as soon as mankind is reached, appears in the male as extreme egoism or selfishness, and in the female as altruism or care for other individuals outside of self.

      We are assured, however, that it is not alone to the reproductive organs and their functions that we are to look for the chief differences in the constitution and character of the sexes. Neither is it entirely to Natural Selection that we are to seek for the causes which underlie the specialization peculiar to the two diverging lines of sexual demarcation; in addition to primary sexual divergences, there are also “secondary sexual characters” which are of great importance to their possessor. Indeed, from the prominence given to Sexual Selection by Mr. Darwin, it would seem that it played a part in the development of males quite equal to that of Natural Selection itself.

      Now the difference between Natural Selection and Sexual Selection is that, whereas, in the former, characters are developed and preserved which are of use to the individual in overcoming the unfavourable conditions of environment, by the latter, only those characters are acquired and preserved which assist the individual in overcoming the obstacles to reproduction; or, to use Mr. Darwin’s own language:

      

      [Sexual Selection] depends on the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction. … [Where] the males have acquired their present structure, not from being better fitted to survive in the struggle of existence, but from having gained an advantage over other males, and from having transmitted this advantage to their male offspring alone, sexual selection must here have come into action. … A slight degree of variability leading to some advantage, however slight, in reiterated deadly contests would suffice for the work of sexual selection; and it is certain that secondary sexual characters are eminently variable. Just as man can give beauty, according to his standard of taste, to his male poultry, or more strictly can modify the beauty originally acquired by the parent species, can give to the Sebright bantam a new and elegant plumage, an erect and peculiar carriage—so it appears the female birds in a state of nature, have by a long selection of the more attractive males, added to their beauty or other attractive qualities.6

      Thus, according to Mr. Darwin, it is through a long selection by females of the more attractive males that the present structure of the latter has been acquired. If, in a short time, a man can give elegant carriage and beauty to his bantams, according to his standard of beauty, he can see no reason to doubt that female birds, by selecting during thousands of generations the most melodious or beautiful males, according to their standard of beauty, might produce a marked effect. He says:

      To sum up on the means through which, as far as we can judge, sexual selection has led to the development of secondary sexual characters. It has been shown that the largest number of vigorous offspring will be reared from the pairing of the strongest and best armed males, victorious in contests over other males, with the most vigorous and best-nourished females, which are the first to breed in the spring. If such females select the more attractive, and at the same time vigorous males, they will rear a larger number of offspring than the retarded females, which must pair with the less vigorous and less attractive males. … The advantage thus gained by the more vigorous pairs in rearing a larger number of offspring has apparently sufficed to render sexual selection efficient.7

      Although the belief is common among naturalists that the appearance of secondary sexual characters belonging to males is greatly influenced by female choice, a majority of writers upon this subject are not in sympathy with Mr. Darwin’s theory concerning the origin

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