Sex and Society: Studies in the Social Psychology of Sex. William Isaac Thomas
scruple that the production of females from fertilized ova increases with the temperature and food supply, and decreases as these diminish.12
Nor are there many facts more significant than the simple and well-known one that within the first eight days of larval life the addition of food will determine the striking and functional differences between worker and queen.13
It is certainly no mere chance, but agrees with other well-known facts, that for the generation of the female organ more favorable external circumstances must prevail, while the male organ may develop under very much more unfavorable conditions.14
These facts are not conclusive, but they all point in the same direction, and are probably sufficient to establish a connection between food conditions and the determination of sex. But behind the mere fact that a different attitude toward food determines difference of sex lies the more fundamental—indeed, the real—explanation of the fact, and this chemists and physiologists are not at present able to give us. Researches must be carried farther on the effect of temperature, light, and water on variation, before we may hope to reach a positive conclusion. We can only assume that the chemical constitution of the organism at a given moment conditions the sex of the offspring, and is itself conditioned by various factors—light, heat, water, electricity, etc.—and that food is one of these variables.15 It is sufficient for our present purpose that sex is a constitutional matter, indirectly dependent upon food conditions; that the female is the result of a surplus of nutrition; and that the relation reported among the lower forms persists in the human species.
In close connection with the foregoing we have the fact, reported by Maupas,16 that certain Infusorians are capable of reproducing asexually for a number of generations, but that, unless the individuals are sexually fertilized by crossing with unrelated forms of the same species, they finally exhibit all the signs of senile degeneration, ending in death.17 After sexual conjugation there was an access of vitality, and the asexual reproduction proceeded as before. "The evident result of these long and fatiguing experiments is that among the ciliates the life of the species is decomposed into evolutional cycles, each one having for its point of departure an individual regenerated and rejuvenated by sexual copulation."18
The results obtained by Maupas receive striking confirmation in the universal experience of stock-breeders, that, in order to keep a breed in health, it is necessary to cross it occasionally with a distinct but allied variety. It appears, then, that a mixture of blood has a favorable effect on the metabolism of the organism, comparable to that of abundant nutrition, and that innutrition and in-and-in breeding are alike prejudicial.
If this is true, and if heightened nutrition yields an increased proportion of females, we ought to find that breeding-out is favorable to the production of females, and breeding-in to the production of males; and a considerable body of evidence in favor of this assumption exists.19
Observations of above 4,000 cases show that, among horses, the more the parent animals differ in color, the more the female foals outnumber the male. Similarly, in-and-in-bred cattle give an excessively large number of bull calves. Liaisons produce an abnormally large proportion of females;20 incestuous unions, of males.21 Among the Jews, who frequently marry cousins, the percentage of male births is very high.
According to Mr. Jacobs' comprehensive manuscript collection of Jewish statistics … the average proportion of male and female Jewish births registered in various countries is 114.5 males to 100 females, whilst the average proportion among the non-Jewish population of the corresponding countries is 105.25 males to 100 females. … His collection includes details of 118 mixed marriages; of these 28 are sterile, and in the remainder there are 145 female children and 122 male—that is, 118.82 females to 100 males.22
The testimony is also tolerably full that among metis and among exogamous peoples the female birth-rate is often excessively high.23
Viewed with reference to activity, the animal is an advance on the plant, from which it departs by morphological and physiological variations suited to a more energized form of life; and the female may be regarded as the animal norm from which the male departs by further morphological variations. It is now well known that variations are more frequent and marked in males than in females. Among the lower forms, in which activity is more directly determined mechanically by the stimuli of heat, light, and chemical attraction, and where in general the food and light are evenly distributed through the medium in which life exists, and where the limits of variation are consequently small, the constitutional nutritive tendency of the female manifests itself in size. Among many Cephalopoda and Cirripedia, and among certain of the Articulata, the female is larger than the male. Female spiders, bees, wasps, hornets, and butterflies are larger than the males, and the difference is noticeable even in the larval stage. So considerable is the difference in size between the male and female cocoons of the silk-moth that in France they are separated by a particular mode of weighing.24 The same superiority of the female is found among fishes and reptiles; and this relation, wherever it occurs, may be associated with a habit of life in which food conditions are simple and stimuli mandatory. As we rise in the scale toward backboned and warm-blooded animals, the males become larger in size; and this reversal of relation, like the development of offensive and defensive weapons, is due to the superior variational tendency of the male, resulting in characters which persist in the species wherever they prove of life-saving advantage.25
The superior activity and variability of the male among lower forms has been pointed out in great detail by Darwin and confirmed by others.
Throughout the animal kingdom, when the sexes differ in external appearance, it is, with rare exceptions, the male which has been more modified; for, generally, the female retains a closer resemblance to the young of her own species, and to other adult members of the same group. The cause of this seems to lie in the males of almost all animals having stronger passions than the females.26
Darwin explains the greater variability of the males—as shown in more brilliant colors, ornamental feathers, scent-pouches, the power of music, spurs, larger canines and claws, horns, antlers, tusks, dewlaps, manes, crests, beards, etc.—as due to the operation of sexual selection, meaning by this "the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction,"27 the female choosing to pair with the more attractive male, or the stronger male prevailing in a contest for the female. Wallace28 advanced the opposite view, that the female owes her soberness to the fact that only inconspicuous females have in the struggle for existence escaped destruction during the breeding season. There are fatal objections to both these theories; and, taking his cue from Tylor,29 Wallace himself, in a later work, suggested what is probably the true explanation, namely, that the superior variability of the male is constitutional, and due to general laws of growth and development. "If ornament," he says, "is the natural product and direct outcome of superabundant health and vigor, then no other mode of selection is needed to account for the presence of such ornament."30 That a tendency to spend energy more rapidly should result in more striking morphological variation is to be expected; or, put otherwise, the fact of a greater variational tendency in the male is the outcome of a constitutional inclination to destructive metabolism. It is a general law in the courtship of the sexes that the male seeks the female. The secondary sexual characters of the male are developed with puberty, and in some cases these sexual distinctions come and go with the breeding season. What we know as physiological energy is the result of the dissociation of atoms in the organism; expressions of energy are the accompaniment of the katabolic or breaking-up process, and the brighter color of the male, especially at the breeding season, results from the fact that the waste products of the katabolism are deposited as pigments.
When we compare the sexes of mankind morphologically, we find a greater tendency to variation in man:31
All the secondary sexual characters of man are highly variable, even within the limits of the same race; and they differ much in the several races. … Numerous measurements carefully made of the stature, the circumference of the neck and chest, the length of the backbone and of