Westermarck, in a chapter of his History of Human Marriage, dealing with the question of "A Human Pairing Season in Primitive Times," brings forward evidence showing that spring, or, rather, early summer, is the time for increase of the sexual instinct, and argues that this is a survival of an ancient pairing season; spring, he points out, is a season of want, rather than abundance, for a frugivorous species, but when men took to herbs, roots, and animal food, spring became a time of abundance, and suitable for the birth of children. He thus considers that in man, as in lower animals, the times of conception are governed by the times most suitable for birth.
Rosenstadt, as we shall see later, also believes that men to-day have inherited a physiological custom of procreating at a certain epoch, and he thus accounts for the seasonal changes in the birthrate.
Heape, who also believes that "at one period of its existence the human species had a special breeding season," follows Wiltshire in suggesting that "there is some reason to believe that the human female is not always in a condition to breed." (W. Heape, "Menstruation and Ovulation of Macacus rhesus," Philosophical Transactions, 1897; id. "The Sexual Season of Mammals," Quarterly Journal Microscopical Science, 1900.)
Except, however, in one important respect, with which we shall presently have to deal, few attempts have been made to demonstrate any annual organic sexual rhythm. The supposition of such annual cycle is usually little more than a deduction from the existence of the well-marked seasonal sexual rhythm in animals. Most of the higher animals breed only once or twice a year, and at such a period that the young are born when food is most plentiful. At other periods the female is incapable of breeding, and without sexual desires, while the male is either in the same condition or in a condition of latent sexuality. Under the influence of domestication, animals tend to lose the strict periodicity of the wild condition, and become apt for breeding at more frequent intervals. Thus among dogs in the wild state the bitch only experiences heat once a year, in the spring. Among domesticated dogs, there is not only the spring period of heat, early in the year, but also an autumn period, about six months later; the primitive period, however, remains the most important one, and the best litters of pups are said to be produced in the spring. The mare is in season in spring and summer; sheep take the ram in autumn.[[128]] Many of the menstruating monkeys also, whether or not sexual desire is present throughout the year, only conceive in spring and in autumn. Almost any time of the year may be an animal's pairing season, this season being apparently in part determined by the economic conditions which will prevail at birth. While it is essential that animals should be born during the season of greatest abundance, it is equally essential that pairing, which involves great expenditure of energy, should also take place at a season of maximum physical vigor.
As an example of the sexual history of an animal through the year, I may quote the following description, by Dr. A. W. Johnstone, of the habits of the American deer: "Our common American deer, in winter-time, is half-starved for lack of vegetation in the woods; the low temperature, snow, and ice, make his conditions of life harder for lack of the proper amount of food, whereby he becomes an easier prey to carnivorous animals. He has difficulty even in preserving life. In spring he sheds his winter coat, and is provided with a suit of lighter hair, and while this is going on the male grows antlers for defence. The female about this time is far along in pregnancy, and when the antlers are fully grown she drops the fawn. When the fawns are dropped vegetation is plentiful and lactation sets in. During this time the male is kept fully employed in getting food and guarding his more or less helpless family. As the season advances the vegetation increases and the fawn begins to eat grass. When the summer heat commences the little streams begin to dry up, and the animal once more has difficulty in supporting life because of the enervating heat, the effect of drought on the vegetation, and the distance which has to be traveled to get water; therefore, fully ten months in each year the deer has all he can do to live without extra exertion incident to rutting. Soon after the autumn rains commence vegetation becomes more luxurious, the antlers of the male and new suits of hair for both are fully grown, heat of the summer is gone, food and drink are plentiful everywhere, the fawns are weaned, and both sexes are in the very finest condition. Then, and then only, in the whole year, comes the rut, which, to them as to most other animals, means an unwonted amount of physical exercise besides the everyday runs for life from their natural enemies, and an unusual amount of energy is used up. If a doe dislikes the attention of a special buck, miles of racing result. If jealous males meet, furious battles take place. The strain on both sexes could not possibly be endured at any other season of the year. With approach of cold weather, climatic deprivations and winter dangers commence and rut closes. In all wild animals, rut occurs only when the climatic and other conditions favor the highest physical development. This law holds good in all wild birds, for it is then only that they can stand the strain incident to love-making. The common American crow is a very good study. In the winter he travels around the ricefields of the South, leading a tramp's existence in a country foreign to him, and to which he goes only to escape the rigors of the northern climate. For several weeks in the spring he goes about the fields, gathering up the worms and grubs. After his long flight from the South he experiences several weeks of an almost ideal existence, his food is plentiful, he becomes strong and hearty, and then he turns to thoughts of love. In the pairing season he does more work than at any other time in the year: fantastic dances, racing and chasing after the females, and savage fights with rivals. He endures more than would be possible in his ordinary physical state. Then come the care of the young and the long flights for water and food during the drought of the summer. After the molt, autumn finds him once more in flock, and with the first frosts he is off again to the South. In the wild state, rut is the capstone of perfect physical condition." (A. W. Johnstone, "The Relation of Menstruation to the other Reproductive Functions," American Journal of Obstetrics, vol. xxxii, 1895.)
Wiltshire ("Lectures on the Comparative Physiology of Menstruation," British Medical Journal, March, 1888) and Westermarck (History of Human Marriage, Chapter II) enumerate the pairing season of a number of different animals.
With regard to the breeding seasons of monkeys, little seems to be positively known. Heape made special inquiries with reference to the two species whose sexual life he investigated. He was informed that Semnopithecus entellus breeds twice a year, in April and in October. He accepts Aitcheson's statement that the Macacus rhesus, in Simla, copulates in October, and adds that in the very different climate of the plains it appears to copulate in May. He concludes that the breeding season varies greatly in dependence on climate, but believes that the breeding season is always preserved, and that it affects the sexual aptitude of the male. He could not make his monkeys copulate during February or March, but is unable to say whether or not sexual intercourse is generally admitted outside the breeding season. He quotes the observation of Breschet that monkeys copulate during pregnancy.
In primitive human races we very frequently trace precisely the same influence of the seasonal impulse as may be witnessed in the higher animals, although among human races it does not always result that the children are born at the time of the greatest plenty, and on account of the development of human skill such a result is not necessary. Thus Dr. Cook found among the Eskimo that during the long winter nights the secretions are diminished, muscular power is weak, and the passions are depressed. Soon after the sun appears a kind of rut affects the young population. They tremble with the intensity of sexual passion, and for several weeks much of the time is taken up with courtship and love. Hence, the majority of the children are born nine months later, when the four months of perpetual night are beginning. A marked seasonal periodicity of this kind is not confined to the Arctic regions. We may also find it in the tropics. In Cambodia, Mondière has found that twice a year, in April and September, men seem to experience a "veritable rut," and will sometimes even kill women who resist them.[[129]]
These two periods, spring and autumn—the season for greeting the appearance of life and the season for reveling in its final fruition—seem to be everywhere throughout the world the most usual seasons for erotic festivals. In classical Greece and Rome, in India, among the Indians of North and South America, spring is the most usual season, while in Africa the yam harvest of autumn is the season chiefly selected. There are, of course, numerous exceptions to this rule, and it is common to find both seasons observed. Taking, indeed, a broad view of festivals throughout the world, we may say that there are four seasons when they are held: the winter solstice, when the days begin to lengthen and primitive man rejoices in the lengthening and seeks to assist it;[[130]] the vernal equinox, the period of germination and the return of life; the summer solstice, when the sun reaches its height; and autumn, the period of fruition, of thankfulness, and of repose. But it is rarely that we find a people seriously celebrating more than two of these festival seasons.