While the differences between the sexes have been mainly elaborated through the differences of reproductive function, yet these differences have come to be fundamental to the whole nature of the organism. In the higher animals, therefore, the sexes differ profoundly in many ways from each other. Biologists tell us that the chief difference between the male and female organism is a difference in metabolism, that is, in the rapidity of organic change which goes on within the body. In the male metabolism is much more rapid than in the female; hence the male organism is said to be more katabolic. In the female the rapidity of organic change is less; hence the female is said to be more anabolic. Put in more familiar terms, the male tends to expend energy, is more active, hence also stronger; the female tends more to store up energy, is more passive, conservative, and weaker. These fundamental differences between the sexes express themselves in many ways in the social life. The differences between man and woman, therefore, are not to be thought of as due simply to social customs and usages, the different social environment of the two sexes, but are even more due to a radical and fundamental difference in their whole nature. The belief that the two sexes would become like each other in character if given the same environment is, therefore, erroneous. That these differences are original, or inborn, and not acquired, may be readily seen by observing children of different sex. Even from their earliest years boys are more active, restless, energetic, destructive, untidy, and disobedient, while little girls are quieter, less restless, less destructive, neater, more orderly, and more obedient. These different innate qualities fit the sexes naturally for different functions in human society, and there is, therefore, a natural division of labor between them from the first. Indeed, the division of labor between the two sexes may be said to be the fundamental division of labor in human society.
The causes which produce sex in the individual are not known to any extent and are probably beyond the control of man. In each species the relative number of the two sexes is fixed by nature, probably through some obscure working of natural selection, and in practically all of the higher species of animals, man included, the number of the two sexes is relatively equal. In human society much depends upon this relative numerical equality of the two sexes. Hence it can be readily seen that it is fortunate that man does not know how to control the sex of offspring, for if he did the numerical equality of the two sexes might be disturbed and serious social results would follow.
(2) The Influence of Parental Care. Sex alone could never have produced the family in the sense of a relatively permanent group of parents and offspring. We do not begin to find the family until we get to those higher types where we find some parental care. In the lowest types the relation between the sexes is momentary and the survival of offspring is secured simply through the production of enormous numbers. Thus the sturgeon, a low type of fish, produces between one and two million of eggs at a single spawning, from which it is estimated that not more than a dozen individuals survive till maturity is reached. Thus sexual reproduction of itself necessitates no parental care and in itself could give rise in no way to the family; but quite low in the scale of life we begin to find some parental care as a device to protect immature offspring and secure their survival without the expenditure of such an enormous amount of energy in mere physiological reproduction. Even among the fishes we find some that watch over the eggs after they are spawned and care for their young by leading them to suitable feeding grounds. In such cases a much smaller number of young need to be produced in order that a few may survive until maturity is reached. In the mammals the mother, obviously, must care for the young for some time, since mammals are animals that suckle their young. But this care of the young by a single parent only foreshadows the family as we understand it. Among the mammals it is not until we reach the higher types that we find care of offspring by both parents,—a practice, however, which is common among the birds. It is evident that as soon as both parents are concerned in the care of the offspring they have a much better chance of survival. Hence, natural selection favors the growth of this type of group life and develops powerful instincts to keep male and female together till after the birth and rearing of offspring. Such we find to be the condition among many of the higher mammals, such as some of the carnivora, and especially among the monkeys and apes and man.
If it is allowable at this point to generalize from the facts given, it must be said that the family life is essentially a device of nature for the preservation of offspring through a more or less prolonged infancy. The family group and the instincts upon which it rests were undoubtedly, therefore, instituted by natural selection. Summing up, we may say, then, the animal family group owes its existence, first, to the production of child or immature forms that need more or less prolonged care; secondly, to the prolongation of this period of immaturity in the higher animals, and especially in man; thirdly, to the development, parallel with these two causes, of parental instincts which keep male and female together for the care of the offspring. It is evident, then, that the family life rests, not upon sex attraction, but upon the fact of the child and the corresponding psychological fact of parental instinct. The family, then, has been created by the very conditions of life itself and is not a man-made institution.
The Origin of the Family in the Human Species.—Two great theories of the origin of the family in the human species have in the past been more or less accepted, and these we must now examine and criticize. First, the traditional theory that the human family life was from the beginning a pure monogamy. Secondly, the so-called evolutionary theory that the human family life arose from confused if not promiscuous sex relations. The first of these theories, favored both by the Bible and Aristotle, held undisputed sway down to the middle of the nineteenth century. Then, after the publication of Darwin's Origin of Species in 1859, certain social theorists began to put forward the second theory in the name of evolution. In order that we may see precisely what the origin of the human family life was, and its primitive form, we must now proceed to criticize these two theories, especially the last, which is known as the hypothesis of a primitive state of promiscuity.
The Habits of the Higher Animals. We have already spoken of the origin of the family group in the animal world generally, but it must be admitted that there are some difficulties in arguing directly from the lower animals to man. Man is so separated from the lower animals through having passed through many higher stages of an independent evolution that in many respects his life is peculiar to itself. This is true especially of his family life. If we survey the whole range of animal life and then the whole range of human life, we find that there are but two or three striking similarities between the family life of man and that of the brutes, but a great many striking dissimilarities. The similarities may be summed up by saying that man exhibits in common with all the animals the phenomena of courtship, that is, of the male seeking to win the female, also the phenomenon of male jealousy, and we may perhaps add an instinctive aversion to crossing with the other species. These characteristics of his family life man shares with the brutes below him. There are, however, many things peculiar to the human family life that are found in no animal species below man. The most striking of these differences may be mentioned. (1) Man has no pairing season, as practically all other animals have. (2) The number of young born in the human species is on the whole much smaller than in any other animal species. (3) The dependence of offspring upon parents is far longer in the human species than in any other species. (4) Man has an antipathy to incest or close inbreeding which seems to be instinctive. This is not found clearly in any animal species below man. (5) There is a tendency among human beings to artificial adornment during the period of courtship, but not to natural ornament to any extent, as among many animal species. (6) The indorsement of society is almost invariably sought, both among uncivilized and civilized peoples, before the establishment of a new family—usually through the forms of a religious marriage ceremony. (7) Chastity in women, especially married women, is universally insisted upon, both among uncivilized and civilized peoples, as the basis of human family life. (8) There is a feeling of modesty or of shame as regards matters of sex among the human beings. (9) In humanity we find, besides animal lust, spiritual affection, or love, as a bond of union between the two sexes.
None of these peculiarities of human family life are found in the family life of any animal species below man. It might seem, therefore, that man's family life must be regarded as a special creation unconnected with the family life of the brutes below him. But this view is hardly probable, rather is impossible from the standpoint of evolution. We must say that these peculiarities of human family life are to be explained through the fact that man has passed through many more stages of evolution, particularly of intellectual evolution, than any of the animals below him. If we examine these peculiarities of man's family life carefully, we will see that they all can be explained through natural selection and man's higher intellectual development. That man has no pairing season, has fewer offspring born, and a longer period of dependence of the offspring upon parents, and the like, is directly to be explained through natural selection; while seeking the indorsement of society before forming a new family, sexual modesty, tendencies to artificial adornment, and the like, are to be explained through man's self-consciousness and higher intellectual development, also through the fuller development of his social instincts. The gap between the human family life and brute family life is, therefore, not an unbridgeable one.
That this is so, we see most clearly when we consider the family life of the anthropoid or manlike apes—man's nearest cousins in the animal world. All of these apes, of which the chief representatives are the gorilla, orangutan, and the chimpanzee, live in relatively permanent family groups, usually monogamous. These family groups are quite human in many of their characteristics, such as the care which the male parent gives to the mother and her offspring, and the seeming affection which exists between all members of the group. Such a group of parents and offspring among the higher apes is, moreover, a relatively permanent affair, children of different ages being frequently found along with their parents in such groups. So far as the evidence of animals next to man, therefore, goes, there is no reason for supposing that the human family life sprang from confused or promiscuous sex relations in which no permanent union between male and female parent existed. On the contrary, there is every reason to believe, as Westermarck says, that human family life is an inheritance from man's apelike progenitor.
The Evidence from the Lower Human Races.—The evidence afforded by the lowest peoples in point of culture even more clearly, if anything, refutes the hypothesis of a primitive state of promiscuity. The habits or customs of the lowest peoples were not well known previous to the nineteenth century. Therefore it was possible for such a theory as the patriarchal theory of the primitive family to remain generally accepted, as we have already said, down to the middle of the nineteenth century. This was the theory that the oldest or most primitive type of human family life is that depicted in the opening pages of the Book of Genesis, namely, a family life in which the father or eldest male of the family group is the absolute ruler of the group and practically owner of all persons and property. The belief that this was the primitive type of the human family life was first attacked by a German-Swiss philologist by the name of Bachofen in a work entitled Das Mutterrecht (The Matriarchate), published in 1861, in which he argued that antecedent to the patriarchal period was a matriarchal period, in which women were dominant socially and politically, and in which relationships were traced through mothers only. Bachofen got his evidence for this theory from certain ancient legends, such as that of the Amazons, and other remains in Greek and Roman literature, which seemed to point to a period antecedent to the patriarchal.
In 1876 Mr. J.F. McLennan, a Scotch lawyer, put forth, independently, practically the same theory, basing it upon certain legal survivals which he found among many peoples. With Bachofen, he argued that this matriarchal period must have been characterized by promiscuous relations of the sexes. In 1877 Mr. Lewis H. Morgan, an American ethnologist and sociologist, put forth again, independently, practically the same theory, basing it upon an extensive study of the North American Indian tribes. Morgan had lived among the Iroquois Indians for years and had mastered their system of relationship, which previously had puzzled the whites. He found that they traced relationship through mothers only, and not at all along the male line. This method of reckoning relationship, moreover, he found also characterized practically all of the North American Indian tribes, and he argued that the only explanation of it was that originally sexual relations were of such an unstable or promiscuous character that they would not permit of tracing descent through fathers.