Though Mendel knew an astonishing amount about inheritance a half-century ago, it is worth noting that the foundation upon which rests our present knowledge of sex has been discovered less than twenty years before—the reference is, of course, to the chromosomes as the carriers of inheritance. While from the standpoint of biology the opinions of two decades ago about sex literally belong to a different age, some of them have been so persistent in sociological thought and writings that they must be briefly reviewed in order that the reader may be on his guard against them. Books which still have a wide circulation deal with the sex problem in terms of a biology now no more tenable than the flatness of the earth.
On the one hand were the ancient traditions of male predominance in inheritance, reinforced by the peculiar emphasis which animal breeding places upon males. On the other hand, biologists like Andrew Wilson[[5]] had argued as early as the seventies of the past century for female predominance, from the general evidence of spiders, birds, etc. Lester F. Ward crystallized the arguments for this view in an article entitled "Our Better Halves" in The Forum in 1888. This philosophy of sex, which he christened the "Gynæcocentric Theory," is best known as expanded into the fourteenth chapter of his "Pure Sociology," published fifteen years later. Its publication at this late date gave it an unfortunate vitality long after its main tenets had been disproved in the biological laboratory. Germ-cell and body-cell functions were not separated. Arguments from social structures, from cosmic, natural and human history, much of it deduced by analogy, were jumbled together in a fashion which seems amazing to us now, though common enough thirty years ago. It was not a wild hypothesis in 1888, its real date, but its repeated republication (in the original and in the works of other writers who accepted it as authoritative) since 1903 has done much to discredit sociology with biologists and, what is more serious, to muddle ideas about sex and society.
In 1903, Weismann's theory of the continuity of the germplasm was ten years old. De Vries' experiments in variation and Mendel's rediscovered work on plant hybridization had hopelessly undermined the older notion that the evolution or progress of species has taken place through the inheritance of acquired characters—that is, that the individuals developed or adapted themselves to suit their surroundings and that these body-modifications were inherited by their offspring. As pointed out in Chapter I, biologists have accepted Weismann's theory of a continuous germplasm, and that this germplasm, not the body, is the carrier of inheritance. Nobody has so far produced evidence of any trace of any biological mechanism whereby development of part of the body—say the biceps of the brain—of the individual could possibly produce such a specific modification of the germplasm he carries as to result in the inheritance of a similar development by his offspring.
Mendel's experiments had shown that the characters we inherit are units or combinations of units, very difficult to permanently change or modify. They combine with each other in all sorts of complicated ways. Sometimes one will "dominate" another, causing it to disappear for a generation or more; but it is not broken up. These characters have a remarkable way of becoming "segregated" once more—that is, of appearing intact later on.
While it follows from Weismann's theory that an adaptation acquired by an individual during his lifetime cannot be transmitted to his offspring, it remained for De Vries to show authoritatively that evolution can, and does, take place without this. Once this was established, biologists cheerfully abandoned the earlier notion. Lester Ward and the biologists of his day in general not only believed in the transmission of acquired characters, but they filled the obvious gaps which occurred in trying to apply this theory to the observed facts by placing a fantastic emphasis upon sexual selection. That is, much progress was accounted for through the selection by the females of the superior males. This, as a prime factor in evolution, has since been almost "wholly discredited" (Kellogg's phrase) by the careful experiments of Mayer, Soule, Douglass, Dürigen, Morgan and others. The belief in sexual selection involved a long string of corollaries, of which biology has about purged itself, but they hang on tenaciously in sociological and popular literature. For instance, Ward believed in the tendency of opposites to mate (tall men with short women, blonds with brunettes, etc.), although Karl Pearson had published a statistical refutation in his Grammar of Science, which had run through two editions when the Pure Sociology appeared. The greater variability of males than females, another gynæcocentric dogma had also been attacked by Pearson on statistical evidence in 1897 (in the well-known essay on Variation in Man and Woman, in Chances of Death) and has become increasingly unacceptable through the researches of Mrs. Hollingworth[[6, ][7, ][8]]. The idea of a vanished age of mother-rule in human society, so essential to the complete theory, has long since been modified by anthropologists.
De Vries' experiments showed that a moderately simple fact practically makes all these complicated theories unnecessary. No two living things are exactly alike—that is, all living matter is more or less variable. Some variations are more fortunate than others, and these variants are the ones which survive—the ones best adapted to their environment. Given this fact of the constant variation of living matter, natural selection (i.e., survival of the fittest and elimination of the unfit) is the mechanism of evolution or progress which best accounts for the observed facts. Such variation is called "chance variation," not because it takes place by "chance" in the properly accepted sense of the term, but because it is so tremendously varied—is evidently due to such complicated and little-understood circumstances—that it can best be studied mathematically, using statistical applications of the "theory of probabilities."
The fine-spun, elaborate theories about sex, so current twenty years ago, have fallen into almost complete desuetude among scientists. With the discovery of the place of the chromosomes in inheritance, biologists began to give their almost undivided attention to a rigid laboratory examination of the cell. This has included sex phenomena since McClung and Sutton pointed out the function of the sex chromosome in 1902 and 1903. Present-day "theories" are little more than working hypotheses, developed, not in a library or study, but with one eye glued to a high-power microscope.
Besides its faulty foundation as to facts, the old gynæcocentric theory involved a method of treatment by historical analogy which biologists have almost entirely discarded. Anyone interested in the relative value of different kinds of biological data for social problems would do well to read the opening chapter of Prof. Morgan's "Critique of the Theory of Evolution"[[9]] , for even a summary of which space is lacking here. College reference shelves are still stocked with books on sex sociology which are totally oblivious of present-day biology. For example, Mrs Gilman (Man-Made World), Mrs Hartley (Truth About Woman) and the Nearings (Woman and Social Progress) adhere to Ward's theory in substantially its primitive form, and not even sociologists like Professor Thomas (Sex and Society) have been able to entirely break away from it.
The old question of male and female predominance in inheritance has been to a considerable extent cleared up, to the discomfiture of both sides to the controversy. Most exhaustive experiments failed to trace any characters to any other part of either sperm or egg than the nucleus. Transmission of characteristics seemed to be absolutely equal by the two parents. The male nucleus enters the egg practically naked. Hence if the characters are transmitted equally, there is certainly ground for supposing that only the nucleus of the egg has such functions, and that the remainder merely provides material for early development. Yet this does not seem to be strictly true.
Parthenogenesis (development of eggs without agency of male sperm) proves that in many simple forms the female nucleus alone possesses all the essential determiners for a new individual. Boveri's classic experiment[[10]] proved the same thing for the male nucleus. He removed the nuclei from sea-urchin eggs and replaced them with male nuclei. Normal individuals developed. To make things still more certain, he replaced the female nucleus with a male one from a different variety of sea-urchin. The resulting individual exhibited the characteristics of the male nucleus only—none of those of the species represented by the egg. Here, then, was inheritance definitely traced to the nucleus. If this nucleus is a male the characters are those of the male line; if a female those of the female line, and in sexual reproduction where the two are fused, half and half.