The knowledge of the history of this development is, however, comparatively new. As little as the myth of the Creation of the World--as taught us by the Bible--can be upheld in sight of the investigations of geographers and, scientists, grounded as these investigations are upon unquestionable and innumerable facts, just so untenable has its myth proved concerning the creation and evolution of man. True enough, as yet the veil is far from being lifted from all the sub-departments of this historical development of mankind; over many, on which already light has been shed, differences of opinion still exist among the investigators on the meaning and connection of this or that fact; nevertheless, on the whole, there is agreement and clearness. It is established that man did not, like the first human couple of the Bible, make his first appearance on earth in an advanced stage of civilization. He reached that plane only in the course of endlessly long lapses of time, after he had gradually freed himself from purely animal conditions, and had experienced long terms of development, in the course of which his social as well as his sexual relations--the relations between man and woman--had undergone a great variety of changes. The favorite phrase--a phrase that the ignorant or impostors daily smite our ears with on the subject of the relations between man and woman, and between the poor and the rich--"it always has been so," and the conclusion drawn therefrom--"it will always be so," _is in every sense of the word false, superficial and trumped-up_. For the purposes of this work a cursory presentation of the relations between the sexes, since primitive society, is of special importance. It is so because it can thereby be proved that, seeing that these relations have materially changed in the previous course of human development, and that the changes have taken place in even step with the existing systems of production, on the one hand, and of the distribution of the product of labor, on the other, it is natural and goes without saying that, along with further changes and revolutions in the system of production and distribution, _the relations between the sexes are bound to change again_. Nothing is "eternal," either in nature or in human life; eternal only is change and interchange.