Even Mr. Wallace did not appreciate the full significance of this principle. The conscious adoption of a natural fact, of an observation from nature, or an assumed observation from nature, for social purposes, is an altogether different thing from the unconscious knowledge which man might have been possessed of, but which he never put to any use in his social development. Anthropologists must note not the natural facts known to later man or known to science, but the facts, or assumed facts, which early man consciously adopted for his purpose during the long period of his development from savage to civilised forms of life. The unconscious acts of mankind are of no use, or of very little use. It is only the conscious acts that will lead us along the lines of man's development. Man did not begin to build up his social system with the scientific fact of blood kinship through father and mother, but he evolved a theory of social relationship which served his purpose until the fact of blood kinship supplied a better basis. At almost the first point of origin in savage society we see man acting consciously, and it is amongst his conscious acts that we must place those traces of a sort of primitive legislation which have been found.[289] Now this being the basis of anthropological observation, we have to apply it to the question of man's earliest progress. It is at its base an economic question. Primitive economics dominated the movements and condition of early man in a far more thorough manner than modern economics affect civilisation, and between the two systems lies the whole history of man. It reveals man adapting the social unit to the productive powers of its food supply, and developing towards the adaptation of the productive powers of food supply to the social unit. In the various stages that accompany this great change, there is no defined separation of peoples according to stages of culture, savage, barbaric, or civilised. There is nothing to suggest that all peoples do not come from one centre of human life. On the contrary, the evidence is strong that the primal stages in human evolution are traceable in all the culture stages, and, therefore, that they fit in with the general conclusions of anthropologists and naturalists as to man's origin in one definite centre, and his gradual spreading out from that centre. I will take the chief conclusions arrived at in respect of this condition of birth at one centre and subsequent spreading out. Darwin has summarised the problem between the monogenists and polygenists in a manner which still ranks as a sufficient statement of the case, and his conclusion that "all the races of man are descended from a single primitive stock"[290] is accepted by the most prominent naturalists,[291] and confirmed by recent discoveries, which go to prove that this primitive stock began in miocene or pliocene times in the Indo-Malaysian intertropical lands.[292]