Differences in the culture of the same period in the Eastern and Western hemispheres undoubtedly existed in consequence of the unequal endowments of the continents; but the condition of society in the corresponding status must have been, in the main, substantially similar.
The ancestors of the Grecian, Roman and German tribes passed through the stages we have indicated, in the midst of the last of which the light of history fell upon them. Their differentiation from the undistinguishable mass of barbarians did not occur, probably, earlier than the commencement of the Middle Period of barbarism. The experience of these tribes has been lost, with the exception of so much as is represented by the institutions, inventions and discoveries which they brought with them, and possessed when they first came under historical observation. The Grecian and Latin tribes of the Homeric and Romulian periods afford the highest exemplification of the Upper Status of barbarism. Their institutions were likewise pure and homogeneous, and their experience stands directly connected with the final achievement of civilization.
Commencing, then, with the Australians and Polynesians, following with the American Indian tribes, and concluding with the Roman and Grecian, who afford the highest exemplifications respectively of the six great stages of human progress, the sum of their united experiences may be supposed fairly to represent that of the human family from the Middle Status of savagery to the end of ancient civilization. Consequently, the Aryan nations will find the type of the condition of their remote ancestors, when in savagery, in that of the Australians and Polynesians; when in the Lower Status of barbarism in that of the partially Village Indians of America; and when in the Middle Status in that of the Village Indians, with which their own experience in the Upper Status directly connects. So essentially identical are the arts institutions and mode of life in the same status upon all the continents, that the archaic form of the principal domestic institutions of the Greeks and Romans must even now be sought in the corresponding institutions of the American aborigines, as will be shown in the course of this volume. This fact forms a part of the accumulating evidence tending to show that the principal institutions of mankind have been developed from a few primary germs of thought; and that the course and manner of their development was predetermined, as well as restricted within narrow limits of divergence, by the natural logic of the human mind and the necessary limitations of its powers. Progress has been found to be substantially the same in kind in tribes and nations inhabiting different and even disconnected continents, while in the same status, with deviations from uniformity in particular instances produced by special causes. The argument when extended tends to establish the unity of origin of mankind.