ion, based on the uncritical measurement
of less than a thousand Negro brains as compared with eleven thousand or
more European brains. Even if future measurement prove the average Negro
brain lighter, the vast majority of Negro brain weights fall within the
same limits as the whites; and finally, "neither size nor weight of the
brain seems to be of importance" as an index of mental capacity. We may,
therefore, say with Ratzel, "There is only one species of man. The
variations are numerous, but do not go deep."[39]

To this we may add the word of the Secretary of the First Races Congress:
"We are, then, under the necessity of concluding that an impartial
investigator would be inclined to look upon the various important peoples
of the world as to all intents and purposes essentially equal in
intellect, enterprise, morality, and physique."[40]

If these conclusions are true, we should expect to see in Africa the
human drama play itself out much as in other lands, and such has actually
been the fact. At the same time we must expect peculiarities arising from
the physiography of the land--its climate, its rainfall, its deserts, and
the peculiar inaccessibility of the coast.

Three principal zones of habitation appear: first, the steppes and deserts
around the Sahara in the north and the Kalahari desert in the south;
secondly, the grassy highlands bordering the Great Lakes and connecting
these two regions; thirdly, the forests and rivers of Central and West
Africa. In the deserts are the nomads, and the Pygmies are in the forest
fastnesses. Herdsmen and their cattle cover the steppes and highlands,
save where the tsetse fly prevents. In the open forests and grassy
highlands are the agriculturists.

Among the forest farmers the village is the center of life, while in the
open steppes political life tends to spread into larger political units.
Political integration is, however, hindered by an ease of internal
communication almost as great as the difficulty of reaching outer worlds
beyond the continent. The narrow Nile valley alone presented physical
barriers formidable enough to keep back the invading barbarians of the
south, and even then with difficulty. Elsewhere communication was all too
easy. For a while the Congo forests fended away the restless, but this
only temporarily.

On the whole Africa from the Sahara to the Cape offered no great physical
barrier to the invader, and we continually have whirlwinds of invading