But among the numerous obstacles and interruptions to intermixture there have been certain main barriers, such as the Atlantic Ocean, the highlands, once higher, and the now vanished seas of central Asia and the like, which have cut off great groups of varieties from other great groups of varieties over long periods of time. These separated groups of varieties developed very early certain broad resemblances and differences. Most of the varieties of men in eastern Asia and America, but not all, have now this in common, that they have yellowish buff skins, straight black hair, and often high cheek-bones. Most of the native peoples of Africa south of the Sahara, but not all, have black or blackish skins, flat noses, thick lips, and frizzy hair. In north and western Europe a great number of peoples have fair hair, blue eyes, and ruddy complexions; and about the Mediterranean there is a prevalence of white-skinned peoples with dark eyes and black hair. The black hair of many of these dark whites is straight, but never so strong and waveless as the hair of the yellow peoples. It is straighter in the east than in the west. In southern India we find brownish and darker peoples with straight black hair, and these as we pass eastward give place to more distinctly yellow peoples. In scattered islands and in Papua and New Guinea we find another series of black and brownish peoples of a more lowly type with frizzy hair. [Illustration: Australoid types] But it must be borne in mind that these are very loose-fitting generalizations. Some of the areas and isolated pockets of mankind in the Asiatic area may have been under conditions more like those in the European area; some of the African areas are of a more Asiatic and less distinctively African type. We find a wavy-haired, fairish, hairy-skinned race, the Ainu, in Japan. They are more like the Europeans in their facial type than the surrounding yellow Japanese. They may be a drifted patch of the whites or they may be a quite distinct people. We find primitive black people in the Andaman Islands far away from Australia and far away from Africa. There is a streak of very negroid blood traceable in south Persia and some parts of India. These are the “Asiatic” negroids. There is little or no proof that all black people, the Australians, the Asiatic negroids and the negroes, derive from one origin, but only that they have lived for vast periods under similar conditions. We must not assume that human beings in the eastern Asiatic area were all differentiating in one direction and all the human beings in Africa in another. There were great currents of tendency, it is true, but there were also backwaters, eddies, admixtures, readmixtures, and leakages from one main area to the other. A coloured map of the world to show the races would not present just four great areas of colour; it would have to be dabbed over with a multitude of tints and intermediate shades, simple here, mixed and overlapping there.