All the land north of this irregular line belongs to the Hamito-Semitic section of the Caucasic division, all south of it to the western (African) section of the Ulotrichous division. Throughout this region--which comprises the whole of Sudan from the Atlantic to the White Nile, and all south of Sudan except Abyssinia, Galla, Somali and Masai lands--the African Negro, clearly, distinguished from the other main groups by the above summarised physical[130] and mental qualities, largely predominates everywhere and in many places exclusively. The route by which he probably reached these intertropical lands, where he may be regarded as practically indigenous, has been indicated in _Ethnology_, Chs. X. and XI. As regards the date of this occupation, nothing can be clearly proved. "The history of Africa reaches back but a short distance, except, of course, as far as the lower Nile Valley and Roman Africa is concerned; elsewhere no records exist, save tribal traditions, and these only relate to very recent events. Even archaeology, which can often sketch the main outlines of a people's history, is here practically powerless, owing to the insufficiency of data. It is true that stone implements of palaeolithic and neolithic types are found sporadically in the Nile Valley[131], Somaliland, on the Zambesi, in Cape Colony and the northern portions of the Congo Free State, as well as in Algeria and Tunisia; but the localities are far too few and too widely separated to warrant the inference that they are to be in any way connected. Moreover, where stone implements are found they are, as a rule, very near, even actually on, the surface of the earth," and they are rarely, if ever, found in association with bones of extinct animals. "Nothing occurs resembling the regular stratification of Europe, and consequently no argument based on geological grounds is possible[132]." The exceptions are the lower Nile and Zambesi where true palaeoliths have been found not only on the surface (which in this case is not inconsistent with great antiquity) but also in stratified gravel. Implements of palaeolithic _type_ are doubtless common, and may be compared to Chellean, Mousterian and even Solutrian specimens[133], but primitive culture is not necessarily pleistocene. Ancient forms persisted in Egypt down to the historic period, and even patination is no sure test of age, so until further evidence is found the antiquity of man in Africa must remain undecided[134].