(5) The extraordinary variability of modern Man (considered as one species) in stature, shape of skull, size and power of brain, colour, hairiness, quality of hair, and other characters, physical and mental, may be referred chiefly to his having become adapted to various local conditions upon settling here or there for long periods of time after wandering over the world in quest of game. The settling of offshoots of the original stock in certain regions long enough for them to undergo adaptation to local circumstances is the simplest explanation of existing races: the Negro adapted to equatorial Africa; the Asiatic stock (“Mongolian”) to Central Asia; the Mediterranean race to the neighbourhood of the sea after which it is named. As to the Nordic sub-race (of the Mediterranean, we may suppose), with its fair hair and skin, it has the appearance of an Arctic beast of prey, like the Polar bear. The snow-leopard of the Himalaya is found at a midway stage of such adaptation. Some geologists and zoologists now believe that, during the Glacial Period, the climate of Northern Europe was not everywhere such as necessarily to destroy the local fauna and flora, and in that case our ancestors may for ages have maintained themselves there; or, if that was impossible (as the absence of palæolithic remains in Scandinavia seems to indicate), they may have roamed for many ages along the borders of glaciation, perhaps as far as the Pacific Coast. Chinese annals refer to fair tribes in Eastern Siberia 200 years before the Christian era;[22] and it seems requisite to imagine some extensive reservoir of mankind in order to explain the origin of the vast hordes which in prehistoric as in historical times again and again invaded Europe—hordes “which the populous North Poured ever from her frozen loins, to pass Rhene or the Danau; when her barbarous sons Came like a deluge on the South, and spread Beneath Gibraltar to the Libyan sands.” That the race was formerly fairer than it is now may be inferred from the whiteness of its children’s hair: the trait has outlived its utility. The occurrence of a fair complexion in some mountain tribes, in the Alps, _e. g._, has occasioned the conjecture that it may be due in some way to mountainous conditions,[23] of which snow might be one; but, if we suppose that the Nordic race extended during the Glacial Period into Western Europe (having already acquired its distinctive characters), a fair complexion in the Alps may be understood by supposing that, whilst the greater number of them followed the ice-sheet back to the north-east, some followed it southward up into the mountains—if the complexion is really ancient there.