The slighter the inner differences in an ethnic stock, whether in culture, language or physical traits, the smaller was their center of distribution and the more rapid their dispersal. The small initial habitat restricts the chances of variation through isolation and contrasted geographic conditions, as does also the short duration of their subsequent separation. The amazing uniformity of the Eskimo type from Bering Strait to eastern Greenland can only thus be explained, even after making allowance for the monotony of their geographic conditions and remoteness from outside influences. The distribution of the Bantu dialects over so wide a region in Central Africa and with such slight divergences presupposes narrow limits both of space and time for their origin, and a short period since their dispersal.[237] Small centers of dispersion are generally natural districts with fixed boundaries, favored by their geographical location or natural resources or by both for the development of a relatively dense population. When this increases beyond the local limits of subsistence, there follows an emigration in point of number and duration out of all proportion to the small area whence it issues. Ancient Phoenicia, Crete, Samos, mediaeval Norway, Venice, Yemen, modern Malta, Gilbert Islands, England and Japan furnish examples. Such small favored areas, when they embody also strong political power, may get the start in the occupation of colonial lands. This gives them a permanent advantage, if their colonies are chosen with a view to settlement in congenial climates, as were those of the English, rather than the more ephemeral advantage of trade, as were those of the Dutch and Portuguese in the Tropics. It seems also essential to these centers of dispersion, that, to be effective, they must command the wide choice of outlet and destination afforded by the mighty common of the sea. Only the Inca Empire in South America gives us an example of the extensive political expansion of a small mountain state. [Sidenote: Tests of origin.]