[Sidenote:  Remoter sources of island populations.]

Islands do not necessarily derive their population from the land that lies nearest to them.  A comparatively narrow strait may effectively isolate, if the opposite shore is inhabited by a nautically inefficient race; whereas a wide stretch of ocean may fail to bar the immigration of a seafaring people.  Here we find a parallel to the imperfect isolation of oceanic islands for life forms endowed with superior means of dispersal, such as marine birds, bats and insects.[854] Iceland, though relatively near Greenland, was nevertheless peopled by far away Scandinavians.  These bold sailors planted their settlements even in Greenland nearly two centuries before the Eskimo.  England received the numerically dominant element of its population from across the wide expanse of the North Sea, from the bare but seaman-breeding coasts of Germany, Denmark and Norway, rather than from the nearer shores of Gaul.  So the Madeira and Cape Verde Isles had to wait for the coming of the nautical Portuguese to supply them with a population; and only later, owing to the demand for slave labor, did they draw upon the human stock of nearby Africa, but even then by means of Portuguese ships.

[Sidenote:  Double sources.]

Owing to the power of navigation to bridge the intervening spaces of water and hence to emphasize the accessibility rather than the isolation of these outlying fragments of land, we often find islands facing two or three ways, as it were, tenanted on different sides by different races, and this regardless of the width of the intervening seas, where the remote neighbors excel in nautical skill.  Formosa is divided between its wild Malay aborigines, found on the eastern, mountainous side of the island, and Chinese settlers who cultivate the wide alluvial plain on the western side.[855] Fukien Strait, though only eighty miles wide, sufficed to bar Formosa to the land-loving northern Chinese till 1644, when the island became an asylum for refugees from the Manchu invaders; but long before, the wider stretches of sea to the south and north were mere passways for the sea-faring Malays, who were the first to people the island, and the Japanese who planted considerable colonies on its northern coasts at the beginning of the fifteenth century. [See map page 103.]

In a similar way Madagascar is divided between the Malayan Hovas, who occupy the eastern and central part of the island, and the African Sakalavas who border the western coast. [See map page 105.] This distribution of the ethnic elements corresponds to that of the insect life, which is more African on the western side and more Indo-Malayan on the eastern.[856] Though the population shows every physical type between Negro and Malayan, and ethnic diversity still predominates over ethnic unity in this vast island, nevertheless the close intercourse of an island habitat has even in Madagascar produced unification of language.