he lack of hard stone, especially of
flint, native utensils and weapons have to be fashioned out of wood,
bones, shells, and sharks' teeth.[931]

[Sidenote: Poverty of alluvial lowlands in islands.]

Nor does the geographical limitation end here. Islands have
proportionately a scanter allowance of fertile alluvial lowlands than
have continents. This follows from their geological history, except in
the case of those low deposit islands built up from the waste of the
land. Most islands are summits of submerged mountain ranges, like
Corsica and Sardinia, the Aegean archipelagoes, the Greater Antilles,
Vancouver, and the countless fiord groups; or they are single or
composite volcanic cones, like the Canaries, Azores, Lipari, Kurile,
Fiji, Ascension, St. Helena and the Lesser Antilles; or they are a
combination of highland subsidence and volcanic out-thrust, like Japan,
the Philippines, the long Sunda chain and Iceland. Both geologic
histories involve high reliefs, steep slopes, a deep surrounding sea,
and hence rarely a shallow continental shelf for the accumulation of
broad alluvial lowlands. Among the Aegean Isles only Naxos has a flood
plain; all the rest have steep coasts, with few sand or gravel beaches,
and only small deposit plains at the head of deep and precipitous
embayments. Japan's area of arable soil is to-day only 15.7 per cent. of
its total surface, even after the gentler slopes of its mountains have
been terraced up two thousand feet. Some authorities put the figure
lower, at 10 and 12 per cent.

[Sidenote: Dense populations of islands.]

Yet in spite of limited area and this paucity of local resources,
islands constantly surprise us by their relatively dense populations.
More often than not they show a density exceeding that of the nearest
mainland having the same zonal location, often the same geologic
structure and soil. Along with other small, naturally defined areas,
they tend to a closer packing of the population. Yet side by side with
this relative over-population, we find other islands uninhabited or
tenanted only by sheep, goats and cattle.

In the wide Pacific world comprising Australia and Oceanica, islands
take up fifteen per cent. of the total land area, but they contain
forty-four per cent. of the population.[932] The insular empire of
Japan, despite the paucity of its arable soil, has a density of
population nearly twice that of China, nearly three times that of Korea,
and exceeding tha