ty as well as quantity, to man as well as to brute. In
the island continent of Australia, the native mammalia, excepting some
bats, a few rodents, and a wild dog, all belong to the primitive
marsupial sub-class; its human life, at the time of the discovery, was
restricted to one retarded negroid race, showing in every part of the
island a monotonous, early Stone Age development. The sparsely scattered
oceanic islands of the Atlantic, owing to excessive isolation, were all,
except the near-lying Canaries, uninhabited at the time of their
discovery; and the Canary Islanders showed great retardation as compared
with their parent stock of northern Africa. [See map page 105.]

[Sidenote: Endemic forms.]

Despite this general poverty of species, island life is distinguished by
a great proportion of peculiar or endemic forms, and a tendency toward
divergence, which is the effect of isolation and which becomes marked in
proportion to the duration and effectiveness of isolation. Isolation, by
reducing or preventing the intercrossing which holds the individual true
to the normal type of the species, tends to produce divergences.[815]
Hence island life is more or less differentiated from that of the
nearest mainland, according to the degree of isolation. Continental
islands, lying near the coast, possess generally a flora and fauna to a
large extent identical with that of the mainland, and show few endemic
species and genera; whereas remote oceanic islands, which isolation has
claimed for its own, are marked by intense specialization and a high
percentage of species and even genera found nowhere else.[816] Even a
narrow belt of dividing sea suffices to loosen the bonds of kinship.
Recent as are the British Isles and near the Continent, they show some
biological diversity from the mainland and from each other.[817]

[Sidenote: Paradoxical influences of island habitats upon man.]

The influence of an island habitat upon its human occupants resembles
that upon its flora and fauna, but is less marked. The reason for this
is twofold. The plant and animal life are always the older and therefore
have longer felt the effects of isolation; hence they bear its stamp in
an intensified degree. Man, as a later comer, shows closer affinity to
his kin in the great cosmopolitan areas of the continents. More than
this, by reason of his inventiveness and his increasing skill in
navigation, he finds his sea boundary less strictly drawn, and theref