It is notable that the fossil beds which prove the existence of an
extraordinary abundance of large mammals in North America at various
periods in the past, as well as the enormous aggregation of mammalian
life which occupied this continent, both on land and at sea, at the
time of its discovery, were confined to the Temperate and Arctic Zones.
It is popularly believed that the tropics possess an exuberance of
life beyond that of other climes, yet in no tropic lands or seas,
except in parts of Africa and southern Asia, has there been developed
such an abundance of large mammal life as these northern latitudes have
repeatedly known.
[Illustration:
From Scott’s “History of the Land Mammals of the Western Hemisphere”:
Macmillan Company
THIS REPRESENTS A SCENE AT THE CALIFORNIA ASPHALT PITS, WITH A MIRED
ELEPHANT, TWO GIANT WOLVES, AND A SABER-TOOTHED TIGER (SEE PAGE 399).]
In temperate and arctic lands such numbers of large mammals could exist
only where the vegetation not only sufficed for summer needs, but
retained its nourishing qualities through the winter. In the sea the
vast numbers of seals, sea-lions, walruses, and whales of many kinds
could be maintained only by a limitless profusion of fishes and other
marine life.
From the earliest appearance of mammals on the globe to comparatively
recent times one mammalian fauna has succeeded another in the regular
sequence of evolution, man appearing late on the scene and being
subject to the same natural influences as his mammalian kindred.
During the last few centuries, however, through the development of
agriculture, the invention of new methods of transportation, and of
modern firearms, so-called civilized man has spread over and now
dominates most parts of the earth.
As a result, aboriginal man and the large mammals of continental areas
have been, or are being, swept away and replaced by civilized man and
his domestic animals. Orderly evolution of the marvelously varied
mammal life in a state of nature is thus being brought to an abrupt
end. Henceforth fossil beds containing deposits of mammals caught
in sink-holes, and formed by river and other floods in subarctic,
temperate, and tropical parts of the earth, will contain more and more
exclusively the bones of man and his domesticated horses, cattle, and
sheep.