Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

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THE DEVELOPMENT OF HUMAN RACES
UNDER THE LAW OF NATURAL SELECTION.
AMONG the most advanced students of man, there exists
a wide difference of opinion on some of the most vital
questions respecting his nature and origin. Anthropologists are now, indeed, pretty well agreed that man
is not a recent introduction into the earth. All who
have studied the question, now admit that his antiquity is very great; and that, though we have to some
extent ascertained the minimum of time during which
he must have existed, we have made no approximation
towards determining that far greater period during
which he may have, and probably has existed. We
can with tolerable certainty affirm that man must have
inhabited the earth a thousand centuries ago, but we
cannot assert that he positively did not exist, or that
there is any good evidence against his having existed,
for a period of ten thousand centuries. We know
positively, that he was contemporaneous with many
now extinct animals, and has survived changes of the
earth's surface fifty or a hundred times greater than
any that have occurred during the historical period;
but we cannot place any definite limit to the number