had each species created in pairs, while others require
nations to have at once sprung into existence, and that there is no
stability or consistency in any doctrine but that of one primitive
stock.

The advocates of the original diversity of man, on the other hand, have
much to say for themselves. They argue that proofs of change in man have
never been brought forward except to the most trifling amount, while
evidence of his permanence meets us everywhere. The Portuguese and
Spaniards, settled for two or three centuries in South America, retain
their chief physical, mental, and moral characteristics; the Dutch boers
at the Cape, and the descendants of the early Dutch settlers in the
Moluccas, have not lost the features or the colour of the Germanic
races; the Jews, scattered over the world in the most diverse climates,
retain the same characteristic lineaments everywhere; the Egyptian
sculptures and paintings show us that, for at least 4000 or 5000 years,
the strongly contrasted features of the Negro and the Semitic races have
remained altogether unchanged; while more recent discoveries prove, that
the mound-builders of the Mississippi valley, and the dwellers on
Brazilian mountains, had, even in the very infancy of the human race,
some traces of the same peculiar and characteristic type of cranial
formation that now distinguishes them.

If we endeavour to decide impartially on the merits of this difficult
controversy, judging solely by the evidence that each party has brought
forward, it certainly seems that the best of the argument is on the
side of those who maintain the primitive diversity of man. Their
opponents have not been able to refute the permanence of existing races
as far back as we can trace them, and have failed to show, in a single
case, that at any former epoch the well marked varieties of mankind
approximated more closely than they do at the present day. At the same
time this is but negative evidence. A condition of immobility for four
or five thousand years, does not preclude an advance at an earlier
epoch, and--if we can show that there are causes in nature which would
check any further physical change when certain conditions were
fulfilled--does not even render such an advance improbable, if there are
any general arguments to be adduced in its favour. Such a cause, I
believe, does exist; and I shall now endeavour to point out its nature
and its mode of operation.

_Outline of the Theory of Natu