|"Lyell's |of conditions are permanent |
|Principles of Geology." |changes, in the sense |
| |of not reverting back to |
| |identical previous conditions, |
| |the changes of organic |
| |forms must be in the |
| |same sense permanent, and |
| |thus originate SPECIES. |
|_________________________________|_________________________________|

IX.

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 of species he may have
outlived, or to the amount of terrestrial change he may have witnessed.

_Wide differences of opinion as to Man's Origin._

But while on this question of man's antiquity there is a very general
agreement,--and all are waiting eagerly for fresh evidence to clear up
those points which all admit to be full of doubt,--on other, and not
less obscure and difficult questions, a considerable amount of dogmatism
is exhibited; doctrines are put forward as established truths, no doubt
or hesitation is admitted, and it seems to be supposed that no further
evidence is required, or that any new facts