appears to be quite unconscious, and to introduce as a scientific
hypothesis the doctrine that man s gain of KNOWLEDGE was the cause of a
temporary but long-enduring moral deterioration as indicated by the
many foul customs, especially as to marriage, of savage tribes. What
does the Jewish tradition of the moral degeneration of man through his
snatching at a knowledge forbidden him by his highest instinct assert
beyond this? ) as to lead them regularly to destroy their own
offspring, or to be quite devoid of jealousy. There would have been no
prudential restraint from marriage, and the sexes would have freely
united at an early age. Hence the progenitors of man would have tended
to increase rapidly; but checks of some kind, either periodical or
constant, must have kept down their numbers, even more severely than
with existing savages. What the precise nature of these checks were, we
cannot say, any more than with most other animals. We know that horses
and cattle, which are not extremely prolific animals, when first turned
loose in South America, increased at an enormous rate. The elephant,
the slowest breeder of all known animals, would in a few thousand years
stock the whole world. The increase of every species of monkey must be
checked by some means; but not, as Brehm remarks, by the attacks of
beasts of prey. No one will assume that the actual power of
reproduction in the wild horses and cattle of America, was at first in
any sensible degree increased; or that, as each district became fully
stocked, this same power was diminished. No doubt, in this case, and in
all others, many checks concur, and different checks under different
circumstances; periodical dearths, depending on unfavourable seasons,
being probably the most important of all. So it will have been with the
early progenitors of man.
NATURAL SELECTION.
We have now seen that man is variable in body and mind; and that the
variations are induced, either directly or indirectly, by the same
general causes, and obey the same general laws, as with the lower
animals. Man has spread widely over the face of the earth, and must
have been exposed, during his incessant migrations (63. See some good
remarks to this effect by W. Stanley Jevons, A Deduction from Darwin s
Theory, Nature, 1869, p. 231.), to the most diversified conditions.
The inhabitants of Tierra del Fuego, the Cape of Good Hope, and
Tasmania in the one hemisphere, and of the arctic regions in the other,
must have passed through many climates, and changed their habits many
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