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

40 ON THE TEiVDENCY OF VARIETIES TO DEPART
pouter pigeons, and poodle dogs could never have
come into existence in a state of nature, because
the very first step towards such inferior forms would
have led to the rapid extinction of the race; still
less could they now exist in competition with their
wild allies. The great speed but slight endurance
of the race horse, the unwieldly strength of the
ploughman's team, would both be useless in a state
of nature. If turned wild on the pampas, such animals would probably soon become extinct, or under
favourable circumstances might each gradually lose
those extreme qualities which would never be called
into action, and in a few generations revert to a
common type, which must be that in which the
various powers and faculties are so proportioned to
each other as to be best adapted to procure food and
secure safety, —that in which by the full exercise of
every part of its organisation the animal can alone
continue to live. Domestic varieties, when turned
wild, muust return to something near the type of
the original wild stock, or become altogetliher extinct.*,
We see, then, that no inferences as to the permanence of varieties in a state of nature can be
deduced from the observations of those occurring
among domestic animals. The two are so much opposed to each other in every circumstance of their
* That is, they will vary, and the variations which tend to
adapt them to the wild state, and therefore approximate them
tX wild animals, will be preserved. Those individuals which do
not vary sufficiently will perish.