[On the Origin of Species by Charles Darwin]@TWC D-Link book
On the Origin of Species

CHAPTER VII
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According to our experience, abrupt and strongly marked variations occur in our domesticated productions, singly and at rather long intervals of time.

If such occurred under nature, they would be liable, as formerly explained, to be lost by accidental causes of destruction and by subsequent intercrossing; and so it is known to be under domestication, unless abrupt variations of this kind are specially preserved and separated by the care of man.

Hence, in order that a new species should suddenly appear in the manner supposed by Mr.Mivart, it is almost necessary to believe, in opposition to all analogy, that several wonderfully changed individuals appeared simultaneously within the same district.

This difficulty, as in the case of unconscious selection by man, is avoided on the theory of gradual evolution, through the preservation of a large number of individuals, which varied more or less in any favourable direction, and of the destruction of a large number which varied in an opposite manner.
That many species have been evolved in an extremely gradual manner, there can hardly be a doubt.

The species and even the genera of many large natural families are so closely allied together that it is difficult to distinguish not a few of them.


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