Project Gutenberg #1228
On the Origin of Species
Charles Darwin
1859Darwin's argument for descent with modification and natural selection, prepared chapter by chapter from Project Gutenberg HTML.
Project Gutenberg #1228 Public domain in the United States Cover source Local typographic cover created for MojiMori from public-domain source metadata
32
words at B2 or above
A1
A2
B1
B2
C1
C2
C2+
highlighted
at or above your level
AI Summary
Chapter 6 — Laws of Variation Central question What governs variation itself, and what limits our ability to predict it? Main argument Darwin surveys the imperfectly understood laws that shape variation: use and...
the allied species, must have gone through an extraordinary amount of modification since the genus arose; and thus we can understand why it should often still be variable in a much higher degree than other parts; for variation is a long-continued and slow process, and natural selection will in such cases not as yet have had time to overcome the tendency to further variability and to reversion to a less modified state. But when a species with any extraordinarily-developed organ has become the parent of many modified descendants - which on my view must be a very slow process, requiring a long lapse of time - in this case, natural selection may readily have succeeded in giving a fixed character to the organ, in however extraordinary a manner it may be developed. Species inheriting nearly the same constitution from a common parent and exposed to similar influences will naturally tend to present analogous variations, and these same species may occasionally revert to some of the characters of their ancient progenitors. Although new and important modifications may not arise from reversion and analogous variation, such modifications will add to the beautiful and harmonious diversity of nature.
Whatever the cause may be of each slight difference in the offspring from their parents - and a cause for each must exist - it is the steady accumulation, through natural selection, of such differences, when beneficial to the individual, that gives rise to all the more important modifications of structure, by which the innumerable beings on the face of this earth are enabled to struggle with each other, and the best adapted to survive.