| WHEN we look to the individuals of the same variety or
sub-variety of our older cultivated plants and animals, one of the first
points which strikes us, is, that they generally differ much more from
each other, than do the individuals of any one species or variety in a
state of nature. When we reflect on the vast diversity of the plants and
animals which have been cultivated, and which have varied during all
ages under the most different climates and treatment, I think we are
driven to conclude that this greater variability is simply due to our
domestic productions having been raised under conditions of life not so
uniform as, and somewhat different from, those to which the
parent-species have been exposed under nature. There is, also, I think,
some probability in the view propounded by Andrew Knight, that this
variability may be partly connected with excess of food. It seems pretty
clear that organic beings must be exposed during several generations to
the new conditions of life to cause any appreciable amount of variation;
and that when the organisation has once begun to vary, it generally
continues to vary for many generations. No case is on record of a
variable being ceasing to be variable under cultivation. Our oldest
cultivated plants, such as wheat, still often yield new varieties: our
oldest domesticated animals are still capable of rapid improvement or
modification.
Chapter 1- Variation Under Domestication
Charles Darwin
The Origin of Species |
