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1859
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1859
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1 blocks not present in 1860 1861 1866 1869; present in 1859 1872
all our dogs have descended from any one wild species; but, in the case of some other domestic races, there is presumptive, or even strong, evidence in favour of this view.

some 1860 1861 1866
strongly marked races in some 1869
strongly marked races of some 1872

the breeds have 1860 1861 1866
are 1869 1872

vary on an average 1859 1860 1861
on an average vary 1866 1869 1872

I do not think 1859 1860
OMIT 1861 1866 1869 1872

offspring of any single species, then such facts would have great weight in making us doubt about the immutability of the many
very
very
closely allied
and
....
natural species — for instance, of the many foxes — inhabiting different quarters of the world. I do not believe, as we shall presently see, that the whole amount of difference between the several breeds of the dog has been produced under domestication; I believe that some small part of the difference is due to their
having
being
descended from distinct species. In the case of some other domesticated species, there is
presumptive
presumptive,
or even strong evidence, that all the breeds have descended from a single wild stock.
It has often been assumed that man has chosen for domestication animals and plants having an extraordinary inherent tendency to vary, and likewise to withstand diverse climates. I do not dispute that these capacities have added largely to the value of most of our domesticated productions; but how could a savage possibly know, when he first tamed an animal, whether it would vary in succeeding generations, and whether it would endure other climates? Has the little variability of the ass
and goose,
or guinea-fowl,
or the small power of endurance of warmth by the
rein-deer,
reindeer,
or of cold by the common
camel
camel,
prevented their domestication? I cannot doubt that if other animals and plants, equal in number to our domesticated productions, and belonging to equally diverse classes and countries, were taken from a state of nature, and could be made to breed for an equal number of generations under domestication, they would vary on an average as largely as the parent species of our existing domesticated productions have varied.
In the case of most of our anciently domesticated animals and plants, I do not think it is
not possible
possible
to come to any definite conclusion, whether they
are
have
descended from one or several
species.
wild species.
The argument mainly relied on by those who believe in the multiple origin