01 - Variations Under Domestication

01-04 - Inheritance

Any variation which is not inherited is unimportant for us.

But the number and diversity of inheritable deviations of structure, both those of slight and those of considerable physiological importance, are endless. Dr. Prosper Lucas's treatise, in two large volumes, is the fullest and the best on this subject.

No breeder doubts how strong is the tendency to inheritance; that like produces like is his fundamental belief: doubts have been thrown on this principle only by theoretical writers.

When any deviation of structure often appears, and we see it in the father and child, we cannot tell whether it may not be due to the same cause having acted on both; but when amongst individuals, apparently exposed to the same conditions, any very rare deviation, due to some extraordinary combination of circumstances, appears in the parent- say, once amongst several million individuals- and it reappears in the child, the mere doctrine of chances almost compels us to attribute its reappearance to inheritance.

Every one must have heard of cases of albinism, prickly skin, hairy bodies, &c., appearing in several members of the same family.

If strange and rare deviations of structure are really inherited, less strange and commoner deviations may be freely admitted to be inheritable.

Perhaps the correct way of viewing the whole subject would be, to look at the inheritance of every character whatever as the rule, and non-inheritance as the anomaly?

01 - Variations Under Domestication

01-04 - Inheritance

Having alluded to the subject of reversion, I may here refer to a statement often made by naturalists- namely, that our domestic varieties, when run wild, gradually but invariably revert in character to their aboriginal stocks.

Hence it has been argued that no deductions can be drawn from domestic races to species in a state of nature.

I have in vain endeavoured to discover on what decisive facts the above statement has so often and so boldly been made.

There would be great difficulty in proving its truth: we may safely conclude that very many of the most strongly marked domestic varieties could not possibly live in a wild state.

In many cases, we do not know what the aboriginal stock was, and so could not tell whether or not nearly perfect reversion had ensued. It would be necessary, in order to prevent the effects of intercrossing, that only a single variety should have been turned loose in its new home.

Nevertheless, as our varieties certainly do occasionally revert in some of their characters to ancestral forms, it seems to me not improbable that if we could succeed in naturalising, or were to cultivate, during many generations, the several races, for instance, of the cabbage, in very poor soil (in which case, however, some effect would have to be attributed to the definite action of the poor soil), that they would, to a large extent, or even wholly,
revert to the wild aboriginal stock.

cabbage

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Whether or not the experiment would succeed, is not of great importance for our line of argument; for by the experiment itself the conditions of life are changed.

Heisenberg

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If it could be shown that our domestic varieties manifested a strong tendency to reversion,- that is, to lose their acquired characters, whilst kept under the same conditions, and whilst kept in a considerable body, so that free intercrossing might check, by blending together, any slight deviations in their structure, in such case, I grant that we could deduce nothing from domestic varieties
in regard to species. But there is not a shadow of evidence in favour of this view: to assert that we could not breed our cart- and race-horses, long and short-horned cattle, and poultry of various breeds, and esculent vegetables, for an unlimited number of generations, would be opposed to all experience.

horses

cow

fowl