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Updated: May 16, 2025
In the six largest breeds the shortening of the sternum is nearly twice as great as in the three smaller breeds which remain nearest the rock-pigeon in size. We can hardly suppose that use-inheritance especially affects the eight breeds that have varied most in size. If we exclude these, there is only a total shortening of 7 per cent. to be accounted for.
In technical language, this is the problem of use-inheritance, otherwise known as the inheritance of acquired characters. It is apt to seem obvious to the plain man that the effects of use and disuse are transmitted to offspring. So, too, thought Lamarck, who half a century before Darwin propounded a theory of the origin of species that was equally evolutionary in its way.
Alcohol, tobacco, tea, coffee, extra brain work, late hours, dissipation, overwork, indoor life, division of labour, preservation of the weak, and many other causes, all help to injure the modern constitution; so that the prospect of cumulative intensification of these evils by the additional influence of use-inheritance is not an encouraging one.
If, too, the superiority of geniuses proves use-inheritance, why should not the inferiority of the sons of geniuses prove the existence of a tendency which is the exact opposite of use-inheritance? But nobody collects facts concerning the degenerate branches of musical families.
Are we to conclude that use-inheritance plus selection will modify races, just as Voltaire firmly held that incantations, together with sufficient arsenic, would destroy flocks of sheep? Is it not a significant fact that the alleged instances of use-inheritance so often prove to be self-conflicting in their details?
The trunk of the elephant, the fin of the fish, the wing of the bird, the cunning hand of man and his complicated brain and, in short, all organs and faculties whatsoever can only have been moulded and developed by use by usefulness and by using but not necessarily by use-inheritance, not necessarily by directly inherited effects of use or disuse of parts in the individual.
Broadly speaking, the adaptive effects ascribed to use-inheritance coincide with the effects of natural selection. Consequently the alleged inheritance of the advantageous effects of use and disuse cannot readily be distinguished from the similarly beneficial effects of natural selection.
Through the long stages of evolution from primæval protoplasm upwards, such species as were least affected by use-inheritance would be most free to develop necessary but seldom-used organs, protective coverings such as shells or skulls, and natural weapons, defences, ornaments, special adaptations, and so forth; and this would be an advantage for survival would obviously depend on the importance of a structure or faculty in deciding the struggle for existence and reproduction, and not on the total amount of its using or nourishment.
But use-inheritance would cumulatively alter this individual adaptability, and would tend to fix the size of organs by the average amount of ancestral use or disuse rather than by the actual requirements of the individual.
Those who accept Darwin's special explanation of the supposed inheritance of mutilations, ought to notice that his explanation applies equally well under a theory which is strongly adverse to use-inheritance namely, Galton's idea of the sterilization and complete "using up" of otherwise reproductive matter in the growth and maintenance of the personal structure.
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