The question whether the effects of use and disuse are inherited, or, in
other words, whether acquired characters are hereditary, is of
considerable interest to the general student of evolution; but it is, or
should be, a matter of far deeper interest to the thoughtful
philanthropist who desires to ensure the permanent welfare and happiness
of the human race. So profoundly important, in fact, are the moral,
social, and political conclusions that depend on the answer to this
inquiry, that, as Mr. Herbert Spencer rightly says, it "demands, beyond
all other questions whatsoever, the attention of scientific men."
It is obvious that we can produce important changes in the individual.
We can, for example, improve his muscles by athletics, and his brain by
education. The use of organs enlarges and strengthens them; the disuse
of parts or faculties weakens them. And so great is the power of habit
that it is proverbially spoken of as "second nature." It is thus certain
that we can modify the individual. We can strengthen (or weaken) his
body; we can improve (or deteriorate) his intellect, his habits, his
morals. But there remains the still more important question which we are
about to consider. Will such modifications be inherited by the offspring
of the modified individual? Does individual improvement transmit itself
to descendants independently of personal teaching and example? Have
artificially produced changes of structure or habit any inherent
tendency to become congenitally transmissible and to be converted in
time into fixed traits of constitution or character? Can the
philanthropist rely on such a tendency as a hopeful factor in the
evolution of mankind?--the only sound and stable basis of a higher and
happier state of things being, as he knows or ought to know, the innate
and constitutionally-fixed improvement of the race as a whole. If
acquired modifications are impressed on the offspring and on the race,
the systematic moral training of individuals will in time produce a
constitutionally moral race, and we may hope to improve mankind even in
defiance of the unnatural selection by which a spurious but highly
popular philanthropy would systematically favour the survival of the
unfittest and the rapid multiplication of the worst. But if acquired
modifications do not tend to be transmitted, if the use or disuse of
organs or faculties does not similarly affect posterity by inheritance,
then it is evident that no innate improvement in the race can take place
without the aid of natural or artificial selection.
Herbert Spencer maintains that the effects of use and disuse _are_
inherited in kind, and in his _Factors of Organic Evolution_[1] he has
supported his contention with a selection of facts and reasonings which
I shall have the temerity to examine and criticize. Darwin also held the
same view, though not so strongly. And here, to prevent
misunderstanding, I may say that the admiration and reverence and
gratitude due to Darwin ought not to be allowed to interfere in the
slightest degree with the freest criticism of his conclusions. To
perfect his work by the correction of really extraneous errors is as
much a sacred duty as to study and apply the great truths he has taught.