But in all seriousness, why should indefinite and unlimited variation
have been regarded as a more probable account of the origin of
Adaptation? Only, I think, because the obstacle was shifted one plane
back, and so looked rather less prominent. The abundance of
Adaptation, we all grant, is an immense, almost an unsurpassable
difficulty in all non-Lamarckian views of Evolution; but if the steps
by which that adaptation arose were fortuitious, to imagine them
insensible is assuredly no help. In one most important respect indeed,
as has often been observed, it is a multiplication of troubles. For
the smaller the steps, the less could Natural Selection act upon them.
Definite variations--and of the occurrence of definite variations in
abundance we have now the most convincing proof--have at least the
obvious merit that they can make and often do make a real difference
in the chances of life.
There is another aspect of the Adaptation problem to which I can
allude very briefly. May not our present ideas of the universality and
precision of Adaptation be greatly exaggerated? The fit of organism to
its environment is not after all so very close--a proposition
unwelcome perhaps, but one which could be illustrated by very copious
evidence. Natural Selection is stern, but she has her tolerant moods.
We have now most certain and irrefragable proof that much definiteness
exists in living things apart from Selection, and also much that may
very well have been preserved and so in a sense constituted by
Selection. Here the matter is likely to rest. There is a passage in
the sixth edition of the _Origin_ which has I think been overlooked.
On page 70 Darwin says, "The tuft of hair on the breast of the wild
turkey-cock cannot be of any use, and it is doubtful whether it can be
ornamental in the eyes of the female bird." This tuft of hair is a
most definite and unusual structure, and I am afraid that the remark
that it "cannot be of any use" may have been made inadvertently; but
it may have been intended, for in the first edition the usual
qualification was given and must therefore have been deliberately
excised. Anyhow I should like to think that Darwin did throw over that
tuft of hair, and that he felt relief when he had done so. Whether
however we have his great authority for such a course or not, I feel
quite sure that we shall be rightly interpreting the facts of nature
if we cease to expect to find purposefulness wherever we meet with
definite structures or patterns. Such things are, as often as not, I
suspect rather of the nature of tool-marks, mere incidents of
manufacture, benefiting their possessor not more than the wire-marks
in a sheet of paper, or the ribbing on the bottom of an oriental plate
renders those objects more attractive in our eyes.
Public-domain text, read in full here on John Shaqi.
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