The chief arguments against the Theory of Natural Selection with which
Mr. Belloc has favoured us are neatly set out by him in two triads.
His passion for orderly arrangement is greater than his logic, and we
shall find that the second and third arguments of his second triad
are substantially the same. He is rather exceptionally ignorant of
modern scientific literature, and his arguments do not cover all the
countervailing considerations upon which systematic observation and
research work have been based--the speculations of Dr. Fairfield Osborn
would have been a godsend for him--but the things he has to say are
conveniently simple; they embody some prevalent misconceptions, and
they will be useful in accentuating the more salient points in my
account of the theory given in my second paper.
He produces first certain remarkable _a priori_ arguments--his “three
_a prior_ arguments.” The first is beautifully absurd. It is difficult
to believe it is advanced in anything but a spirit of burlesque.
He says that an advantage is not an advantage. He says that an
advantage does not give an advantage unless it is combined with other
advantages. You will think I am misrepresenting him. Then please read
this:--
“(1) The advantageous differences making for survival are not of
one kind in any particular case, but of an indefinitely large
number (_e.g._, climate getting colder needs not only warmer
coat, but power to digest new food, protective colouring so
as not to show dark against snow, etc., an indefinitely large
number of qualities). Now the chance of _all_ being combined
(and co-ordinated) in a single individual, _without design_,
_accidentally_, let alone of their thus appearing in many
individuals _accidentally and without design_, approximates to
zero.”
This is, so to speak, the short uncompleted form of the first argument.
It is expanded later to a copiousness too great to admit of quotation.
This expansion carries the statement right to its conclusion, that
only an individual possessing all the possible differences that
are advantageous at any particular time can survive. Otherwise its
differences have no “survival value.” They may be advantages, but
not sufficient advantages to score an advantage. I know this sounds
tipsy, but there it is in black and white in Mr. Belloc’s wonderful
Article V for any one to consult. It follows plainly that, except for a
miracle, every species must be exterminated in every generation. I can
see no other way out of it. No individual, he declares, can survive
without the full set of advantageous differences, and the chance of any
individual having the full set of advantageous differences, he declares
after some abstruse verbal gestures, is zero. There is Mr. Belloc with
his unfailing logic, his clear mathematical demonstration, and all
the rest of it. There is the lucid Latin mind shining above my Nordic
fog! Yet the previous generation got along without any of the set! And
species do survive.
Did Mr. Belloc imagine he was saying something else? It is not for me
to speculate. Helping out an antagonist in a controversy is apt to be
resented. He has, I think, simply got into a muddle here, and he is
not sufficiently self-critical to get out of it again. So he tries
to muddle through. It is quite reasonable to say that when a species
is under stress of changing conditions it is usual for the need for
adaptation to be felt upon a number of points and not simply upon
one, and that, since every advantage counts, the individuals with the
greatest combination of advantageous differences have the best chances.
But that does not alter the fact that even a single advantage is an
advantage. What happens in nature is not an extermination of all who
are not completely in the fashion of the new differences. That seems
to be Mr. Belloc’s idea, but it is a wrong idea. What does happen is
a diminution in each generation of the number of the disadvantaged
in relation to the number of the advantaged. That is quite another
affair. Mr. Belloc has not grasped this. His third _a priori_ argument
shows as much even more plainly than his first, and to that I shall
presently come.