A Critique of the Theory of EvolutionMorgan, Thomas Hunt
Science
A Critique of the Theory of Evolution
Morgan, Thomas Hunt
Evolution
If through a mutation a character appears that is neither advantageous nor
disadvantageous, but indifferent, the chance that it may become established
in the race is extremely small, although by good luck such a thing may
occur rarely. It makes no difference whether the character in question is a
dominant or a recessive one, the chance of its becoming established is
exactly the same. If through a mutation a character appears that has an
_injurious_ effect, however slight this may be, it has practically no
chance of becoming established.
[Illustration: FIG. 94. Evolution of elephant's trunk. (After Lull.)]
If through a mutation a character appears that has a _beneficial_ influence
on the individual, the chance that the individual will survive is
increased, not only for itself, but for all of its descendants that come to
inherit this character. It is this increase in the number of individuals
possessing a particular character, that might have an influence on the
course of evolution. This gives a better chance for improvement by several
successive steps; but not because the species is more likely to mutate
again in the same direction. An imaginary example will illustrate how this
happens: When elephants had trunks less than a foot long, the chance of
getting trunks more than one foot long was in proportion to the length of
trunks already present and to the number of individuals; but increment in
trunk length is no more likely to occur from an animal having a trunk more
than one foot long than from an animal with a shorter trunk.
The case is analogous to tossing pennies. At any stage in the game the
chance of accumulating a hundred heads is in proportion to the number of
heads already obtained, and to the number of throws still to be made. But
the number of heads obtained has no influence on the number of heads that
will appear in the next throw.
[Illustration: FIG. 95. Evolution of elephant's trunk: above Maeritherium,
in the middle Tetrabelodon (After Lancaster); below African elephants
(After Gambier Bolton).]
Owing then to this property of the germ plasm to duplicate itself in a
large number of samples not only is an opportunity furnished to an
advantageous variation to become extensively multiplied, but the presence
of a large number of individuals of a given sort prejudices the probable
future result.
The question may be raised as to whether it is desirable to call selection
a _creative_ process. There are so many supernatural and mystical
implications that hang around the term creative that one can not be too
careful in stating in what sense the term is to be used. If by creative is
meant that something is made out of nothing, then of course there is no
need for the scientist to try to answer such a question. But if by a
creative process is meant that something is made out of something else,
then there are two alternatives to be reckoned with.
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account