And now let us come to Mr. Belloc’s second triad of arguments--his
arguments, as he calls them, “from Evidence.” The sole witness on
Evidence called is his own sturdy self. He calls himself into the box,
and I will admit he gives his testimony in a bluff, straightforward
manner--a good witness. He says very properly that the theory of
Natural Selection repudiates any absolute fixity of species. But we
have to remember that the rate of change in any species is dependent
upon the balance between that species and its conditions, and if this
remains fairly stable the species may remain for as long without
remarkable developments, or indulge in variations not conditioned
by external necessities. The classical _Lingula_ of the geological
text-books, a warm-water shell-fish, has remained much the same
creature throughout the entire record, for hundreds of millions of
years it may be. It was suited to its submarine life, and hardly any
variation was possible that was not a disadvantage. It swayed about
within narrow limits.
This admission of a practical stability annoys Mr. Belloc; it seems
to be a mean trick on the part of the Theory of Natural Selection. He
rather spoils his case by saying that “according to Natural Selection”
the swallow ought to go on flying “faster and faster with the process
of time.” Until it bursts into flames like a meteor and vanishes from
our world? And the _Lingula_ ought to become more and more quiescent
until it becomes a pebble? Yet plainly there is nothing in the Theory
of Natural Selection to make the swallow fly any faster than its needs
require. Excess of swiftness in a swallow may be as disadvantageous as
jumping to conclusions can be to a controversialist.