IV

EVOLUTION AS A NATURAL PROCESS


The purpose of the discussions up to this point has been to present the
reasons drawn from the principal classes of zoölogical facts for believing
that living things have transformed naturally to become what they now are.
Even if it were possible to make an exhaustive analysis of all of the
known phenomena of animal structure, development, and fossil succession,
the complete bodies of knowledge could not make the evolutionary
explanation more real and evident than it is shown to be by the simple
facts and principles selected to constitute the foregoing outline. We have
dealt solely with the evidences as to the fact of evolution; and now,
having assured ourselves that it is worth while to so do, we may turn to
the intelligible and reasonable evidence found by science which proves
that the familiar and everyday "forces" of nature are competent to bring
about evolution if they have operated in the past as they do to-day.
Investigation has brought to light many of the subsidiary elements of the
whole process, and these are so real and obvious that they are simply
taken for granted without a suspicion on our part of their power until
science directs our attention to them.

For one reason or another, those who take up this subject for the first
time find it difficult to banish from their minds the idea that evolution,
even if it ever took place, has been ended. They think it futile to expect
that a scrutiny of to-day's order can possibly find influences powerful
enough to have any share in the marvelous process of past evolution