both to the body and mind. I also attributed some amount of
modification to the direct and prolonged action of changed conditions
of life. Some allowance, too, must be made for occasional reversions of
structure; nor must we forget what I have called correlated growth,
meaning, thereby, that various parts of the organisation are in some
unknown manner so connected, that when one part varies, so do others;
and if variations in the one are accumulated by selection, other parts
will be modified. Again, it has been said by several critics, that when
I found that many details of structure in man could not be explained
through natural selection, I invented sexual selection; I gave,
however, a tolerably clear sketch of this principle in the first
edition of the Origin of Species, and I there stated that it was
applicable to man. This subject of sexual selection has been treated at
full length in the present work, simply because an opportunity was here
first afforded me. I have been struck with the likeness of many of the
half-favourable criticisms on sexual selection, with those which
appeared at first on natural selection; such as, that it would explain
some few details, but certainly was not applicable to the extent to
which I have employed it. My conviction of the power of sexual
selection remains unshaken; but it is probable, or almost certain, that
several of my conclusions will hereafter be found erroneous; this can
hardly fail to be the case in the first treatment of a subject. When
naturalists have become familiar with the idea of sexual selection, it
will, as I believe, be much more largely accepted; and it has already
been fully and favourably received by several capable judges.
DOWN, BECKENHAM, KENT, September, 1874.
First Edition February 24, 1871. Second Edition September, 1874.
DETAILED TABLE OF CONTENTS
INTRODUCTION.
PART I. THE DESCENT OR ORIGIN OF MAN.
CHAPTER I.
3