Introduction

  THE NATURE of the following work will be best understood by a
brief account of how it came to be written. During many years I
collected notes on the origin or descent of man, without any intention
of publishing on the subject, but rather with the determination not to
publish, as I thought that I should thus only add to the prejudices
against my views. It seemed to me sufficient to indicate, in the first
edition of my Origin of Species, that by this work "light would be
thrown on the origin of man and his history"; and this implies that
man must be included with other organic beings in any general
conclusion respecting his manner of appearance on this earth. Now
the case wears a wholly different aspect. When a naturalist like
Carl Vogt ventures to say in his address as President of the
National Institution of Geneva (1869), "personne, en Europe au
moins, n'ose plus soutenir la creation independante et de toutes
pieces, des especes," it is manifest that at least a large number of
naturalists must admit that species are the modified descendants of
other species; and this especially holds good with the younger and
rising naturalists. The greater number accept the agency of natural
selection; though some urge, whether with justice the future must
decide, that I have greatly overrated its importance. Of the older and
honoured chiefs in natural science, many unfortunately are still
opposed to evolution in every form.
  In consequence of the views now adopted by most naturalists, and
which will ultimately, as in every other case, be followed by others
who are not scientific, I have been led to put together my notes, so
as to see how far the general conclusions arrived at in my former
works were applicable to man. This seemed all the more desirable, as I
had never deliberately applied these views to a species taken
singly. When we confine our attention to any one form, we are deprived
of the weighty arguments derived from the nature of the affinities
which connect together whole groups of organisms- their geographical
distribution in past and present times, and their geological
succession. The homological structure, embryological development,
and rudimentary organs of a species remain to be considered, whether
it be man or any other animal, to which our attention may be directed;
but these great classes of facts afford, as it appears to me, ample
and conclusive evidence in favour of the principle of gradual
evolution. The strong support derived from the other arguments should,
however, always be kept before the mind.
  The sole object of this work is to consider, firstly, whether man,
like every other species, is descended from some pre-existing form;
secondly, the manner of his development; and thirdly, the value of the
differences between the so-called races of man. As I shall confine
myself to these points, it will not be necessary to describe in detail
the differences between the several races- an enormous subject which
has been fully discussed in many valuable works. The high antiquity of
man has recently been demonstrated by the labours of a host of eminent
men, beginning with M. Boucher de Perthes; and this is the
indispensable basis for understanding his origin. I shall,
therefore, take this conclusion for granted, and may refer my
readers to the admirable treatises of Sir Charles Lyell, Sir John
Lubbock, and others. Nor shall I have occasion to do more than to
allude to the amount of difference between man and the
anthropomorphous apes; for Prof. Huxley, in the opinion of most
competent judges, has conclusively shewn that in every visible
character man differs less from the higher apes, than these do from
the lower members of the same order of primates.
  This work contains hardly any original facts in regard to man; but
as the conclusions at which I arrived, after drawing up a rough draft,
appeared to me interesting, I thought that they might interest others.
It has often and confidently been asserted, that man's origin can
never be known: but ignorance more frequently begets confidence than
does knowledge: it is those who know little, and not those who know
much, who so positively assert that this or that problem will never be
solved by science. The conclusion that man is the co-descendant with
other species of some ancient, lower, and extinct form, is not in
any degree new. Lamarck long ago came to this conclusion, which has
lately been maintained by several eminent naturalists and
philosophers; for instance, by Wallace, Huxley, Lyell, Vogt,
Lubbock, Buchner, Rolle, &c.,* and especially by Haeckel. This last
naturalist, besides his great work, Generelle Morphologie (1866),
has recently (1868, with a second edit. in 1870), published his
Naturliche Schopfungsgeschichte, in which he fully discusses the
genealogy of man. If this work had appeared before my essay had been
written, I should probably never have completed it. Almost all the
conclusions at which I have arrived I find confirmed by this
naturalist, whose knowledge on many points is much fuller than mine.
Wherever I have added any fact or view from Prof. Haeckel's
writings, I give his authority in the text; other statements I leave
as they originally stood in my manuscript, occasionally giving in
the foot-notes references to his works, as a confirmation of the
more doubtful or interesting points.

  * As the works of the first-named authors are so well known, I
need not give the titles; but as those of the latter are less well
known in England, I will give them:- Sechs Vorlesungen uberdie
Darwin'sche Theorie: zweite Auflage, 1868, von Dr. L. Buchner;
translated into French under the title Conferences sur la Theorie
Darwinienne, 1869. Der Mensch, im Lichte der Darwin'schen Lehre, 1865,
von Dr. F. Rolle. I will not attempt to give references to all the
authors who have taken the same side of the question. Thus G.
Canestrini has published (Annuario della Soc. dei Naturalisti, Modena,
1867, p. 81) a very curious paper on rudimentary characters, as
bearing on the origin of man. Another work has (1869) been published
by Dr. Francesco Barrago, bearing in Italian the title of "Man, made
in the image of God, was also made in the image of the ape."

  During many years it has seemed to me highly probable that sexual
selection has played an important part in differentiating the races of
man; but in my Origin of Species I contented myself by merely alluding
to this belief. When I came to apply this view to man, I found it
indispensable to treat the whole subject in full detail.* Consequently
the second part of the present work, treating of sexual selection, has
extended to an inordinate length, compared with the first part; but
this could not be avoided.

  * Prof. Haeckel was the only author who, at the time when this
work first appeared, had discussed the subject of sexual selection,
and had seen its full importance, since the publication of the Origin;
and this he did in a very able manner in his various works.

  I had intended adding to the present volumes an essay on the
expression of the various emotions by man and the lower animals. My
attention was called to this subject many years ago by Sir Charles
Bell's admirable work. This illustrious anatomist maintains that man
is endowed with certain muscles solely for the sake of expressing
his emotions. As this view is obviously opposed to the belief that man
is descended from some other and lower form, it was necessary for me
to consider it. I likewise wished to ascertain how far the emotions
are expressed in the same manner by the different races of man. But
owing to the length of the present work, I have thought it better to
reserve my essay for separate publication.