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THE DESCENT OF MAN

AND

SELECTION IN RELATION TO SEX


Works by Charles Darwin, F.R.S.

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THE DESCENT OF MAN

AND

SELECTION IN RELATION TO SEX

BY

CHARLES DARWIN, M.A., F.R.S.


Uniform with this Volume

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of Favoured Races in the Struggle for Life.  Popular Edition, with a
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PREFACE TO THE SECOND EDITION.

During the successive reprints of the first edition of this work, published
in 1871, I was able to introduce several important corrections; and now
that more time has elapsed, I have endeavoured to profit by the fiery
ordeal through which the book has passed, and have taken advantage of all
the criticisms which seem to me sound.  I am also greatly indebted to a
large number of correspondents for the communication of a surprising number
of new facts and remarks.  These have been so numerous, that I have been
able to use only the more important ones; and of these, as well as of the
more important corrections, I will append a list.  Some new illustrations
have been introduced, and four of the old drawings have been replaced by
better ones, done from life by Mr. T.W. Wood.  I must especially call
attention to some observations which I owe to the kindness of Prof. Huxley
(given as a supplement at the end of Part I.), on the nature of the
differences between the brains of man and the higher apes.  I have been
particularly glad to give these observations, because during the last few
years several memoirs on the subject have appeared on the Continent, and
their importance has been, in some cases, greatly exaggerated by popular
writers.

I may take this opportunity of remarking that my critics frequently assume
that I attribute all changes of corporeal structure and mental power
exclusively to the natural selection of such variations as are often called
spontaneous; whereas, even in the first edition of the 'Origin of Species,'
I distinctly stated that great weight must be attributed to the inherited
effects of use and disuse, with respect 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.


CONTENTS.


INTRODUCTION.


PART I.  THE DESCENT OR ORIGIN OF MAN.


CHAPTER I.

The Evidence of the Descent of Man from some Lower Form.

Nature of the evidence bearing on the origin of man--Homologous structures
in man and the lower animals--Miscellaneous points of correspondence--
Development--Rudimentary structures, muscles, sense-organs, hair, bones,
reproductive organs, etc.--The bearing of these three great classes of
facts on the origin of man.


CHAPTER II.

On the Manner of Development of Man from some Lower Form.

Variability of body and mind in man--Inheritance--Causes of variability--
Laws of variation the same in man as in the lower animals--Direct action of
the conditions of life--Effects of the increased use and disuse of parts--
Arrested development--Reversion--Correlated variation--Rate of increase--
Checks to increase--Natural selection--Man the most dominant animal in the
world--Importance of his corporeal structure--The causes which have led to
his becoming erect--Consequent changes of structure--Decrease in size of
the canine teeth--Increased size and altered shape of the skull--Nakedness
--Absence of a tail--Defenceless condition of man.


CHAPTER III.

Comparison of the Mental Powers of Man and the Lower Animals.

The difference in mental power between the highest ape and the lowest
savage, immense--Certain instincts in common--The emotions--Curiosity--
Imitation--Attention--Memory--Imagination--Reason--Progressive improvement
--Tools and weapons used by animals--Abstraction, Self-consciousness--
Language--Sense of beauty--Belief in God, spiritual agencies,
superstitions.


CHAPTER IV.

Comparison of the Mental Powers of Man and the Lower Animals--continued.

The moral sense--Fundamental proposition--The qualities of social animals--
Origin of sociability--Struggle between opposed instincts--Man a social
animal--The more enduring social instincts conquer other less persistent
instincts--The social virtues alone regarded by savages--The self-regarding
virtues acquired at a later stage of development--The importance of the
judgment of the members of the same community on conduct--Transmission of
moral tendencies--Summary.


CHAPTER V.

On the Development of the Intellectual and Moral Faculties during Primeval
and Civilised times.

Advancement of the intellectual powers through natural selection--
Importance of imitation--Social and moral faculties--Their development
within the limits of the same tribe--Natural selection as affecting
civilised nations--Evidence that civilised nations were once barbarous.


CHAPTER VI.

On the Affinities and Genealogy of Man.

Position of man in the animal series--The natural system genealogical--
Adaptive characters of slight value--Various small points of resemblance
between man and the Quadrumana--Rank of man in the natural system--
Birthplace and antiquity of man--Absence of fossil connecting-links--Lower
stages in the genealogy of man, as inferred firstly from his affinities and
secondly from his structure--Early androgynous condition of the Vertebrata
--Conclusion.


CHAPTER VII.

On the Races of Man.

The nature and value of specific characters--Application to the races of
man--Arguments in favour of, and opposed to, ranking the so-called races of
man as distinct species--Sub-species--Monogenists and polygenists--
Convergence of character--Numerous points of resemblance in body and mind
between the most distinct races of man--The state of man when he first
spread over the earth--Each race not descended from a single pair--The
extinction of races--The formation of races--The effects of crossing--
Slight influence of the direct action of the conditions of life--Slight or
no influence of natural selection--Sexual selection.


PART II.  SEXUAL SELECTION.


CHAPTER VIII.

Principles of Sexual Selection.

Secondary sexual characters--Sexual selection--Manner of action--Excess of
males--Polygamy--The male alone generally modified through sexual
selection--Eagerness of the male--Variability of the male--Choice exerted
by the female--Sexual compared with natural selection--Inheritance at
corresponding periods of life, at corresponding seasons of the year, and as
limited by sex--Relations between the several forms of inheritance--Causes
why one sex and the young are not modified through sexual selection--
Supplement on the proportional numbers of the two sexes throughout the
animal kingdom-- The proportion of the sexes in relation to natural
selection.


CHAPTER IX.

Secondary Sexual Characters in the Lower Classes of the Animal Kingdom.

These characters are absent in the lowest classes--Brilliant colours--
Mollusca--Annelids--Crustacea, secondary sexual characters strongly
developed; dimorphism; colour; characters not acquired before maturity--
Spiders, sexual colours of; stridulation by the males--Myriapoda.


CHAPTER X.

Secondary Sexual Characters of Insects.

Diversified structures possessed by the males for seizing the females--
Differences between the sexes, of which the meaning is not understood--
Difference in size between the sexes--Thysanura--Diptera--Hemiptera--
Homoptera, musical powers possessed by the males alone--Orthoptera, musical
instruments of the males, much diversified in structure; pugnacity;
colours--Neuroptera, sexual differences in colour--Hymenoptera, pugnacity
and odours--Coleoptera, colours; furnished with great horns, apparently as
an ornament; battles; stridulating organs generally common to both sexes.


CHAPTER XI.

Insects, continued.--Order Lepidoptera.

(Butterflies and Moths.)

Courtship of Butterflies--Battles--Ticking noise--Colours common to both
sexes, or more brilliant in the males--Examples--Not due to the direct
action of the conditions of life--Colours adapted for protection--Colours
of moths--Display--Perceptive powers of the Lepidoptera--Variability--
Causes of the difference in colour between the males and females--Mimicry,
female butterflies more brilliantly  than the males--Bright colours
of caterpillars--Summary and concluding remarks on the secondary sexual
character of insects--Birds and insects compared.


CHAPTER XII.

Secondary Sexual Characters of Fishes, Amphibians, and Reptiles.

Fishes:  Courtship and battles of the males--Larger size of the females--
Males, bright colours and ornamental appendages; other strange characters--
Colours and appendages acquired by the males during the breeding-season
alone--Fishes with both sexes brilliantly --Protective colours--The
less conspicuous colours of the female cannot be accounted for on the
principle of protection--Male fishes building nests, and taking charge of
the ova and young.  AMPHIBIANS:  Differences in structure and colour
between the sexes--Vocal organs.  REPTILES:  Chelonians--Crocodiles--
Snakes, colours in some cases protective--Lizards, battles of--Ornamental
appendages--Strange differences in structure between the sexes--Colours--
Sexual differences almost as great as with birds.


CHAPTER XIII.

Secondary Sexual Characters of Birds.

Sexual differences--Law of battle--Special weapons--Vocal organs--
Instrumental music--Love-antics and dances--Decorations, permanent and
seasonal--Double and single annual moults--Display of ornaments by the
males.


CHAPTER XIV.

Birds--continued.

Choice exerted by the female--Length of courtship--Unpaired birds--Mental
qualities and taste for the beautiful--Preference or antipathy shewn by the
female for particular males--Variability of birds--Variations sometimes
abrupt--Laws of variation--Formation of ocelli--Gradations of character--
Case of Peacock, Argus pheasant, and Urosticte.


CHAPTER XV.

Birds--continued.

Discussion as to why the males alone of some species, and both sexes of
others are brightly --On sexually-limited inheritance, as applied
to various structures and to brightly- plumage--Nidification in
relation to colour--Loss of nuptial plumage during the winter.


CHAPTER XVI.

Birds--concluded.

The immature plumage in relation to the character of the plumage in both
sexes when adult--Six classes of cases--Sexual differences between the
males of closely-allied or representative species--The female assuming the
characters of the male--Plumage of the young in relation to the summer and
winter plumage of the adults--On the increase of beauty in the birds of the
world--Protective colouring--Conspicuously  birds--Novelty
appreciated--Summary of the four chapters on birds.


CHAPTER XVII.

Secondary Sexual Characters of Mammals.

The law of battle--Special weapons, confined to the males--Cause of absence
of weapons in the female--Weapons common to both sexes, yet primarily
acquired by the male--Other uses of such weapons--Their high importance--
Greater size of the male--Means of defence--On the preference shewn by
either sex in the pairing of quadrupeds.


CHAPTER XVIII.

Secondary Sexual Characters of Mammals--continued.

Voice--Remarkable sexual peculiarities in seals--Odour--Development of the
hair--Colour of the hair and skin--Anomalous case of the female being more
ornamented than the male--Colour and ornaments due to sexual selection--
Colour acquired for the sake of protection--Colour, though common to both
sexes, often due to sexual selection--On the disappearance of spots and
stripes in adult quadrupeds--On the colours and ornaments of the
Quadrumana--Summary.


PART III.  SEXUAL SELECTION IN RELATION TO MAN, AND CONCLUSION.


CHAPTER XIX.

Secondary Sexual Characters of Man.

Differences between man and woman--Causes of such differences, and of
certain characters common to both sexes--Law of battle--Differences in
mental powers, and voice--On the influence of beauty in determining the
marriages of mankind--Attention paid by savages to ornaments--Their ideas
of beauty in women--The tendency to exaggerate each natural peculiarity.


CHAPTER XX.

Secondary Sexual Characters of Man--continued.

On the effects of the continued selection of women according to a different
standard of beauty in each race--On the causes which interfere with sexual
selection in civilised and savage nations--Conditions favourable to sexual
selection during primeval times--On the manner of action of sexual
selection with mankind--On the women in savage tribes having some power to
choose their husbands--Absence of hair on the body, and development of the
beard--Colour of the skin--Summary.


CHAPTER XXI.

General Summary and Conclusion.

Main conclusion that man is descended from some lower form--Manner of
development--Genealogy of man--Intellectual and moral faculties--Sexual
selection--Concluding remarks.


SUPPLEMENTAL NOTE.


INDEX.



THE DESCENT OF MAN; AND SELECTION IN RELATION TO SEX.

...

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'