The Descent 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.

He who wishes to decide whether man is the modified descendant of some pre-
existing form, would probably first enquire whether man varies, however
slightly, in bodily structure and in mental faculties; and if so, whether
the variations are transmitted to his offspring in accordance with the laws
which prevail with the lower animals. Again, are the variations the
result, as far as our ignorance permits us to judge, of the same general
causes, and are they governed by the same general laws, as in the case of
other organisms; for instance, by correlation, the inherited effects of use
and disuse, etc.? Is man subject to similar malconformations, the result
of arrested development, of reduplication of parts, etc., and does he
display in any of his anomalies reversion to some former and ancient type
of structure? It might also naturally be enquired whether man, like so
many other animals, has given rise to varieties and sub-races, differing
but slightly from each other, or to races differing so much that they must
be classed as doubtful species? How are such races distributed over the
world; and how, when crossed, do they react on each other in the first and
succeeding generations? And so with many other points.

The enquirer would next come to the important point, whether man tends to
increase at so rapid a rate, as to lead to occasional severe struggles for
existence; and consequently to beneficial variations, whether in body or
mind, being preserved, and injurious ones eliminated. Do the races or
species of men, whichever term may be applied, encroach on and replace one
another, so that some finally become extinct? We shall see that all these
questions, as indeed is obvious in respect to most of them, must be
answered in the affirmative, in the same manner as with the lower animals.
But the several considerations just referred to may be conveniently
deferred for a time: and we will first see how far the bodily structure of
man shews traces, more or less plain, of his descent from some lower form.
In succeeding chapters the mental powers of man, in comparison with those
of the lower animals, will be considered.

THE BODILY STRUCTURE OF MAN.

It is notorious that man is constructed on the same general type or model
as other mammals. All the bones in his skeleton can be compared with
corresponding bones in a monkey, bat, or seal. So it is with his muscles,
nerves, blood-vessels and internal viscera. The brain, the most important
of all the organs, follows the same law, as shewn by Huxley and other
anatomists. Bischoff (1. ‘Grosshirnwindungen des Menschen,’ 1868, s. 96.
The conclusions of this author, as well as those of Gratiolet and Aeby,
concerning the brain, will be discussed by Prof. Huxley in the Appendix
alluded to in the Preface to this edition.), who is a hostile witness,
admits that every chief fissure and fold in the brain of man has its
analogy in that of the orang; but he adds that at no period of development
do their brains perfectly agree; nor could perfect agreement be expected,
for otherwise their mental powers would have been the same. Vulpian (2.
‘Lec. sur la Phys.’ 1866, page 890, as quoted by M. Dally, ‘L’Ordre des
Primates et le Transformisme,’ 1868, page 29.), remarks: “Les differences
reelles qui existent entre l’encephale de l’homme et celui des singes
superieurs, sont bien minimes. Il ne faut pas se faire d’illusions a cet
egard. L’homme est bien plus pres des singes anthropomorphes par les
caracteres anatomiques de son cerveau que ceux-ci ne le sont non seulement
des autres mammiferes, mais meme de certains quadrumanes, des guenons et
des macaques.” But it would be superfluous here to give further details on
the correspondence between man and the higher mammals in the structure of
the brain and all other parts of the body.

It may, however, be worth while to specify a few points, not directly or
obviously connected with structure, by which this correspondence or
relationship is well shewn.

Man is liable to receive from the lower animals, and to communicate to
them, certain diseases, as hydrophobia,

Hydrophobia is the fear of drinking or swimming in the water, in short, we can say when someone suffers from fear of water. This psychological condition is the previous term for rabies. Because in the late stage of this deadly disease person finds it difficult to swallow water that is why fears to drink it. click useful source to know more.

variola, the glanders, syphilis,
cholera, herpes, etc. (3. Dr. W. Lauder Lindsay has treated this subject
at some length in the ‘Journal of Mental Science,’ July 1871; and in the
‘Edinburgh Veterinary Review,’ July 1858.); and this fact proves the close
similarity (4. A Reviewer has criticised (‘British Quarterly Review,’ Oct.
1st, 1871, page 472) what I have here said with much severity and contempt;
but as I do not use the term identity, I cannot see that I am greatly in
error. There appears to me a strong analogy between the same infection or
contagion producing the same result, or one closely similar, in two
distinct animals, and the testing of two distinct fluids by the same
chemical reagent.) of their tissues and blood, both in minute structure and
composition, far more plainly than does their comparison under the best
microscope, or by the aid of the best chemical analysis. Monkeys are
liable to many of the same non-contagious diseases as we are; thus Rengger
(5. ‘Naturgeschichte der Saugethiere von Paraguay,’ 1830, s. 50.), who
carefully observed for a long time the Cebus Azarae in its native land,
found it liable to catarrh, with the usual symptoms, and which, when often
recurrent, led to consumption. These monkeys suffered also from apoplexy,
inflammation of the bowels, and cataract in the eye. The younger ones when
shedding their milk-teeth often died from fever. Medicines produced the
same effect on them as on us. Many kinds of monkeys have a strong taste
for tea, coffee, and spiritous liquors: they will also, as I have myself
seen, smoke tobacco with pleasure. (6. The same tastes are common to some
animals much lower in the scale. Mr. A. Nichols informs me that he kept in
Queensland, in Australia, three individuals of the Phaseolarctus cinereus;
and that, without having been taught in any way, they acquired a strong
taste for rum, and for smoking tobacco.) Brehm asserts that the natives of
north-eastern Africa catch the wild baboons by exposing vessels with strong
beer, by which they are made drunk. He has seen some of these animals,
which he kept in confinement, in this state; and he gives a laughable
account of their behaviour and strange grimaces. On the following morning
they were very cross and dismal; they held their aching heads with both
hands, and wore a most pitiable expression: when beer or wine was offered
them, they turned away with disgust, but relished the juice of lemons. (7.
Brehm, ‘Thierleben,’ B. i. 1864, s. 75, 86. On the Ateles, s. 105. For
other analogous statements, see s. 25, 107.) An American monkey, an
Ateles, after getting drunk on brandy, would never touch it again, and thus
was wiser than many men. These trifling facts prove how similar the nerves
of taste must be in monkeys and man, and how similarly their whole nervous
system is affected.

Man is infested with internal parasites, sometimes causing fatal effects;
and is plagued by external parasites, all of which belong to the same
genera or families as those infesting other mammals, and in the case of
scabies to the same species. (8. Dr. W. Lauder Lindsay, ‘Edinburgh Vet.
Review,’ July 1858, page 13.) Man is subject, like other mammals, birds,
and even insects (9. With respect to insects see Dr. Laycock, “On a
General Law of Vital Periodicity,” ‘British Association,’ 1842. Dr.
Macculloch, ‘Silliman’s North American Journal of Science,’ vol. XVII. page
305, has seen a dog suffering from tertian ague. Hereafter I shall return
to this subject.), to that mysterious law, which causes certain normal
processes, such as gestation, as well as the maturation and duration of
various diseases, to follow lunar periods. His wounds are repaired by the
same process of healing; and the stumps left after the amputation of his
limbs, especially during an early embryonic period, occasionally possess
some power of regeneration, as in the lowest animals. (10. I have given
the evidence on this head in my ‘Variation of Animals and Plants under
Domestication,’ vol. ii. page 15, and more could be added.)

The whole process of that most important function, the reproduction of the
species, is strikingly the same in all mammals, from the first act of
courtship by the male (11. Mares e diversis generibus Quadrumanorum sine
dubio dignoscunt feminas humanas a maribus. Primum, credo, odoratu, postea
aspectu. Mr. Youatt, qui diu in Hortis Zoologicis (Bestiariis) medicus
animalium erat, vir in rebus observandis cautus et sagax, hoc mihi
certissime probavit, et curatores ejusdem loci et alii e ministris
confirmaverunt. Sir Andrew Smith et Brehm notabant idem in Cynocephalo.
Illustrissimus Cuvier etiam narrat multa de hac re, qua ut opinor, nihil
turpius potest indicari inter omnia hominibus et Quadrumanis communia.
Narrat enim Cynocephalum quendam in furorem incidere aspectu feminarum
aliquarem, sed nequaquam accendi tanto furore ab omnibus. Semper eligebat
juniores, et dignoscebat in turba, et advocabat voce gestuque.), to the
birth and nurturing of the young. Monkeys are born in almost as helpless a
condition as our own infants; and in certain genera the young differ fully
as much in appearance from the adults, as do our children from their
full-grown parents. (12. This remark is made with respect to Cynocephalus
and the anthropomorphous apes by Geoffroy Saint-Hilaire and F. Cuvier,
‘Histoire Nat. des Mammiferes,’ tom. i. 1824.) It has been urged by some
writers, as an important distinction, that with man the young arrive at
maturity at a much later age than with any other animal: but if we look to
the races of mankind which inhabit tropical countries the difference is not
great, for the orang is believed not to be adult till the age of from ten
to fifteen years. (13. Huxley, ‘Man’s Place in Nature,’ 1863, p. 34.)
Man differs from woman in size, bodily strength, hairiness, etc., as well
as in mind, in the same manner as do the two sexes of many mammals. So
that the correspondence in general structure, in the minute structure of
the tissues, in chemical composition and in constitution, between man and
the higher animals, especially the anthropomorphous apes, is extremely
close.

EMBRYONIC DEVELOPMENT.

[Fig. 1. Shows a human embryo, from Ecker, and a dog embryo, from
Bischoff. Labelled in each are:

a. Fore-brain, cerebral hemispheres, etc.
b. Mid-brain, corpora quadrigemina.
c. Hind-brain, cerebellum, medulla oblongata.
d. Eye.
e. Ear.
f. First visceral arch.
g. Second visceral arch.
H. Vertebral columns and muscles in process of development.
i. Anterior extremities.
K. Posterior extremities.
L. Tail or os coccyx.]

Man is developed from an ovule, about the 125th of an inch in diameter,
which differs in no respect from the ovules of other animals. The embryo
itself at a very early period can hardly be distinguished from that of
other members of the vertebrate kingdom. At this period the arteries run
in arch-like branches, as if to carry the blood to branchiae which are not
present in the higher Vertebrata, though the slits on the sides of the neck
still remain (see f, g, fig. 1), marking their former position. At a
somewhat later period, when the extremities are developed, “the feet of
lizards and mammals,” as the illustrious Von Baer remarks, “the wings and
feet of birds, no less than the hands and feet of man, all arise from the
same fundamental form.” It is, says Prof. Huxley (14. ‘Man’s Place in
Nature,’ 1863, p. 67.), “quite in the later stages of development that the
young human being presents marked differences from the young ape, while the
latter departs as much from the dog in its developments, as the man does.
Startling as this last assertion may appear to be, it is demonstrably
true.”

As some of my readers may never have seen a drawing of an embryo, I have
given one of man and another of a dog, at about the same early stage of
development, carefully copied from two works of undoubted accuracy. (15.
The human embryo (upper fig.) is from Ecker, ‘Icones Phys.,’ 1851-1859,
tab. xxx. fig. 2. This embryo was ten lines in length, so that the drawing
is much magnified. The embryo of the dog is from Bischoff,
‘Entwicklungsgeschichte des Hunde-Eies,’ 1845, tab. xi. fig. 42B. This
drawing is five times magnified, the embryo being twenty-five days old.
The internal viscera have been omitted, and the uterine appendages in both
drawings removed. I was directed to these figures by Prof. Huxley, from
whose work, ‘Man’s Place in Nature,’ the idea of giving them was taken.
Haeckel has also given analogous drawings in his ‘Schopfungsgeschichte.’)

After the foregoing statements made by such high authorities, it would be
superfluous on my part to give a number of borrowed details, shewing that
the embryo of man closely resembles that of other mammals. It may,
however, be added, that the human embryo likewise resembles certain low
forms when adult in various points of structure. For instance, the heart
at first exists as a simple pulsating vessel; the excreta are voided
through a cloacal passage; and the os coccyx projects like a true tail,
“extending considerably beyond the rudimentary legs.” (16. Prof. Wyman in
‘Proceedings of the American Academy of Sciences,’ vol. iv. 1860, p. 17.)
In the embryos of all air-breathing vertebrates, certain glands, called the
corpora Wolffiana, correspond with, and act like the kidneys of mature
fishes. (17. Owen, ‘Anatomy of Vertebrates,’ vol. i. p. 533.) Even at a
later embryonic period, some striking resemblances between man and the
lower animals may be observed. Bischoff says that “the convolutions of the
brain in a human foetus at the end of the seventh month reach about the
same stage of development as in a baboon when adult.” (18. ‘Die
Grosshirnwindungen des Menschen,’ 1868, s. 95.) The great toe, as
Professor Owen remarks (19. ‘Anatomy of Vertebrates,’ vol. ii. p. 553.),
“which forms the fulcrum when standing or walking, is perhaps the most
characteristic peculiarity in the human structure;” but in an embryo, about
an inch in length, Prof. Wyman (20. ‘Proc. Soc. Nat. Hist.’ Boston, 1863,
vol. ix. p. 185.) found “that the great toe was shorter than the others;
and, instead of being parallel to them, projected at an angle from the side
of the foot, thus corresponding with the permanent condition of this part
in the quadrumana.” I will conclude with a quotation from Huxley (21.
‘Man’s Place in Nature,’ p. 65.) who after asking, does man originate in a
different way from a dog, bird, frog or fish? says, “the reply is not
doubtful for a moment; without question, the mode of origin, and the early
stages of the development of man, are identical with those of the animals
immediately below him in the scale: without a doubt in these respects, he
is far nearer to apes than the apes are to the dog.”

RUDIMENTS.

This subject, though not intrinsically more important than the two last,
will for several reasons be treated here more fully. (22. I had written a
rough copy of this chapter before reading a valuable paper, “Caratteri
rudimentali in ordine all’ origine dell’ uomo” (‘Annuario della Soc. d.
Naturalisti,’ Modena, 1867, p. 81), by G. Canestrini, to which paper I am
considerably indebted. Haeckel has given admirable discussions on this
whole subject, under the title of Dysteleology, in his ‘Generelle
Morphologie’ and ‘Schopfungsgeschichte.’) Not one of the higher animals
can be named which does not bear some part in a rudimentary condition; and
man forms no exception to the rule. Rudimentary organs must be
distinguished from those that are nascent; though in some cases the
distinction is not easy. The former are either absolutely useless, such as
the mammae of male quadrupeds, or the incisor teeth of ruminants which
never cut through the gums; or they are of such slight service to their
present possessors, that we can hardly suppose that they were developed
under the conditions which now exist. Organs in this latter state are not
strictly rudimentary, but they are tending in this direction. Nascent
organs, on the other hand, though not fully developed, are of high service
to their possessors, and are capable of further development. Rudimentary
organs are eminently variable; and this is partly intelligible, as they are
useless, or nearly useless, and consequently are no longer subjected to
natural selection. They often become wholly suppressed. When this occurs,
they are nevertheless liable to occasional reappearance through reversion–
a circumstance well worthy of attention.

The chief agents in causing organs to become rudimentary seem to have been
disuse at that period of life when the organ is chiefly used (and this is
generally during maturity), and also inheritance at a corresponding period
of life. The term “disuse” does not relate merely to the lessened action
of muscles, but includes a diminished flow of blood to a part or organ,
from being subjected to fewer alternations of pressure, or from becoming in
any way less habitually active. Rudiments, however, may occur in one sex
of those parts which are normally present in the other sex; and such
rudiments, as we shall hereafter see, have often originated in a way
distinct from those here referred to. In some cases, organs have been
reduced by means of natural selection, from having become injurious to the
species under changed habits of life. The process of reduction is probably
often aided through the two principles of compensation and economy of
growth; but the later stages of reduction, after disuse has done all that
can fairly be attributed to it, and when the saving to be effected by the
economy of growth would be very small (23. Some good criticisms on this
subject have been given by Messrs. Murie and Mivart, in ‘Transact.
Zoological Society,’ 1869, vol. vii. p. 92.), are difficult to understand.
The final and complete suppression of a part, already useless and much
reduced in size, in which case neither compensation nor economy can come
into play, is perhaps intelligible by the aid of the hypothesis of
pangenesis. But as the whole subject of rudimentary organs has been
discussed and illustrated in my former works (24. ‘Variation of Animals
and Plants under Domestication,’ vol. ii pp. 317 and 397. See also ‘Origin
of Species,’ 5th Edition p. 535.), I need here say no more on this head.

Rudiments of various muscles have been observed in many parts of the human
body (25. For instance, M. Richard (‘Annales des Sciences Nat.,’ 3rd
series, Zoolog. 1852, tom. xviii. p. 13) describes and figures rudiments of
what he calls the “muscle pedieux de la main,” which he says is sometimes
“infiniment petit.” Another muscle, called “le tibial posterieur,” is
generally quite absent in the hand, but appears from time to time in a more
or less rudimentary condition.); and not a few muscles, which are regularly
present in some of the lower animals can occasionally be detected in man in
a greatly reduced condition. Every one must have noticed the power which
many animals, especially horses, possess of moving or twitching their skin;
and this is effected by the panniculus carnosus. Remnants of this muscle
in an efficient state are found in various parts of our bodies; for
instance, the muscle on the forehead, by which the eyebrows are raised.
The platysma myoides, which is well developed on the neck, belongs to this
system. Prof. Turner, of Edinburgh, has occasionally detected, as he
informs me, muscular fasciculi in five different situations, namely in the
axillae, near the scapulae, etc., all of which must be referred to the
system of the panniculus. He has also shewn (26. Prof. W. Turner,
‘Proceedings of the Royal Society of Edinburgh,’ 1866-67, p. 65.) that the
musculus sternalis or sternalis brutorum, which is not an extension of the
rectus abdominalis, but is closely allied to the panniculus, occurred in
the proportion of about three per cent. in upwards of 600 bodies: he adds,
that this muscle affords “an excellent illustration of the statement that
occasional and rudimentary structures are especially liable to variation in
arrangement.”

Some few persons have the power of contracting the superficial muscles on
their scalps; and these muscles are in a variable and partially rudimentary
condition. M. A. de Candolle has communicated to me a curious instance of
the long-continued persistence or inheritance of this power, as well as of
its unusual development. He knows a family, in which one member, the
present head of the family, could, when a youth, pitch several heavy books
from his head by the movement of the scalp alone; and he won wagers by
performing this feat. His father, uncle, grandfather, and his three
children possess the same power to the same unusual degree. This family
became divided eight generations ago into two branches; so that the head of
the above-mentioned branch is cousin in the seventh degree to the head of
the other branch. This distant cousin resides in another part of France;
and on being asked whether he possessed the same faculty, immediately
exhibited his power. This case offers a good illustration how persistent
may be the transmission of an absolutely useless faculty, probably derived
from our remote semi-human progenitors; since many monkeys have, and
frequently use the power, of largely moving their scalps up and down. (27.
See my ‘Expression of the Emotions in Man and Animals,’ 1872, p. 144.)

The extrinsic muscles which serve to move the external ear, and the
intrinsic muscles which move the different parts, are in a rudimentary
condition in man, and they all belong to the system of the panniculus; they
are also variable in development, or at least in function. I have seen one
man who could draw the whole ear forwards; other men can draw it upwards;
another who could draw it backwards (28. Canestrini quotes Hyrtl.
(‘Annuario della Soc. dei Naturalisti,’ Modena, 1867, p. 97) to the same
effect.); and from what one of these persons told me, it is probable that
most of us, by often touching our ears, and thus directing our attention
towards them, could recover some power of movement by repeated trials. The
power of erecting and directing the shell of the ears to the various points
of the compass, is no doubt of the highest service to many animals, as they
thus perceive the direction of danger; but I have never heard, on
sufficient evidence, of a man who possessed this power, the one which might
be of use to him. The whole external shell may be considered a rudiment,
together with the various folds and prominences (helix and anti-helix,
tragus and anti-tragus, etc.) which in the lower animals strengthen and
support the ear when erect, without adding much to its weight. Some
authors, however, suppose that the cartilage of the shell serves to
transmit vibrations to the acoustic nerve; but Mr. Toynbee (29. ‘The
Diseases of the Ear,’ by J. Toynbee, F.R.S., 1860, p. 12. A distinguished
physiologist, Prof. Preyer, informs me that he had lately been
experimenting on the function of the shell of the ear, and has come to
nearly the same conclusion as that given here.), after collecting all the
known evidence on this head, concludes that the external shell is of no
distinct use. The ears of the chimpanzee and orang are curiously like
those of man, and the proper muscles are likewise but very slightly
developed. (30. Prof. A. Macalister, ‘Annals and Magazine of Natural
History,’ vol. vii. 1871, p. 342.) I am also assured by the keepers in the
Zoological Gardens that these animals never move or erect their ears; so
that they are in an equally rudimentary condition with those of man, as far
as function is concerned. Why these animals, as well as the progenitors of
man, should have lost the power of erecting their ears, we cannot say. It
may be, though I am not satisfied with this view, that owing to their
arboreal habits and great strength they were but little exposed to danger,
and so during a lengthened period moved their ears but little, and thus
gradually lost the power of moving them. This would be a parallel case
with that of those large and heavy birds, which, from ihabiting oceanic
islands, have not been exposed to the attacks of beasts of prey, and have
consequently lost the power of using their wings for flight. The inability
to move the ears in man and several apes is, however, partly compensated by
the freedom with which they can move the head in a horizontal plane, so as
to catch sounds from all directions. It has been asserted that the ear of
man alone possesses a lobule; but “a rudiment of it is found in the
gorilla” (31. Mr. St. George Mivart, ‘Elementary Anatomy,’ 1873, p. 396.);
and, as I hear from Prof. Preyer, it is not rarely absent in the negro.

[Fig. 2. Human Ear, modelled and drawn by Mr. Woolner. The projecting
point is labelled a.]

The celebrated sculptor, Mr. Woolner, informs me of one little peculiarity
in the external ear, which he has often observed both in men and women, and
of which he perceived the full significance. His attention was first
called to the subject whilst at work on his figure of Puck, to which he had
given pointed ears. He was thus led to examine the ears of various
monkeys, and subsequently more carefully those of man. The peculiarity
consists in a little blunt point, projecting from the inwardly folded
margin, or helix. When present, it is developed at birth, and, according
to Prof. Ludwig Meyer, more frequently in man than in woman. Mr. Woolner
made an exact model of one such case, and sent me the accompanying drawing.
(Fig. 2). These points not only project inwards towards the centre of the
ear, but often a little outwards from its plane, so as to be visible when
the head is viewed from directly in front or behind. They are variable in
size, and somewhat in position, standing either a little higher or lower;
and they sometimes occur on one ear and not on the other. They are not
confined to mankind, for I observed a case in one of the spider-monkeys
(Ateles beelzebuth) in our Zoological Gardens; and Mr. E. Ray Lankester
informs me of another case in a chimpanzee in the gardens at Hamburg. The
helix obviously consists of the extreme margin of the ear folded inwards;
and this folding appears to be in some manner connected with the whole
external ear being permanently pressed backwards. In many monkeys, which
do not stand high in the order, as baboons and some species of macacus (32.
See also some remarks, and the drawings of the ears of the Lemuroidea, in
Messrs. Murie and Mivart’s excellent paper in ‘Transactions of the
Zoological Society,’ vol. vii. 1869, pp. 6 and 90.), the upper portion of
the ear is slightly pointed, and the margin is not at all folded inwards;
but if the margin were to be thus folded, a slight point would necessarily
project inwards towards the centre, and probably a little outwards from the
plane of the ear; and this I believe to be their origin in many cases. On
the other hand, Prof. L. Meyer, in an able paper recently published (33.
‘Uber das Darwin’sche Spitzohr,’ Archiv fur Path. Anat. und Phys., 1871, p.
485.), maintains that the whole case is one of mere variability; and that
the projections are not real ones, but are due to the internal cartilage on
each side of the points not having been fully developed. I am quite ready
to admit that this is the correct explanation in many instances, as in
those figured by Prof. Meyer, in which there are several minute points, or
the whole margin is sinuous. I have myself seen, through the kindness of
Dr. L. Down, the ear of a microcephalous idiot, on which there is a
projection on the outside of the helix, and not on the inward folded edge,
so that this point can have no relation to a former apex of the ear.
Nevertheless in some cases, my original view, that the points are vestiges
of the tips of formerly erect and pointed ears, still seems to me probable.
I think so from the frequency of their occurrence, and from the general
correspondence in position with that of the tip of a pointed ear. In one
case, of which a photograph has been sent me, the projection is so large,
that supposing, in accordance with Prof. Meyer’s view, the ear to be made
perfect by the equal development of the cartilage throughout the whole
extent of the margin, it would have covered fully one-third of the whole
ear. Two cases have been communicated to me, one in North America, and the
other in England, in which the upper margin is not at all folded inwards,
but is pointed, so that it closely resembles the pointed ear of an ordinary
quadruped in outline. In one of these cases, which was that of a young
child, the father compared the ear with the drawing which I have given (34.
‘The Expression of the Emotions,’ p. 136.) of the ear of a monkey, the
Cynopithecus niger, and says that their outlines are closely similar. If,
in these two cases, the margin had been folded inwards in the normal
manner, an inward projection must have been formed. I may add that in two
other cases the outline still remains somewhat pointed, although the margin
of the upper part of the ear is normally folded inwards–in one of them,
however, very narrowly. [Fig.3. Foetus of an Orang(?). Exact copy of a
photograph, shewing the form of the ear at this early age.] The following
woodcut (No. 3) is an accurate copy of a photograph of the foetus of an
orang (kindly sent me by Dr. Nitsche), in which it may be seen how
different the pointed outline of the ear is at this period from its adult
condition, when it bears a close general resemblance to that of man. It is
evident that the folding over of the tip of such an ear, unless it changed
greatly during its further development, would give rise to a point
projecting inwards. On the whole, it still seems to me probable that the
points in question are in some cases, both in man and apes, vestiges of a
former condition.

The nictitating membrane, or third eyelid, with its accessory muscles and
other structures, is especially well developed in birds, and is of much
functional importance to them, as it can be rapidly drawn across the whole
eye-ball. It is found in some reptiles and amphibians, and in certain
fishes, as in sharks. It is fairly well developed in the two lower
divisions of the mammalian series, namely, in the monotremata and
marsupials, and in some few of the higher mammals, as in the walrus. But
in man, the quadrumana, and most other mammals, it exists, as is admitted
by all anatomists, as a mere rudiment, called the semilunar fold. (35.
Muller’s ‘Elements of Physiology,’ Eng. translat. 1842, vol. ii. p. 1117.
Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 260; ibid. on the Walrus,
‘Proceedings of the Zoological Society,’ November 8, 1854. See also R.
Knox, ‘Great Artists and Anatomists,’ p. 106. This rudiment apparently is
somewhat larger in Negroes and Australians than in Europeans, see Carl
Vogt, ‘Lectures on Man,’ Eng. translat. p. 129.)

The sense of smell is of the highest importance to the greater number of
mammals–to some, as the ruminants, in warning them of danger; to others,
as the Carnivora, in finding their prey; to others, again, as the wild
boar, for both purposes combined. But the sense of smell is of extremely
slight service, if any, even to the dark coloured races of men, in whom it
is much more highly developed than in the white and civilised races. (36.
The account given by Humboldt of the power of smell possessed by the
natives of South America is well known, and has been confirmed by others.
M. Houzeau (‘Etudes sur les Facultes Mentales,’ etc., tom. i. 1872, p. 91)
asserts that he repeatedly made experiments, and proved that Negroes and
Indians could recognise persons in the dark by their odour. Dr. W. Ogle
has made some curious observations on the connection between the power of
smell and the colouring matter of the mucous membrane of the olfactory
region as well as of the skin of the body. I have, therefore, spoken in
the text of the dark-coloured races having a finer sense of smell than the
white races. See his paper, ‘Medico-Chirurgical Transactions,’ London,
vol. liii. 1870, p. 276.) Nevertheless it does not warn them of danger,
nor guide them to their food; nor does it prevent the Esquimaux from
sleeping in the most fetid atmosphere, nor many savages from eating
half-putrid meat. In Europeans the power differs greatly in different
individuals, as I am assured by an eminent naturalist who possesses this
sense highly developed, and who has attended to the subject. Those who
believe in the principle of gradual evolution, will not readily admit that
the sense of smell in its present state was originally acquired by man, as
he now exists. He inherits the power in an enfeebled and so far
rudimentary condition, from some early progenitor, to whom it was highly
serviceable, and by whom it was continually used. In those animals which
have this sense highly developed, such as dogs and horses, the recollection
of persons and of places is strongly associated with their odour; and we
can thus perhaps understand how it is, as Dr. Maudsley has truly remarked
(37. ‘The Physiology and Pathology of Mind,’ 2nd ed. 1868, p. 134.), that
the sense of smell in man “is singularly effective in recalling vividly the
ideas and images of forgotten scenes and places.”

Man differs conspicuously from all the other primates in being almost
naked. But a few short straggling hairs are found over the greater part of
the body in the man, and fine down on that of the woman. The different
races differ much in hairiness; and in the individuals of the same race the
hairs are highly variable, not only in abundance, but likewise in position:
thus in some Europeans the shoulders are quite naked, whilst in others they
bear thick tufts of hair. (38. Eschricht, Uber die Richtung der Haare am
menschlichen Korper, Muller’s ‘Archiv fur Anat. und Phys.’ 1837, s. 47. I
shall often have to refer to this very curious paper.) There can be little
doubt that the hairs thus scattered over the body are the rudiments of the
uniform hairy coat of the lower animals. This view is rendered all the
more probable, as it is known that fine, short, and pale-coloured hairs on
the limbs and other parts of the body, occasionally become developed into
“thickset, long, and rather coarse dark hairs,” when abnormally nourished
near old-standing inflamed surfaces. (39. Paget, ‘Lectures on Surgical
Pathology,’ 1853, vol. i. p. 71.)

I am informed by Sir James Paget that often several members of a family
have a few hairs in their eyebrows much longer than the others; so that
even this slight peculiarity seems to be inherited. These hairs, too, seem
to have their representatives; for in the chimpanzee, and in certain
species of Macacus, there are scattered hairs of considerable length rising
from the naked skin above the eyes, and corresponding to our eyebrows;
similar long hairs project from the hairy covering of the superciliary
ridges in some baboons.

The fine wool-like hair, or so-called lanugo, with which the human foetus
during the sixth month is thickly covered, offers a more curious case. It
is first developed, during the fifth month, on the eyebrows and face, and
especially round the mouth, where it is much longer than that on the head.
A moustache of this kind was observed by Eschricht (40. Eschricht, ibid.
s. 40, 47.) on a female foetus; but this is not so surprising a
circumstance as it may at first appear, for the two sexes generally
resemble each other in all external characters during an early period of
growth. The direction and arrangement of the hairs on all parts of the
foetal body are the same as in the adult, but are subject to much
variability. The whole surface, including even the forehead and ears, is
thus thickly clothed; but it is a significant fact that the palms of the
hands and the soles of the feet are quite naked, like the inferior surfaces
of all four extremities in most of the lower animals. As this can hardly
be an accidental coincidence, the woolly covering of the foetus probably
represents the first permanent coat of hair in those mammals which are born
hairy. Three or four cases have been recorded of persons born with their
whole bodies and faces thickly covered with fine long hairs; and this
strange condition is strongly inherited, and is correlated with an abnormal
condition of the teeth. (41. See my ‘Variation of Animals and Plants
under Domestication,’ vol. ii. p. 327. Prof. Alex. Brandt has recently
sent me an additional case of a father and son, born in Russia, with these
peculiarities. I have received drawings of both from Paris.) Prof. Alex.
Brandt informs me that he has compared the hair from the face of a man thus
characterised, aged thirty-five, with the lanugo of a foetus, and finds it
quite similar in texture; therefore, as he remarks, the case may be
attributed to an arrest of development in the hair, together with its
continued growth. Many delicate children, as I have been assured by a
surgeon to a hospital for children, have their backs covered by rather long
silky hairs; and such cases probably come under the same head.

It appears as if the posterior molar or wisdom-teeth were tending to become
rudimentary in the more civilised races of man. These teeth are rather
smaller than the other molars, as is likewise the case with the
corresponding teeth in the chimpanzee and orang; and they have only two
separate fangs. They do not cut through the gums till about the
seventeenth year, and I have been assured that they are much more liable to
decay, and are earlier lost than the other teeth; but this is denied by
some eminent dentists. They are also much more liable to vary, both in
structure and in the period of their development, than the other teeth.
(42. Dr. Webb, ‘Teeth in Man and the Anthropoid Apes,’ as quoted by Dr. C.
Carter Blake in Anthropological Review, July 1867, p. 299.) In the
Melanian races, on the other hand, the wisdom-teeth are usually furnished
with three separate fangs, and are generally sound; they also differ from
the other molars in size, less than in the Caucasian races. (43. Owen,
‘Anatomy of Vertebrates,’ vol. iii. pp. 320, 321, and 325.) Prof.
Schaaffhausen accounts for this difference between the races by “the
posterior dental portion of the jaw being always shortened” in those that
are civilised (44. ‘On the Primitive Form of the Skull,’ Eng. translat.,
in ‘Anthropological Review,’ Oct. 1868, p. 426), and this shortening may, I
presume, be attributed to civilised men habitually feeding on soft, cooked
food, and thus using their jaws less. I am informed by Mr. Brace that it
is becoming quite a common practice in the United States to remove some of
the molar teeth of children, as the jaw does not grow large enough for the
perfect development of the normal number. (45. Prof. Montegazza writes to
me from Florence, that he has lately been studying the last molar teeth in
the different races of man, and has come to the same conclusion as that
given in my text, viz., that in the higher or civilised races they are on
the road towards atrophy or elimination.)

With respect to the alimentary canal, I have met with an account of only a
single rudiment, namely the vermiform appendage of the caecum. The caecum
is a branch or diverticulum of the intestine, ending in a cul-de-sac, and
is extremely long in many of the lower vegetable-feeding mammals. In the
marsupial koala it is actually more than thrice as long as the whole body.
(46. Owen, ‘Anatomy of Vertebrates,’ vol. iii. pp. 416, 434, 441.) It is
sometimes produced into a long gradually-tapering point, and is sometimes
constricted in parts. It appears as if, in consequence of changed diet or
habits, the caecum had become much shortened in various animals, the
vermiform appendage being left as a rudiment of the shortened part. That
this appendage is a rudiment, we may infer from its small size, and from
the evidence which Prof. Canestrini (47. ‘Annuario della Soc. d. Nat.’
Modena, 1867, p. 94.) has collected of its variability in man. It is
occasionally quite absent, or again is largely developed. The passage is
sometimes completely closed for half or two-thirds of its length, with the
terminal part consisting of a flattened solid expansion. In the orang this
appendage is long and convoluted: in man it arises from the end of the
short caecum, and is commonly from four to five inches in length, being
only about the third of an inch in diameter. Not only is it useless, but
it is sometimes the cause of death, of which fact I have lately heard two
instances: this is due to small hard bodies, such as seeds, entering the
passage, and causing inflammation. (48. M. C. Martins (“De l’Unite
Organique,” in ‘Revue des Deux Mondes,’ June 15, 1862, p. 16) and Haeckel
(‘Generelle Morphologie,’ B. ii. s. 278), have both remarked on the
singular fact of this rudiment sometimes causing death.)

In some of the lower Quadrumana, in the Lemuridae and Carnivora, as well as
in many marsupials, there is a passage near the lower end of the humerus,
called the supra-condyloid foramen, through which the great nerve of the
fore limb and often the great artery pass. Now in the humerus of man,
there is generally a trace of this passage, which is sometimes fairly well
developed, being formed by a depending hook-like process of bone, completed
by a band of ligament. Dr. Struthers (49. With respect to inheritance,
see Dr. Struthers in the ‘Lancet,’ Feb. 15, 1873, and another important
paper, ibid. Jan. 24, 1863, p. 83. Dr. Knox, as I am informed, was the
first anatomist who drew attention to this peculiar structure in man; see
his ‘Great Artists and Anatomists,’ p. 63. See also an important memoir on
this process by Dr. Gruber, in the ‘Bulletin de l’Acad. Imp. de St.
Petersbourg,’ tom. xii. 1867, p. 448.), who has closely attended to the
subject, has now shewn that this peculiarity is sometimes inherited, as it
has occurred in a father, and in no less than four out of his seven
children. When present, the great nerve invariably passes through it; and
this clearly indicates that it is the homologue and rudiment of the
supra-condyloid foramen of the lower animals. Prof. Turner estimates, as
he informs me, that it occurs in about one per cent. of recent skeletons.
But if the occasional development of this structure in man is, as seems
probable, due to reversion, it is a return to a very ancient state of
things, because in the higher Quadrumana it is absent.

There is another foramen or perforation in the humerus, occasionally
present in man, which may be called the inter-condyloid. This occurs, but
not constantly, in various anthropoid and other apes (50. Mr. St. George
Mivart, ‘Transactions Phil. Soc.’ 1867, p. 310.), and likewise in many of
the lower animals. It is remarkable that this perforation seems to have
been present in man much more frequently during ancient times than
recently. Mr. Busk (51. “On the Caves of Gibraltar,” ‘Transactions of the
International Congress of Prehistoric Archaeology,’ Third Session, 1869, p.
159. Prof. Wyman has lately shewn (Fourth Annual Report, Peabody Museum,
1871, p. 20), that this perforation is present in thirty-one per cent. of
some human remains from ancient mounds in the Western United States, and in
Florida. It frequently occurs in the negro.) has collected the following
evidence on this head: Prof. Broca “noticed the perforation in four and a
half per cent. of the arm-bones collected in the ‘Cimetiere du Sud,’ at
Paris; and in the Grotto of Orrony, the contents of which are referred to
the Bronze period, as many as eight humeri out of thirty-two were
perforated; but this extraordinary proportion, he thinks, might be due to
the cavern having been a sort of ‘family vault.’ Again, M. Dupont found
thirty per cent. of perforated bones in the caves of the Valley of the
Lesse, belonging to the Reindeer period; whilst M. Leguay, in a sort of
dolmen at Argenteuil, observed twenty-five per cent. to be perforated; and
M. Pruner-Bey found twenty-six per cent. in the same condition in bones
from Vaureal. Nor should it be left unnoticed that M. Pruner-Bey states
that this condition is common in Guanche skeletons.” It is an interesting
fact that ancient races, in this and several other cases, more frequently
present structures which resemble those of the lower animals than do the
modern. One chief cause seems to be that the ancient races stand somewhat
nearer in the long line of descent to their remote animal-like progenitors.

In man, the os coccyx, together with certain other vertebrae hereafter to
be described, though functionless as a tail, plainly represent this part in
other vertebrate animals. At an early embryonic period it is free, and
projects beyond the lower extremities; as may be seen in the drawing (Fig.
1.) of a human embryo. Even after birth it has been known, in certain rare
and anomalous cases (52. Quatrefages has lately collected the evidence on
this subject. ‘Revue des Cours Scientifiques,’ 1867-1868, p. 625. In 1840
Fleischmann exhibited a human foetus bearing a free tail, which, as is not
always the case, included vertebral bodies; and this tail was critically
examined by the many anatomists present at the meeting of naturalists at
Erlangen (see Marshall in Niederlandischen Archiv fur Zoologie, December
1871).), to form a small external rudiment of a tail. The os coccyx is
short, usually including only four vertebrae, all anchylosed together: and
these are in a rudimentary condition, for they consist, with the exception
of the basal one, of the centrum alone. (53. Owen, ‘On the Nature of
Limbs,’ 1849, p. 114.) They are furnished with some small muscles; one of
which, as I am informed by Prof. Turner, has been expressly described by
Theile as a rudimentary repetition of the extensor of the tail, a muscle
which is so largely developed in many mammals.

The spinal cord in man extends only as far downwards as the last dorsal or
first lumbar vertebra; but a thread-like structure (the filum terminale)
runs down the axis of the sacral part of the spinal canal, and even along
the back of the coccygeal bones. The upper part of this filament, as Prof.
Turner informs me, is undoubtedly homologous with the spinal cord; but the
lower part apparently consists merely of the pia mater, or vascular
investing membrane. Even in this case the os coccyx may be said to possess
a vestige of so important a structure as the spinal cord, though no longer
enclosed within a bony canal. The following fact, for which I am also
indebted to Prof. Turner, shews how closely the os coccyx corresponds with
the true tail in the lower animals: Luschka has recently discovered at the
extremity of the coccygeal bones a very peculiar convoluted body, which is
continuous with the middle sacral artery; and this discovery led Krause and
Meyer to examine the tail of a monkey (Macacus), and of a cat, in both of
which they found a similarly convoluted body, though not at the extremity.

The reproductive system offers various rudimentary structures; but these
differ in one important respect from the foregoing cases. Here we are not
concerned with the vestige of a part which does not belong to the species
in an efficient state, but with a part efficient in the one sex, and
represented in the other by a mere rudiment. Nevertheless, the occurrence
of such rudiments is as difficult to explain, on the belief of the separate
creation of each species, as in the foregoing cases. Hereafter I shall
have to recur to these rudiments, and shall shew that their presence
generally depends merely on inheritance, that is, on parts acquired by one
sex having been partially transmitted to the other. I will in this place
only give some instances of such rudiments. It is well known that in the
males of all mammals, including man, rudimentary mammae exist. These in
several instances have become well developed, and have yielded a copious
supply of milk. Their essential identity in the two sexes is likewise
shewn by their occasional sympathetic enlargement in both during an attack
of the measles. The vesicula prostatica, which has been observed in many
male mammals, is now universally acknowledged to be the homologue of the
female uterus, together with the connected passage. It is impossible to
read Leuckart’s able description of this organ, and his reasoning, without
admitting the justness of his conclusion. This is especially clear in the
case of those mammals in which the true female uterus bifurcates, for in
the males of these the vesicula likewise bifurcates. (54. Leuckart, in
Todd’s ‘Cyclopaedia of Anatomy’ 1849-52, vol. iv. p. 1415. In man this
organ is only from three to six lines in length, but, like so many other
rudimentary parts, it is variable in development as well as in other
characters.) Some other rudimentary structures belonging to the
reproductive system might have been here adduced. (55. See, on this
subject, Owen, ‘Anatomy of Vertebrates,’ vol. iii. pp. 675, 676, 706.)

The bearing of the three great classes of facts now given is unmistakeable.
But it would be superfluous fully to recapitulate the line of argument
given in detail in my ‘Origin of Species.’ The homological construction of
the whole frame in the members of the same class is intelligible, if we
admit their descent from a common progenitor, together with their
subsequent adaptation to diversified conditions. On any other view, the
similarity of pattern between the hand of a man or monkey, the foot of a
horse, the flipper of a seal, the wing of a bat, etc., is utterly
inexplicable. (56. Prof. Bianconi, in a recently published work,
illustrated by admirable engravings (‘La Theorie Darwinienne et la creation
dite independante,’ 1874), endeavours to shew that homological structures,
in the above and other cases, can be fully explained on mechanical
principles, in accordance with their uses. No one has shewn so well, how
admirably such structures are adapted for their final purpose; and this
adaptation can, as I believe, be explained through natural selection. In
considering the wing of a bat, he brings forward (p. 218) what appears to
me (to use Auguste Comte’s words) a mere metaphysical principle, namely,
the preservation “in its integrity of the mammalian nature of the animal.”
In only a few cases does he discuss rudiments, and then only those parts
which are partially rudimentary, such as the little hoofs of the pig and
ox, which do not touch the ground; these he shews clearly to be of service
to the animal. It is unfortunate that he did not consider such cases as
the minute teeth, which never cut through the jaw in the ox, or the mammae
of male quadrupeds, or the wings of certain beetles, existing under the
soldered wing-covers, or the vestiges of the pistil and stamens in various
flowers, and many other such cases. Although I greatly admire Prof.
Bianconi’s work, yet the belief now held by most naturalists seems to me
left unshaken, that homological structures are inexplicable on the
principle of mere adaptation.) It is no scientific explanation to assert
that they have all been formed on the same ideal plan. With respect to
development, we can clearly understand, on the principle of variations
supervening at a rather late embryonic period, and being inherited at a
corresponding period, how it is that the embryos of wonderfully different
forms should still retain, more or less perfectly, the structure of their
common progenitor. No other explanation has ever been given of the
marvellous fact that the embryos of a man, dog, seal, bat, reptile, etc.,
can at first hardly be distinguished from each other. In order to
understand the existence of rudimentary organs, we have only to suppose
that a former progenitor possessed the parts in question in a perfect
state, and that under changed habits of life they became greatly reduced,
either from simple disuse, or through the natural selection of those
individuals which were least encumbered with a superfluous part, aided by
the other means previously indicated.

Thus we can understand how it has come to pass that man and all other
vertebrate animals have been constructed on the same general model, why
they pass through the same early stages of development, and why they retain
certain rudiments in common. Consequently we ought frankly to admit their
community of descent: to take any other view, is to admit that our own
structure, and that of all the animals around us, is a mere snare laid to
entrap our judgment. This conclusion is greatly strengthened, if we look
to the members of the whole animal series, and consider the evidence
derived from their affinities or classification, their geographical
distribution and geological succession. It is only our natural prejudice,
and that arrogance which made our forefathers declare that they were
descended from demi-gods, which leads us to demur to this conclusion. But
the time will before long come, when it will be thought wonderful that
naturalists, who were well acquainted with the comparative structure and
development of man, and other mammals, should have believed that each was
the work of a separate act of creation.

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