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Library: Historical Documents: Charles Darwin: Descent of Man: Chapter 1


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Descent of Man [ 1871]

Charles Darwin [ 1809 - 1882 ]

 

Part One: Descent or Origin of Man

Chapter I - The Evidence of the Descent of Man from some Lower Form




  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,

&c.? Is man subject to similar malconformations, the result of

arrested development, of reduplication of parts, &c., 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 shows 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,* 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) remarks: "Les

differences reelles qui existent entre l'encephale de l'homme et celui

des singes superieurs, sont bien minimes. It 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.



  * 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.

  *(2) Lec. sur la Phys., 1866, p. 890, as quoted by M. Dally, L'Ordre

des Primates et le Transformisme, 1868, p. 29.



  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, variola, the

glanders, syphilis, cholera, herpes, &c.;* and this fact proves the

close similarity*(2) 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,*(3) 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 spirituous liquors: they will

also, as I have myself seen, smoke tobacco with pleasure.*(4) 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.*(5) 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.



  * 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.

  *(2) A reviewer has criticised (British Quarterly Review, Oct. 1,

1871, p. 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.

  *(3) Naturgeschichte der Saugethiere von Paraguay, 1830, s. 50.

  *(4) The same tests are common to some animals much lower in the

scale. Mr. A. Nicols 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.

  *(5) Brehm, Illustriertes Thierleben, B. i., 1864, 75, 86. On the

Ateles, s. 105. For other analogous statements, see ss. 25, 107.



  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.* Man is subject, like

other mammals, birds, and even insects,*(2) 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.*(3)



  * Dr. W. Lauder Lindsay, Edinburgh Veterinary Review, July, 1858, p.

13.

  *(2) 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., p. 305,

has seen a dog suffering from tertian ague. Hereafter I shall return

to this subject.

  *(3) I have given the evidence on this head in my Variation of

Animals and Plants under Domestication, vol. ii., p. 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,* 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.*(2) 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.*(3) Man differs from woman in size,

bodily strength, hairiness, &c., 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.



  * 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 ministirs

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.

  *(2) 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.

  *(3) Huxley, Man's Place in Nature, 1863, p. 34.



  Embryonic Development. 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,* "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."



  * Man's Place in Nature, 1863, p. 67.



  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.*



  * The human embryo (see upper fig.) is from Ecker, Icones Phys.,

1851-1859, tab. xxx., fig. 2. The drawing of this embryo is much

magnified. The embryo of the dog is from Bischoff,

Entwicklungsgeschichte des Hunde-Eies, 1845, tab. xi., fig. 42 B. This

drawing is 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 extending considerably beyond

the rudimentary legs."* In the embryos of all air-breathing

vertebrates, certain glands, called the corpora Wolffiana,

correspond with, and act like the kidneys of mature fishes.*(2) 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."*(3) The great toe, as Professor Owen remarks,*(4)

"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*(5) 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,*(6) 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."



  * Prof. Wyman in Proceedings of the American Academy of Sciences,

vol. iv., 1860, p. 17.

  *(2) Owen, Anatomy of Vertebrates, vol. i., p. 533.

  *(3) Die Grosshirnwindungen des Menschen 1868, s. 95.

  *(4) Anatomy of Vertebrates, vol. ii., p. 553.

  *(5) Proc. Soc. Nat. Hist., Boston, 1863, vol. ix., p. 185.

  *(6) Man's Place in Nature, p. 65.



  Rudiments. This subject, though not intrinsically more important

than the two last, will for several reasons be treated here more

fully.* 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 mammee 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.



  * 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

Shopfungsgeschichte.



  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,* are

difficult to understand. The final and complete suppression of a part,

already useless and much reduced in size, in which case neither

compensation or 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,*(2) I need here say no more on this head.



  * Some good criticisms on this subject have been given by Messrs.

Murie and Mivart, in Transactions, Zoological Society, 1869, vol.

vii., p. 92.

  *(2) Variation of Animals and Plants under Domestication, vol. ii

pp. 317 and 397. See also Origin of Species.(OOS)



  Rudiments of various muscles have been observed in many parts of the

human body;* 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, &c., all of which must be referred to the system of

the panniculus. He has also shewn*(2) 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 upward 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."



  * For instance, M. Richard (Annales des Sciences Nat., 3d 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.

  *(2) Prof. W. Turner, Proceedings of the Royal Society of Edinburgh,

1866-67, p. 65.



  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.*



  * 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;*

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, &c.)

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,*(2) 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.*(3) 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 can not say. It may be, though I am not

satified 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 inhabiting 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";*(4) and, as I hear from Prof.

Preyer, it is not rarely absent in the negro.



  * Canestrini quotes Hyrtl. (Annuario della Soc. dei Naturalisti,

Modena, 1897, p. 97) to the same effect.

  *(2) 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.

  *(3) Prof. A. Macalister, Annals and Magazine of Natural History,

vol. vii., 1871, p. 342.

  *(4) Mr. St. George Mivart, Elementary Anatomy, 1873, p. 396.



  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 (see 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,* 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,*(2) 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 microcephalus 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*(3) 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. The

following woodcut (see fig. 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 chang 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.



  * 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.

  *(2) Uber das Darwin'sche Spitzohr," Archiv fur Path. Anst. und

Phys., 1871, p. 485.

  *(3) The Expression of the Emotions, p. 136.



  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 eyeball. 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.*



  * 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.* 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,*(2) that the sense of smell in man "is singularly

effective in recalling vividly the ideas and images of forgotten

scenes and places."



  * 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, &c., 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.

  *(2) The Physiology and Pathology of Mind, 2nd ed., 1868, p. 134.



  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 a 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.* 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.*(2)



  * 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.

  *(2) 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 Maeacus, 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* 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.*(2) 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.



  * Eschricht, ibid., ss. 40, 47.

  *(2) 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.



  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.* 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.*(2) 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,*(3)

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.*(4)



  * Dr. Webb, "Teeth in Man and the Anthropoid Apes," as quoted by Dr.

C. Carter Blake in Anthropological Review, July, 1867, p. 299.

  *(2) Owen, Anatomy of Vertebrates, vol. iii., pp. 320, 321, and 325.

  *(3) "On the Primitive Form of the Skull," Eng. translat., in

Anthropological Review, Oct., 1868, p. 426.

  *(4) 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.* 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*(2) 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.*(3)



  * Owen, Anatomy of Vertebrates, vol. iii., pp 416, 434, 441.

  *(2) Annuario della Soc. d. Nat. Modena, 1867, p. 94.

  *(3) 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,* 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.



  * 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.



  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,* 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*(2) 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.



  * Mr. St. George Mivart, Transactions Phil. Soc., 1867, p. 310.

  *(2) "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.



  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 (see fig. 1) of a human embryo. Even after

birth it has been known, in certain rare and anomalous cases,* 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.*(2) 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.



  * 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 Niederland. Archiv fur

Zoologie, December, 1871).

  *(2) Owen, On the Nature of Limbs, 1849, p. 114.



  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 (Maeacus), 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.* Some other rudimentary structures

belonging to the reproductive system might have been here adduced.*(2)



  * 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.

  *(2) 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, &c., is utterly inexplicable.* 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 variation 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, &c., 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.



  * Prof. Bianconi, in a recently published work, illustrated by

admirable engravings (La Theorie Darwinienne et la creation dite

independante, 1874), endeavours to show 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 shows 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.



  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 demigods,

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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