Produced by Amy E. Zelmer
ON THE RELATIONS OF MAN TO THE LOWER ANIMALS
By Thomas H. Huxley
Multis videri poterit, majorem esso differentiam Simiae et
Hominis, quam diei et noctis; verum tamen hi, comparatione
instituta inter summos Europae Heroes et Hottentottos ad
Caput bonae spei degentes, difficillime sibi persuadebunt,
has eosdem habere natales; vel si virginem nobilem aulicam,
maxime comtam et humanissimam, conferre vellent cum homine
sylvestri et sibi relicto, vix augurari possent, hunc et
illam ejusdem esse speciei.--'Linnaei Amoenitates Acad.
"Anthropomorpha."'
THE question of questions for mankind--the problem which underlies
all others, and is more deeply interesting than any other--is the
ascertainment of the place which Man occupies in nature and of his
relations to the universe of things. Whence our race has come; what are
the limits of our power over nature, and of nature's power over us; to
what goal we are tending; are the problems which present themselves anew
and with undiminished interest to every man born into the world. Most of
us, shrinking from the difficulties and dangers which beset the seeker
after original answers to these riddles, are contented to ignore them
altogether, or to smother the investigating spirit under the featherbed
of respected and respectable tradition. But, in every age, one or two
restless spirits, blessed with that constructive genius, which can
only build on a secure foundation, or cursed with the spirit of mere
scepticism, are unable to follow in the well-worn and comfortable track
of their forefathers and contemporaries, and unmindful of thorns and
stumbling-blocks, strike out into paths of their own. The sceptics end
in the infidelity which asserts the problem to be insoluble, or in
the atheism which denies the existence of any orderly progress and
governance of things: the men of genius propound solutions which grow
into systems of Theology or of Philosophy, or veiled in musical language
which suggests more than it asserts, take the shape of the Poetry of an
epoch.
Each such answer to the great question, invariably asserted by the
followers of its propounder, if not by himself, to be complete and
final, remains in high authority and esteem, it may be for one century,
or it may be for twenty: but, as invariably, Time proves each reply
to have been a mere approximation to the truth--tolerable chiefly on
account of the ignorance of those by whom it was accepted, and wholly
intolerable when tested by the larger knowledge of their successors.
In a well-worn metaphor, a parallel is drawn between the life of man
and the metamorphosis of the caterpillar into the butterfly; but the
comparison may be more just as well as more novel, if for its former
term we take the mental progress of the race. History shows that the
human mind, fed by constant accessions of knowledge, periodically grows
too large for its theoretical coverings, and bursts them asunder
to appear in new habiliments, as the feeding and growing grub, at
intervals, casts its too narrow skin and assumes another, itself but
temporary. Truly the imago state of Man seems to be terribly distant,
but every moult is a step gained, and of such there have been many.
Since the revival of learning, whereby the Western races of Europe were
enabled to enter upon that progress towards true knowledge, which was
commenced by the philosophers of Greece, but was almost arrested in
subsequent long ages of intellectual stagnation, or, at most, gyration,
the human larva has been feeding vigorously, and moulting in proportion.
A skin of some dimension was cast in the 16th century, and another
towards the end of the 18th, while, within the last fifty years, the
extraordinary growth of every department of physical science has spread
among us mental food of so nutritious and stimulating a character that
a new ecdysis seems imminent. But this is a process not unusually
accompanied by many throes and some sickness and debility, or, it may
be, by graver disturbances; so that every good citizen must feel bound
to facilitate the process, and even if he have nothing but a scalpel to
work withal, to ease the cracking integument to the best of his ability.
In this duty lies my excuse for the publication of these essays. For it
will be admitted that some knowledge of man's position in the animate
world is an indispensable preliminary to the proper understanding of his
relations to the universe--and this again resolves itself, in the long
run, into an inquiry into the nature and the closeness of the ties which
connect him with those singular creatures whose history [1] has been
sketched in the preceding pages.
The importance of such an inquiry is indeed intuitively manifest Brought
face to face with these blurred copies of himself, the least thoughtful
of men is conscious of a certain shock, due perhaps, not so much to
disgust at the aspect of what looks like an insulting caricature, as
to the awakening of a sudden and profound mistrust of time-honoured
theories and strongly-rooted prejudices regarding his own position in
nature, and his relations to the under-world of life; while that which
remains a dim suspicion for the unthinking, becomes a vast argument,
fraught with the deepest consequences, for all who are acquainted with
the recent progress of the anatomical and physiological sciences.
I now propose briefly to unfold that argument, and to set forth, in
a form intelligible to those who possess no special acquaintance
with anatomical science, the chief facts upon which all conclusions
respecting the nature and the extent of the bonds which connect man with
the brute world must be based: I shall then indicate the one immediate
conclusion which, in my judgment, is justified by those facts, and I
shall finally discuss the bearing of that conclusion upon the hypotheses
which have been entertained respecting the Origin of Man.
The facts to which I would first direct the reader's attention, though
ignored by many of the professed instructors of the public mind, are
easy of demonstration and are universally agreed to by men of science;
while their significance is so great, that whoso has duly pondered over
them will, I think, find little to startle him in the other revelations
of Biology. I refer to those facts which have been made known by the
study of Development.
It is a truth of very wide, if not of universal, application, that every
living creature commences its existence under a form different from, and
simpler than, that which it eventually attains.
[Illustration: FIG. 12.--A. Egg of the Dog, with the vitelline membrane
burst, so as to give exit to the yelk, the germinal vesicle (a), and
its included spot (b). B. C. D. E F. Successive changes of the yelk
indicated in the text. After Bischoff.]
The oak is a more complex thing than the little rudimentary plant
contained in the acorn; the caterpillar is more complex than the egg;
the butterfly than the caterpillar; and each of these beings, in passing
from its rudimentary to its perfect condition, runs through a series
of changes, the sum of which is called its Development. In the higher
animals these changes are extremely complicated; but, within the last
half century, the labours of such men as Von Baer, Rathke, Reichert,
Bischof, and Remak, have almost completely unravelled them, so that
the successive stages of development which are exhibited by a Dog, for
example, are now as well known to the embryologist as are the steps of
the metamorphosis of the silkworm moth to the school-boy. It will be
useful to consider with attention the nature and the order of the
stages of canine development, as an example of the process in the higher
animals generally.
The Dog, like all animals, save the very lowest (and further inquiries
may not improbably remove the apparent exception), commences its
existence as an egg: as a body which is, in every sense, as much an egg
as that of a hen, but is devoid of that accumulation of nutritive matter
which confers upon the bird's egg its exceptional size and domestic
utility; and wants the shell, which would not only be useless to an
animal incubated within the body of its parent, but would cut it off
from access to the source of that nutriment which the young creature
requires, but which the minute egg of the mammal does not contain within
itself.
The Dog's egg is, in fact, a little spheroidal bag (Fig. 12), formed
of a delicate transparent membrane called the 'vitelline membrane', and
about 1/130 to 1/120th of an inch in diameter. It contains a mass of
viscid nutritive matter--the 'yelk'--within which is inclosed a second
much more delicate spheroidal bag, called the 'germinal vesicle' (a). In
this, lastly, lies a more solid rounded body, termed the 'germinal spot'
(b).
The egg, or 'Ovum,' is originally formed within a gland, from which,
in due season, it becomes detached, and passes into the living chamber
fitted for its protection and maintenance during the protracted process
of gestation. Here, when subjected to the required conditions, this
minute and apparently insignificant particle of living matter becomes
animated by a new and mysterious activity. The germinal vesicle and
spot cease to be discernible (their precise fate being one of the yet
unsolved problems of embryology), but the yelk becomes circumferentially
indented, as if an invisible knife had been drawn round it, and thus
appears divided into two hemispheres (Fig. 12, C).
By the repetition of this process in various planes, these hemispheres
become subdivided, so that four segments are produced (D); and these,
in like manner, divide and subdivide again, until the whole yelk is
converted into a mass of granules, each of which consists of a minute
spheroid of yelk-substance, inclosing a central particle, the so-called
'nucleus' (F). Nature, by this process, has attained much the same
result as that at which a human artificer arrives by his operations in a
brickfield. She takes the rough plastic material of the yelk and breaks
it up into well-shaped tolerably even-sized masses, handy for building
up into any part of the living edifice.
[Illustration: FIG. 13.--Earliest rudiment of the Dog. B. Rudiment
further advanced, showing the foundations of the head, tail, and
vertebral column. C. The very young puppy, with attached ends of the
yelk-sac and allantois, and invested in the amnion.]
Next, the mass of organic bricks, or 'cells' as they are technically
called, thus formed, acquires an orderly arrangement, becoming converted
into a hollow spheroid with double walls. Then, upon one side of this
spheroid, appears a thickening, and, by and bye, in the centre of the
area of thickening, a straight shallow groove (Fig. 13, A) marks the
central line of the edifice which is to be raised, or, in other words,
indicates the position of the middle line of the body of the future
dog. The substance bounding the groove on each side next rises up into
a fold, the rudiment of the side wall of that long cavity, which will
eventually lodge the spinal marrow and the brain; and in the floor of
this chamber appears a solid cellular cord, the so-called 'notochord.'
One end of the inclosed cavity dilates to form the head (Fig. 13, B),
the other remains narrow, and eventually becomes the tail; the side
walls of the body are fashioned out of the downward continuation of the
walls of the groove; and from them, by and bye, grow out little buds
which, by degrees, assume the shape of limbs. Watching the fashioning
process stage by stage, one is forcibly reminded of the modeller in
clay. Every part, every organ, is at first, as it were, pinched up
rudely, and sketched out in the rough; then shaped more accurately; and
only, at last, receives the touches which stamp its final character.
Thus, at length, the young puppy assumes such a form as is shown in
Fig. 13, C. In this condition it has a disproportionately large head, as
dissimilar to that of a dog as the bud-like limbs are unlike his legs.
The remains of the yelk, which have not yet been applied to the
nutrition and growth of the young animal, are contained in a sac
attached to the rudimentary intestine, and termed the yelk sac,
or 'umbilical vesicle.' Two membranous bags, intended to subserve
respectively the protection and nutrition of the young creature, have
been developed from the skin and from the under and hinder surface
of the body; the former, the so-called 'amnion,' is a sac filled with
fluid, which invests the whole body of the embryo, and plays the part
of a sort of water-bed for it; the other, termed the 'allantois,' grows
out, loaded with blood-vessels, from the ventral region, and eventually
applying itself to the walls of the cavity, in which the developing
organism is contained, enables these vessels to become the channel
by which the stream of nutriment, required to supply the wants of the
offspring, is furnished to it by the parent.
The structure which is developed by the interlacement of the vessels of
the offspring with those of the parent, and by means of which the former
is enabled to receive nourishment and to get rid of effete matters, is
termed the 'Placenta.'
It would be tedious, and it is unnecessary for my present purpose, to
trace the process of development further; suffice it to say, that, by
a long and gradual series of changes, the rudiment here depicted and
described becomes a puppy, is born, and then, by still slower and less
perceptible steps, passes into the adult Dog.
There is not much apparent resemblance between a barndoor Fowl and the
Dog who protects the farm-yard. Nevertheless the student of development
finds, not only that the chick commences its existence as an egg,
primarily identical, in all essential respects, with that of the Dog,
but that the yelk of this egg undergoes division--that the primitive
groove arises, and that the contiguous parts of the germ are fashioned,
by precisely similar methods, into a young chick, which, at one stage
of its existence, is so like the nascent Dog, that ordinary inspection
would hardly distinguish the two.
The history of the development of any other vertebrate animal, Lizard,
Snake, Frog, or Fish, tells the same story. There is always, to
begin with, an egg having the same essential structure as that of the
Dog:--the yelk of that egg always undergoes division, or 'segmentation'
as it is often called: the ultimate products of that segmentation
constitute the building materials for the body of the young animal;
and this is built up round a primitive groove, in the floor of which
a notochord is developed. Furthermore, there is a period in which the
young of all these animals resemble one another, not merely in
outward form, but in all essentials of structure, so closely, that the
differences between them are inconsiderable, while, in their subsequent
course, they diverge more and more widely from one another. And it is a
general law, that, the more closely any animals resemble one another
in adult structure, the longer and the more intimately do their embryos
resemble one another: so that, for example, the embryos of a Snake and
of a Lizard remain like one another longer than do those of a Snake and
of a Bird; and the embryo of a Dog and of a Cat remain like one another
for a far longer period than do those of a Dog and a Bird; or of a Dog
and an Opossum; or even than those of a Dog and a Monkey.
Thus the study of development affords a clear test of closeness of
structural affinity, and one turns with impatience to inquire what
results are yielded by the study of the development of Man. Is he
something apart? Does he originate in a totally different way from Dog,
Bird, Frog, and Fish, thus justifying those who assert him to have no
place in nature and no real affinity with the lower world of animal
life? Or does he originate in a similar germ, pass through the same
slow and gradually progressive modifications,--depend on the same
contrivances for protection and nutrition, and finally enter the world
by the help of the same mechanism? The reply is not doubtful for a
moment, and has not been doubtful any time these thirty years. 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 the Apes,
than the Apes are to the Dog.
The Human ovum is about 1/125 of an inch in diameter, and might be
described in the same terms as that of the Dog, so that I need only
refer to the figure illustrative (14 A) of its structure. It leaves the
organ in which it is formed in a similar fashion and enters the organic
chamber prepared for its reception in the same way, the conditions of
its development being in all respects the same. It has not yet been
possible (and only by some rare chance can it ever be possible) to
study the human ovum in so early a developmental stage as that of yelk
division, but there is every reason to conclude that the changes
it undergoes are identical with those exhibited by the ova of
other vertebrated animals; for the formative materials of which the
rudimentary human body is composed, in the earliest conditions in which
it has been observed, are the same as those of other animals. Some of
these earliest stages are figured below, and, as will be seen, they are
strictly comparable to the very early states of the Dog; the marvellous
correspondence between the two which is kept up, even for some time, as
development advances, becoming apparent by the simple comparison of the
figures with those on page 249.
[Illustration: Fig. 14.--A. Human ovum (after Kolliker). a. germinal
vesicle. b. germinal spot. B. A very early condition of Man, with
yelk-sac, allantois, and amnion (original). C. A more advanced stage
(after Kolliker), compare Fig. 13, C.]
Indeed, it is very long before the body of the young human being can be
readily discriminated from that of the young puppy; but, at a tolerably
early period, the two become distinguishable by the different form of
their adjuncts, the yelk-sac and the allantois. The former, in the Dog,
becomes long and spindle-shaped, while in Man it remains spherical; the
latter, in the Dog, attains an extremely large size, and the vascular
processes which are developed from it and eventually give rise to the
formation of the placenta (taking root, as it were, in the parental
organism, so as to draw nourishment therefrom, as the root of a tree
extracts it from the soil) are arranged in an encircling zone, while
in Man, the allantois remains comparatively small, and its vascular
rootlets are eventually restricted to one disk-like spot. Hence, while
the placenta of the Dog is like a girdle, that of Man has the cake-like
form, indicated by the name of the organ.
But, exactly in those respects in which the developing Man differs
from the Dog, he resembles the ape, which, like man, has a spheroidal
yelk-sac and a discoidal--sometimes partially lobed--placenta. So that
it is only 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 development, as the man does.
Startling as the last assertion may appear to be, it is demonstrably
true, and it alone appears to me sufficient to place beyond all doubt
the structural unity of man with the rest of the animal world, and more
particularly and closely with the apes.
Thus, identical in the physical processes by which he
originates--identical in the early stages of his formation--identical in
the mode of his nutrition before and after birth, with the animals which
lie immediately below him in the scale--Man, if his adult and perfect
structure be compared with theirs, exhibits, as might be expected, a
marvellous likeness of organization. He resembles them as they resemble
one another--he differs from them as they differ from one another.--And,
though these differences and resemblances cannot be weighed and
measured, their value may be readily estimated; the scale or standard
of judgment, touching that value, being afforded and expressed by the
system of classification of animals now current among zoologists.
A careful study of the resemblances and differences presented by
animals has, in fact, led naturalists to arrange them into groups, or
assemblages, all the members of each group presenting a certain amount
of definable resemblance, and the number of points of similarity being
smaller as the group is larger and 'vice versa'. Thus, all creatures
which agree only in presenting the few distinctive marks of animality
form the 'Kingdom' ANIMALIA. The numerous animals which agree only in
possessing the special characters of Vertebrates form one 'Sub-Kingdom'
of this Kingdom. Then the Sub-kingdom VERTEBRATA is subdivided into the
five 'Classes,' Fishes, Amphibians, Reptiles, Birds, and Mammals, and
these into smaller groups called 'Orders'; these into 'Families'
and 'Genera'; while the last are finally broken up into the smallest
assemblages, which are distinguished by the possession of constant,
not-sexual, characters. These ultimate groups are Species.
Every year tends to bring about a greater uniformity of opinion
throughout the zoological world as to the limits and characters of these
groups, great and small. At present, for example, no one has the
least doubt regarding the characters of the classes Mammalia, Aves, or
Reptilia; nor does the question arise whether any thoroughly well-known
animal should be placed in one class or the other. Again, there is
a very general agreement respecting the characters and limits of
the orders of Mammals, and as to the animals which are structurally
necessitated to take a place in one or another order.
No one doubts, for example, that the Sloth and the Ant-eater, the
Kangaroo and the Opossum, the Tiger and the Badger, the Tapir and
the Rhinoceros, are respectively members of the same orders. These
successive pairs of animals may, and some do, differ from one another
immensely, in such matters as the proportions and structure of their
limbs; the number of their dorsal and lumbar vertebrae; the adaptation
of their frames to climbing, leaping, or running; the number and form
of their teeth; and the characters of their skulls and of the contained
brain. But, with all these differences, they are so closely connected in
all the more important and fundamental characters of their organization,
and so distinctly separated by these same characters from other animals,
that zoologists find it necessary to group them together as members
of one order. And if any new animal were discovered, and were found to
present no greater difference from the Kangaroo and the Opossum, for
example, than these animals do from one another, the zoologist would not
only be logically compelled to rank it in the same order with these, but
he would not think of doing otherwise.
Bearing this obvious course of zoological reasoning in mind, let us
endeavour for a moment to disconnect our thinking selves from the mask
of humanity; let us imagine ourselves scientific Saturnians, if you
will, fairly acquainted with such animals as now inhabit the Earth, and
employed in discussing the relations they bear to a new and singular
'erect and featherless biped,' which some enterprising traveller,
overcoming the difficulties of space and gravitation, has brought from
that distant planet for our inspection, well preserved, may be, in a
cask of rum. We should all, at once, agree upon placing him among the
mammalian vertebrates; and his lower jaw, his molars, and his brain,
would leave no room for doubting the systematic position of the new
genus among those mammals, whose young are nourished during gestation by
means of a placenta, or what are called the 'placental mammals.'
Further, the most superficial study would at once convince us that,
among the orders of placental mammals, neither the Whales, nor the
hoofed creatures, nor the Sloths and Ant-eaters, nor the carnivorous
Cats, Dogs, and Bears, still less the Rodent Rats and Rabbits, or the
Insectivorous Moles and Hedgehogs, or the Bats, could claim our 'Homo',
as one of themselves.
There would remain then, but one order for comparison, that of the Apes
(using that word in its broadest sense), and the question for discussion
would narrow itself to this--is Man so different from any of these Apes
that he must form an order by himself? Or does he differ less from them
than they differ from one another, and hence must take his place in the
same order with them?
Being happily free from all real, or imaginary, personal interest in the
results of the inquiry thus set afoot, we should proceed to weigh the
arguments on one side and on the other, with as much judicial calmness
as if the question related to a new Opossum. We should endeavour to
ascertain, without seeking either to magnify or diminish them, all the
characters by which our new Mammal differed from the Apes; and if
we found that these were of less structural value, than those which
distinguish certain members of the Ape order from others universally
admitted to be of the same order, we should undoubtedly place the newly
discovered tellurian genus with them.
I now proceed to detail the facts which seem to me to leave us no choice
but to adopt the last mentioned course.
It is quite certain that the Ape which most nearly approaches man,
in the totality of its organization, is either the Chimpanzee or the
Gorilla; and as it makes no practical difference, for the purposes of
my present argument, which is selected for comparison, on the one hand,
with Man, and on the other hand, with the rest of the Primates, [2]
I shall select the latter (so far as its organization is known)--as a
brute now so celebrated in prose and verse, that all must have heard of
him, and have formed some conception of his appearance. I shall take up
as many of the most important points of difference between man and
this remarkable creature, as the space at my disposal will allow me to
discuss, and the necessities of the argument demand; and I shall inquire
into the value and magnitude of these differences, when placed side by
side with those which separate the Gorilla from other animals of the
same order.
In the general proportions of the body and limbs there is a remarkable
difference between the Gorilla and Man, which at once strikes the eye.
The Gorilla's brain-case is smaller, its trunk larger, its lower limbs
shorter, its upper limbs longer in proportion than those of Man.
I find that the vertebral column of a full-grown Gorilla, in the Museum
of the Royal College of Surgeons, measures 27 inches along its anterior
curvature, from the upper edge of the atlas, or first vertebra of the
neck, to the lower extremity of the sacrum; that the arm, without the
hand, is 31-1/2 inches long; that the leg, without the foot, is 26-1/2
inches long; that the hand is 9-3/4 inches long; the foot 11-1/4 inches
long.
In other words, taking the length of the spinal column as 100, the arm
equals 115, the leg 96, the hand 36, and the foot 41.
In the skeleton of a male Bosjesman, in the same collection, the
proportions, by the same measurement, to the spinal column, taken as
100, are--the arm 78, the leg 110, the hand 26, and the foot 32. In a
woman of the same race the arm is 83, and the leg 120, the hand and foot
remaining the same. In a European skeleton I find the arm to be 80, the
leg 117, the hand 26, the foot 35.
Thus the leg is not so different as it looks at first sight, in its
proportion to the spine in the Gorilla and in the Man--being very
slightly shorter than the spine in the former, and between 1/10 and 1/5
longer than the spine in the latter. The foot is longer and the hand
much longer in the Gorilla; but the great difference is caused by the
arms, which are very much longer than the spine in the Gorilla, very
much shorter than the spine in the Man.
The question now arises how are the other Apes related to the Gorilla
in these respects--taking the length of the spine, measured in the same
way, at 100. In an adult Chimpanzee, the arm is only 96, the leg 90, the
hand 43, the foot 39--so that the hand and the leg depart more from the
human proportion and the arm less, while the foot is about the same as
in the Gorilla.
In the Orang, the arms are very much longer than in the Gorilla (122),
while the legs are shorter (88); the foot is longer than the hand (52
and 48), and both are much longer in proportion to the spine.
In the other man-like Apes again, the Gibbons, these proportions are
still further altered; the length of the arms being to that of the
spinal column as 19 to 11; while the legs are also a third longer than
the spinal column, so as to be longer than in Man, instead of shorter.
The hand is half as long as the spinal column, and the foot, shorter
than the hand, is about 5/11ths of the length of the spinal column.
Thus 'Hylobates' is as much longer in the arms than the Gorilla, as the
Gorilla is longer in the arms than Man; while, on the other hand, it
is as much longer in the legs than the Man, as the Man is longer in the
legs than the Gorilla, so that it contains within itself the extremest
deviations from the average length of both pairs of limbs (See the
illustration on page 196).
The Mandrill presents a middle condition, the arms and legs being nearly
equal in length, and both being shorter than the spinal column; while
hand and foot have nearly the same proportions to one another and to the
spine, as in Man.
In the Spider monkey ('Ateles') the leg is longer than the spine, and
the arm than the leg; and, finally, in that remarkable Lemurine form,
the Indri ('Lichanotus'), the leg is about as long as the spinal column,
while the arm is not more than 11/18 of its length; the hand having
rather less and the foot rather more, than one-third the length of the
spinal column.
These examples might be greatly multiplied, but they suffice to show
that, in whatever proportion of its limbs the Gorilla differs from
Man, the other Apes depart still more widely from the Gorilla and that,
consequently, such differences of proportion can have no ordinal value.
We may next consider the differences presented by the trunk, consisting
of the vertebral column, or backbone, and the ribs and pelvis, or
bony hip-basin, which are connected with it, in Man and in the Gorilla
respectively.
In Man, in consequence partly of the disposition of the articular
surfaces of the vertebrae, and largely of the elastic tension of some of
the fibrous bands, or ligaments, which connect these vertebrae together,
the spinal column, as a whole, has an elegant S-like curvature, being
convex forwards in the neck, concave in the back, convex in the loins,
or lumbar region, and concave again in the sacral region; an arrangement
which gives much elasticity to the whole backbone, and diminishes the
jar communicated to the spine, and through it to the head, by locomotion
in the erect position.
Furthermore, under ordinary circumstances, Man has seven vertebrae in
his neck, which are called 'cervical'; twelve succeed these, bearing
ribs and forming the upper part of the back, whence they are termed
'dorsal'; five lie in the loins, bearing no distinct, or free, ribs, and
are called 'lumbar'; five, united together into a great bone, excavated
in front, solidly wedged in between the hip bones, to form the back of
the pelvis, and known by the name of the 'sacrum', succeed these; and
finally, three or four little more or less movable bones, so small as to
be insignificant, constitute the 'coccyx' or rudimentary tail.
In the Gorilla, the vertebral column is similarly divided into cervical,
dorsal, lumbar, sacral, and coccygeal vertebrae, and the total number
of cervical and dorsal vertebrae, taken together, is the same as in
Man; but the development of a pair of ribs to the first lumbar vertebra,
which is an exceptional occurrence in Man, is the rule in the Gorilla;
and hence, as lumbar are distinguished from dorsal vertebrae only by the
presence or absence of free ribs, the seventeen "dorso-lumbar" vertebrae
of the Gorilla are divided into thirteen dorsal and four lumbar, while
in Man they are twelve dorsal and five lumbar.
[Illustration: FIG. 15.--Front and side views of the bony pelvis of Man,
the Gorilla and Gibbon: reduced from drawings made from nature, of the
same absolute length, by Mr. Waterhouse Hawkins.]
Not only, however, does Man occasionally possess thirteen pair of
ribs, but the Gorilla sometimes has fourteen pairs, while an Orang-Utan
skeleton in the Museum of the Royal College of Surgeons has twelve
dorsal and five lumbar vertebrae, as in Man. Cuvier notes the same
number in a 'Hylobates'. On the other hand, among the lower Apes, many
possess twelve dorsal and six or seven lumbar vertebrae; the
Douroucouli has fourteen dorsal and eight lumbar, and a Lemur ('Stenops
tardigradus') has fifteen dorsal and nine lumbar vertebrae.
The vertebral column of the Gorilla, as a whole, differs from that
of Man in the less marked character of its curves, especially in the
slighter convexity of the lumbar region. Nevertheless, the curves are
present, and are quite obvious in young skeletons of the Gorilla and
Chimpanzee which have been prepared without removal of the ligaments. In
young Orangs similarly preserved, on the other hand, the spinal column
is either straight, or even concave forwards, throughout the lumbar
region.
Whether we take these characters then, or such minor ones as those which
are derivable from the proportional length of the spines of the cervical
vertebrae, and the like, there is no doubt whatsoever as to the marked
difference between Man and the Gorilla; but there is as little, that
equally marked differences, of the very same order, obtain between the
Gorilla and the lower Apes.
The Pelvis, or bony girdle of the hips, of Man is a strikingly human
part of his organization; the expanded haunch bones affording support
for his viscera during his habitually erect posture, and giving space
for the attachment of the great muscles which enable him to assume and
to preserve that attitude. In these respects the pelvis of the Gorilla
differs very considerably from his (Fig. 15). But go no lower than the
Gibbon, and see how vastly more he differs from the Gorilla than the
latter does from Man, even in this structure. Look at the flat, narrow
haunch bones--the long and narrow passage--the coarse, outwardly curved,
ischiatic prominences on which the Gibbon habitually rests, and which
are coated by the so-called "callosities," dense patches of skin, wholly
absent in the Gorilla, in the Chimpanzee, and in the Orang, as in Man!
In the lower Monkeys and in the Lemurs the difference becomes more
striking still, the pelvis acquiring an altogether quadrupedal
character.
But now let us turn to a nobler and more characteristic organ--that
by which the human frame seems to be, and indeed is, so strongly
distinguished from all others,--I mean the skull. The differences
between a Gorilla's skull and a Man's are truly immense (Fig. 16).
In the former, the face, formed largely by the massive jaw-bones,
predominates over the brain case, or cranium proper: in the latter, the
proportions of the two are reversed. In the Man, the occipital foramen,
through which passes the great nervous cord connecting the brain with
the nerves of the body, is placed just behind the centre of the base of
the skull, which thus becomes evenly balanced in the erect posture; in
the Gorilla, it lies in the posterior third of that base. In the Man,
the surface of the skull is comparatively smooth, and the supraciliary
ridges or brow prominences usually project but little--while, in the
Gorilla, vast crests are developed upon the skull, and the brow ridges
overhang, the cavernous orbits, like great penthouses.
Sections of the skulls, however, show that some of the apparent defects
of the Gorilla's cranium arise, in fact, not so much from deficiency of
brain case as from excessive development of the parts of the face.
The cranial cavity is not ill-shaped, and the forehead is not truly
flattened or very retreating, its really well-formed curve being simply
disguised by the mass of bone which is built up against it (Fig. 16).
But the roofs of the orbits rise more obliquely into the cranial cavity,
thus diminishing the space for the lower part of the anterior lobes of
the brain, and the absolute capacity of the cranium is far less than
that of Man. So far as I am aware, no human cranium belonging to an
adult man has yet been observed with a less cubical capacity than
62 cubic inches, the smallest cranium observed in any race of men by
Morton, measuring 63 cubic inches; while, on the other hand, the most
capacious Gorilla skull yet measured has a content of not more than
34-1/2 cubic inches. Let us assume, for simplicity's sake, that the
lowest Man's skull has twice the capacity of that of the highest
Gorilla. [4]
No doubt, this is a very striking difference, but it loses much of its
apparent systematic value, when viewed by the light of certain other
equally indubitable facts respecting cranial capacities.
The first of these is, that the difference in the volume of the cranial
cavity of different races of mankind is far greater, absolutely, than
that between the lowest Man and the highest Ape, while, relatively,
it is about the same. For the largest human skull measured by Morton
contained 114 cubic inches, that is to say, had very nearly double the
capacity of the smallest; while its absolute preponderance, of 52 cubic
inches--is far greater than that by which the lowest adult male human
cranium surpasses the largest of the Gorillas (62 - 34-1/2 = 27-1/2).
Secondly, the adult crania of Gorillas which have as yet been measured
differ among themselves by nearly one-third, the maximum capacity being
34.5 cubic inches, the minimum 24 cubic inches; and, thirdly, after
making all due allowance for difference of size, the cranial capacities
of some of the lower Apes fall nearly as much, relatively, below those
of the higher Apes as the latter fall below Man.
Thus, even in the important matter of cranial capacity, Men differ more
widely from one another than they do from the Apes; while the lowest
Apes differ as much, in proportion, from the highest, as the latter does
from Man. The last proposition is still better illustrated by the study
of the modifications which other parts of the cranium undergo in the
Simian series.
It is the large proportional size of the facial bones and the great
projection of the jaws which confers upon the Gorilla's skull its small
facial angle and brutal character.
[Illustration: FIG. 16.--Sections of the skulls of Man and various Apes,
drawn so as to give the cerebral cavity the same length in each case,
thereby displaying the varying proportions of the facial bones. The line
'b' indicates the plane of the tentorium, which separates the cerebrum
from the cerebellum; 'd', the axis of the occipital outlet of the skull.
The extent of cerebral cavity behind 'c', which is a perpendicular
erected on 'b' at the point where the tentorium is attached posteriorly,
indicates the degree to which the cerebrum overlaps the cerebellum--the
space occupied by which is roughly indicated by the dark shading. In
comparing these diagrams, it must be recollected, that figures on so
small a scale as these simply exemplify the statements in the text, the
proof of which is to be found in the objects themselves.]
But if we consider the proportional size of the facial bones to the
skull proper only, the little 'Chrysothrix' (Fig. 16) differs very
widely from the Gorilla, and, in the same way, as Man does; while the
Baboons ('Cynocephalus', Fig. 16) exaggerate the gross proportions of
the muzzle of the great Anthropoid, so that its visage looks mild and
human by comparison with theirs. The difference between the Gorilla and
the Baboon is even greater than it appears at first sight; for the great
facial mass of the former is largely due to a downward development of
the jaws; an essentially human character, superadded upon that almost
purely forward, essentially brutal, development of the same parts which
characterizes the Baboon, and yet more remarkably distinguishes the
Lemur.
Similarly, the occipital foramen of 'Mycetes' (Fig. 16), and still
more of the Lemurs, is situated completely in the posterior face of the
skull, or as much further back than that of the Gorilla, as that of the
Gorilla is further back than that of Man; while, as if to render patent
the futility of the attempt to base any broad classificatory distinction
on such a character, the same group of Platyrhine, or American monkeys,
to which the Mycetes belongs, contains the Chrysothrix, whose occipital
foramen is situated far more forward than in any other ape, and nearly
approaches the position it holds in Man.
Again, the Orang's skull is as devoid of excessively developed
supraciliary prominences as a Man's, though some varieties exhibit great
crests elsewhere (See pp. 231, 232); and in some of the Cebine apes and
in the 'Chrysothrix', the cranium is as smooth and rounded as that of
Man himself.
What is true of these leading characteristics of the skull, holds good,
as may be imagined, of all minor features; so that for every constant
difference between the Gorilla's skull and the Man's, a similar constant
difference of the same order (that is to say, consisting in excess or
defect of the same quality) may be found between the Gorilla's skull
and that of some other ape. So that, for the skull, no less than for the
skeleton in general, the proposition holds good, that the differences
between Man and the Gorilla are of smaller value than those between the
Gorilla and some other Apes.
In connection with the skull, I may speak of the teeth--organs which
have a peculiar classificatory value, and whose resemblances and
differences of number, form, and succession, taken as a whole, are
usually regarded as more trustworthy indicators of affinity than any
others.
[Illustration: FIG. 17.--Lateral views, of the same length, of the upper
jaws of various Primates. 'i', incisors; 'c', canines' 'pm', premolars;
'm', molars. A line is drawn through the first molar of Man, 'Gorilla',
'Cynocephalus', and 'Cebus', and the grinding surface of the second
molar is shown in each, its anterior and internal angle being just above
the 'm' of 'm2'.]
Man is provided with two sets of teeth--milk teeth and permanent teeth.
The former consist of four incisors, or cutting teeth; two canines, or
eyeteeth; and four molars, or grinders, in each jaw--making twenty in
all. The latter (Fig. 17) comprise four incisors, two canines, four
small grinders, called premolars or false molars, and six large
grinders, or true molars, in each jaw--making thirty-two in all. The
internal incisors are larger than the external pair, in the upper jaw,
smaller than the external pair, in the lower jaw. The crowns of the
upper molars exhibit four cusps, or blunt-pointed elevations, and a
ridge crosses the crown obliquely, from the inner, anterior cusp to the
outer, posterior cusp (Fig. 17 m2). The anterior lower molars have five
cusps, three external and two internal. The premolars have two cusps,
one internal and one external, of which the outer is the higher.
In all these respects the dentition of the Gorilla may be described in
the same terms as that of Man; but in other matters it exhibits many and
important differences (Fig. 17).
Thus the teeth of man constitute a regular and even series--without any
break and without any marked projection of one tooth above the level of
the rest; a peculiarity which, as Cuvier long ago showed, is shared by
no other mammal save one--as different a creature from man as can well
be imagined--namely, the long extinct 'Anoplotherium'. The teeth of
the Gorilla, on the contrary, exhibit a break, or interval, termed the
'diastema', in both jaws: in front of the eye-tooth, or between it and
the outer incisor, in the upper jaw; behind the eyetooth, or between
it and the front false molar, in the lower jaw. Into this break in the
series, in each jaw, fits the canine of the opposite jaw; the size of
the eye-tooth in the Gorilla being so great that it projects, like a
tusk, far beyond the general level of the other teeth. The roots of the
false molar teeth of the Gorilla, again, are more complex than in Man,
and the proportional size of the molars is different. The Gorilla has
the crown of the hindmost grinder of the lower jaw more complex, and
the order of eruption of the permanent teeth is different; the permanent
canines making their appearance before the second and third molars in
Man, and after them in the Gorilla.
Thus, while the teeth of the Gorilla closely resemble those of Man in
number, kind, and in the general pattern of their crowns, they exhibit
marked differences from those of Man in secondary respects, such as
relative size, number of fangs, and order of appearance.
But, if the teeth of the Gorilla be compared with those of an Ape, no
further removed from it than a 'Cynocephalus', or Baboon, it will be
found that differences and resemblances of the same order are easily
observable; but that many of the points in which the Gorilla resembles
Man are those in which it differs from the Baboon; while various
respects in which it differs from Man are exaggerated in the
'Cynocephalus'. The number and the nature of the teeth remain the same
in the Baboon as in the Gorilla and in Man. But the pattern of the
Baboon's upper molars is quite different from that described above (Fig.
17), the canines are proportionally longer and more knife-like; the
anterior premolar in the lower jaw is specially modified; the posterior
molar of the lower jaw is still larger and more complex than in the
Gorilla.
Passing from the old-world Apes to those of the new world, we meet with
a change of much greater importance than any of these. In such a genus
as 'Cebus', for example (Fig. 17), it will be found that while in
some secondary points, such as the projection of the canines and the
diastema, the resemblance to the great ape is preserved; in other and
most important respects, the dentition is extremely different. Instead
of 20 teeth in the milk set, there are 24: instead of 32 teeth in the
permanent set, there are 36, the false molars being increased from eight
to twelve. And in form, the crowns of the molars are very unlike those
of the Gorilla, and differ far more widely from the human pattern.
The Marmosets, on the other hand, exhibit the same number of teeth as
Man and the Gorilla; but, notwithstanding this, their dentition is very
different, for they have four more false molars, like the other American
monkeys--but as they have four fewer true molars, the total remains the
same. And passing from the American apes to the Lemurs, the dentition
becomes still more completely and essentially different from that of
the Gorilla. The incisors begin to vary both in number and in form. The
molars acquire, more and more, a many-pointed, insectivorous character,
and in one Genus, the Aye-Aye ('Cheiromys'), the canines disappear, and
the teeth completely simulate those of a Rodent (Fig. 17).
Hence it is obvious that, greatly as the dentition of the highest Ape
differs from that of Man, it differs far more widely from that of the
lower and lowest Apes.
Whatever part of the animal fabric--whatever series of muscles, whatever
viscera might be selected for comparison--the result would be the
same--the lower Apes and the Gorilla would differ more than the Gorilla
and the Man. I cannot attempt in this place to follow out all these
comparisons in detail, and indeed it is unnecessary I should do so. But
certain real, or supposed, structural distinctions between man and the
apes remain, upon which so much stress has been laid, that they require
careful consideration, in order that the true value may be assigned to
those which are real, and the emptiness of those which are fictitious
may be exposed. I refer to the characters of the hand, the foot, and the
brain.