The Descent Of Man

Chapter VI

ON THE AFFINITIES AND GENEALOGY OF MAN.

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

The term androgynous can be defined as the combination of partly male and partly female characteristics. It is usually used to describe a person whose gender is ambiguous. This situation may also be found in fashion. In early twentieth century because of strict social rules people used to dress according to their gender. But during world war I the gender dressing blurred and many fashion brands brought trousers for women. Click Crypto CFD Trader review to read more.

condition of the
Vertebrata–Conclusion.

Even if it be granted that the difference between man and his nearest
allies is as great in corporeal structure as some naturalists maintain, and
although we must grant that the difference between them is immense in
mental power, yet the facts given in the earlier chapters appear to
declare, in the plainest manner, that man is descended from some lower
form, notwithstanding that connecting-links have not hitherto been
discovered.

Man is liable to numerous, slight, and diversified variations, which are
induced by the same general causes, are governed and transmitted in
accordance with the same general laws, as in the lower animals. Man has
multiplied so rapidly, that he has necessarily been exposed to struggle for
existence, and consequently to natural selection. He has given rise to
many races, some of which differ so much from each other, that they have
often been ranked by naturalists as distinct species. His body is
constructed on the same homological plan as that of other mammals. He
passes through the same phases of embryological development. He retains
many rudimentary and useless structures, which no doubt were once
serviceable. Characters occasionally make their re-appearance in him,
which we have reason to believe were possessed by his early progenitors.
If the origin of man had been wholly different from that of all other
animals, these various appearances would be mere empty deceptions; but such
an admission is incredible. These appearances, on the other hand, are
intelligible, at least to a large extent, if man is the co-descendant with
other mammals of some unknown and lower form.

Some naturalists, from being deeply impressed with the mental and spiritual
powers of man, have divided the whole organic world into three kingdoms,
the Human, the Animal, and the Vegetable, thus giving to man a separate
kingdom. (1. Isidore Geoffroy St.-Hilaire gives a detailed account of the
position assigned to man by various naturalists in their classifications:
‘Hist. Nat. Gen.’ tom. ii. 1859, pp. 170-189.) Spiritual powers cannot be
compared or classed by the naturalist: but he may endeavour to shew, as I
have done, that the mental faculties of man and the lower animals do not
differ in kind, although immensely in degree. A difference in degree,
however great, does not justify us in placing man in a distinct kingdom, as
will perhaps be best illustrated by comparing the mental powers of two
insects, namely, a coccus or scale-insect and an ant, which undoubtedly
belong to the same class. The difference is here greater than, though of a
somewhat different kind from, that between man and the highest mammal. The
female coccus, whilst young, attaches itself by its proboscis to a plant;
sucks the sap, but never moves again; is fertilised and lays eggs; and this
is its whole history. On the other hand, to describe the habits and mental
powers of worker-ants, would require, as Pierre Huber has shewn, a large
volume; I may, however, briefly specify a few points. Ants certainly
communicate information to each other, and several unite for the same work,
or for games of play. They recognise their fellow-ants after months of
absence, and feel sympathy for each other. They build great edifices, keep
them clean, close the doors in the evening, and post sentries. They make
roads as well as tunnels under rivers, and temporary bridges over them, by
clinging together. They collect food for the community, and when an
object, too large for entrance, is brought to the nest, they enlarge the
door, and afterwards build it up again. They store up seeds, of which they
prevent the germination, and which, if damp, are brought up to the surface
to dry. They keep aphides and other insects as milch-cows. They go out to
battle in regular bands, and freely sacrifice their lives for the common
weal. They emigrate according to a preconcerted plan. They capture
slaves. They move the eggs of their aphides, as well as their own eggs and
cocoons, into warm parts of the nest, in order that they may be quickly
hatched; and endless similar facts could be given. (2. Some of the most
interesting facts ever published on the habits of ants are given by Mr.
Belt, in his ‘Naturalist in Nicaragua,’ 1874. See also Mr. Moggridge’s
admirable work, ‘Harvesting Ants,’ etc., 1873, also ‘L’Instinct chez les
Insectes,’ by M. George Pouchet, ‘Revue des Deux Mondes,’ Feb. 1870, p.
682.) On the whole, the difference in mental power between an ant and a
coccus is immense; yet no one has ever dreamed of placing these insects in
distinct classes, much less in distinct kingdoms. No doubt the difference
is bridged over by other insects; and this is not the case with man and the
higher apes. But we have every reason to believe that the breaks in the
series are simply the results of many forms having become extinct.

Professor Owen, relying chiefly on the structure of the brain, has divided
the mammalian series into four sub-classes. One of these he devotes to
man; in another he places both the marsupials and the Monotremata; so that
he makes man as distinct from all other mammals as are these two latter
groups conjoined. This view has not been accepted, as far as I am aware,
by any naturalist capable of forming an independent judgment, and therefore
need not here be further considered.

We can understand why a classification founded on any single character or
organ–even an organ so wonderfully complex and important as the brain–or
on the high development of the mental faculties, is almost sure to prove
unsatisfactory. This principle has indeed been tried with hymenopterous
insects; but when thus classed by their habits or instincts, the
arrangement proved thoroughly artificial. (3. Westwood, ‘Modern
Classification of Insects,’ vol. ii. 1840, p. 87.) Classifications may, of
course, be based on any character whatever, as on size, colour, or the
element inhabited; but naturalists have long felt a profound conviction
that there is a natural system. This system, it is now generally admitted,
must be, as far as possible, genealogical in arrangement,–that is, the co-
descendants of the same form must be kept together in one group, apart from
the co-descendants of any other form; but if the parent-forms are related,
so will be their descendants, and the two groups together will form a
larger group. The amount of difference between the several groups–that is
the amount of modification which each has undergone–is expressed by such
terms as genera, families, orders, and classes. As we have no record of
the lines of descent, the pedigree can be discovered only by observing the
degrees of resemblance between the beings which are to be classed. For
this object numerous points of resemblance are of much more importance than
the amount of similarity or dissimilarity in a few points. If two
languages were found to resemble each other in a multitude of words and
points of construction, they would be universally recognised as having
sprung from a common source, notwithstanding that they differed greatly in
some few words or points of construction. But with organic beings the
points of resemblance must not consist of adaptations to similar habits of
life: two animals may, for instance, have had their whole frames modified
for living in the water, and yet they will not be brought any nearer to
each other in the natural system. Hence we can see how it is that
resemblances in several unimportant structures, in useless and rudimentary
organs, or not now functionally active, or in an embryological condition,
are by far the most serviceable for classification; for they can hardly be
due to adaptations within a late period; and thus they reveal the old lines
of descent or of true affinity.

We can further see why a great amount of modification in some one character
ought not to lead us to separate widely any two organisms. A part which
already differs much from the same part in other allied forms has already,
according to the theory of evolution, varied much; consequently it would
(as long as the organism remained exposed to the same exciting conditions)
be liable to further variations of the same kind; and these, if beneficial,
would be preserved, and thus be continually augmented. In many cases the
continued development of a part, for instance, of the beak of a bird, or of
the teeth of a mammal, would not aid the species in gaining its food, or
for any other object; but with man we can see no definite limit to the
continued development of the brain and mental faculties, as far as
advantage is concerned. Therefore in determining the position of man in
the natural or genealogical system, the extreme development of his brain
ought not to outweigh a multitude of resemblances in other less important
or quite unimportant points.

The greater number of naturalists who have taken into consideration the
whole structure of man, including his mental faculties, have followed
Blumenbach and Cuvier, and have placed man in a separate Order, under the
title of the Bimana, and therefore on an equality with the orders of the
Quadrumana, Carnivora, etc. Recently many of our best naturalists have
recurred to the view first propounded by Linnaeus, so remarkable for his
sagacity, and have placed man in the same Order with the Quadrumana, under
the title of the Primates. The justice of this conclusion will be
admitted: for in the first place, we must bear in mind the comparative
insignificance for classification of the great development of the brain in
man, and that the strongly-marked differences between the skulls of man and
the Quadrumana (lately insisted upon by Bischoff, Aeby, and others)
apparently follow from their differently developed brains. In the second
place, we must remember that nearly all the other and more important
differences between man and the Quadrumana are manifestly adaptive in their
nature, and relate chiefly to the erect position of man; such as the
structure of his hand, foot, and pelvis, the curvature of his spine, and
the position of his head. The family of Seals offers a good illustration
of the small importance of adaptive characters for classification. These
animals differ from all other Carnivora in the form of their bodies and in
the structure of their limbs, far more than does man from the higher apes;
yet in most systems, from that of Cuvier to the most recent one by Mr.
Flower (4. ‘Proceedings Zoological Society,’ 1863, p. 4.), seals are
ranked as a mere family in the Order of the Carnivora. If man had not been
his own classifier, he would never have thought of founding a separate
order for his own reception.

It would be beyond my limits, and quite beyond my knowledge, even to name
the innumerable points of structure in which man agrees with the other
Primates. Our great anatomist and philosopher, Prof. Huxley, has fully
discussed this subject (5. ‘Evidence as to Man’s Place in Nature,’ 1863,
p. 70, et passim.), and concludes that man in all parts of his organization
differs less from the higher apes, than these do from the lower members of
the same group. Consequently there “is no justification for placing man in
a distinct order.”

In an early part of this work I brought forward various facts, shewing how
closely man agrees in constitution with the higher mammals; and this
agreement must depend on our close similarity in minute structure and
chemical composition. I gave, as instances, our liability to the same
diseases, and to the attacks of allied parasites; our tastes in common for
the same stimulants, and the similar effects produced by them, as well as
by various drugs, and other such facts.

As small unimportant points of resemblance between man and the Quadrumana
are not commonly noticed in systematic works, and as, when numerous, they
clearly reveal our relationship, I will specify a few such points. The
relative position of our features is manifestly the same; and the various
emotions are displayed by nearly similar movements of the muscles and skin,
chiefly above the eyebrows and round the mouth. Some few expressions are,
indeed, almost the same, as in the weeping of certain kinds of monkeys and
in the laughing noise made by others, during which the corners of the mouth
are drawn backwards, and the lower eyelids wrinkled. The external ears are
curiously alike. In man the nose is much more prominent than in most
monkeys; but we may trace the commencement of an aquiline curvature in the
nose of the Hoolock Gibbon; and this in the Semnopithecus nasica is carried
to a ridiculous extreme.

The faces of many monkeys are ornamented with beards, whiskers, or
moustaches. The hair on the head grows to a great length in some species
of Semnopithecus (6. Isidore Geoffroy St.-Hilaire, ‘Hist. Nat. Gen.’ tom.
ii. 1859, p. 217.); and in the Bonnet monkey (Macacus radiatus) it radiates
from a point on the crown, with a parting down the middle. It is commonly
said that the forehead gives to man his noble and intellectual appearance;
but the thick hair on the head of the Bonnet monkey terminates downwards
abruptly, and is succeeded by hair so short and fine that at a little
distance the forehead, with the exception of the eyebrows, appears quite
naked. It has been erroneously asserted that eyebrows are not present in
any monkey. In the species just named the degree of nakedness of the
forehead differs in different individuals; and Eschricht states (7. ‘Uber
die Richtung der Haare,’ etc., Muller’s ‘Archiv fur Anat. und Phys.’ 1837,
s. 51.) that in our children the limit between the hairy scalp and the
naked forehead is sometimes not well defined; so that here we seem to have
a trifling case of reversion to a progenitor, in whom the forehead had not
as yet become quite naked.

It is well known that the hair on our arms tends to converge from above and
below to a point at the elbow. This curious arrangement, so unlike that in
most of the lower mammals, is common to the gorilla, chimpanzee, orang,
some species of Hylobates, and even to some few American monkeys. But in
Hylobates agilis the hair on the fore-arm is directed downwards or towards
the wrist in the ordinary manner; and in H. lar it is nearly erect, with
only a very slight forward inclination; so that in this latter species it
is in a transitional state. It can hardly be doubted that with most
mammals the thickness of the hair on the back and its direction, is adapted
to throw off the rain; even the transverse hairs on the fore-legs of a dog
may serve for this end when he is coiled up asleep. Mr. Wallace, who has
carefully studied the habits of the orang, remarks that the convergence of
the hair towards the elbow on the arms of the orang may be explained as
serving to throw off the rain, for this animal during rainy weather sits
with its arms bent, and with the hands clasped round a branch or over its
head. According to Livingstone, the gorilla also “sits in pelting rain
with his hands over his head.” (8. Quoted by Reade, ‘The African Sketch
Book,’ vol i. 1873, p. 152.) If the above explanation is correct, as seems
probable, the direction of the hair on our own arms offers a curious record
of our former state; for no one supposes that it is now of any use in
throwing off the rain; nor, in our present erect condition, is it properly
directed for this purpose.

It would, however, be rash to trust too much to the principle of adaptation
in regard to the direction of the hair in man or his early progenitors; for
it is impossible to study the figures given by Eschricht of the arrangement
of the hair on the human foetus (this being the same as in the adult) and
not agree with this excellent observer that other and more complex causes
have intervened. The points of convergence seem to stand in some relation
to those points in the embryo which are last closed in during development.
There appears, also, to exist some relation between the arrangement of the
hair on the limbs, and the course of the medullary arteries. (9. On the
hair in Hylobates, see ‘Natural History of Mammals,’ by C.L. Martin, 1841,
p. 415. Also, Isidore Geoffroy on the American monkeys and other kinds,
‘Hist. Nat. Gen.’ vol. ii. 1859, pp. 216, 243. Eschricht, ibid. s. 46, 55,
61. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 619. Wallace,
‘Contributions to the Theory of Natural Selection,’ 1870, p. 344.)

It must not be supposed that the resemblances between man and certain apes
in the above and in many other points–such as in having a naked forehead,
long tresses on the head, etc.,–are all necessarily the result of unbroken
inheritance from a common progenitor, or of subsequent reversion. Many of
these resemblances are more probably due to analogous variation, which
follows, as I have elsewhere attempted to shew (10. ‘Origin of Species,’
5th edit. 1869, p.194. ‘The Variation of Animals and Plants under
Domestication,’ vol. ii. 1868, p. 348.), from co-descended organisms having
a similar constitution, and having been acted on by like causes inducing
similar modifications. With respect to the similar direction of the hair
on the fore-arms of man and certain monkeys, as this character is common to
almost all the anthropomorphous apes, it may probably be attributed to
inheritance; but this is not certain, as some very distinct American
monkeys are thus characterised.

Although, as we have now seen, man has no just right to form a separate
Order for his own reception, he may perhaps claim a distinct Sub-order or
Family. Prof. Huxley, in his last work (11. ‘An Introduction to the
Classification of Animals,’ 1869, p. 99.), divides the primates into three
Sub-orders; namely, the Anthropidae with man alone, the Simiadae including
monkeys of all kinds, and the Lemuridae with the diversified genera of
lemurs. As far as differences in certain important points of structure are
concerned, man may no doubt rightly claim the rank of a Sub-order; and this
rank is too low, if we look chiefly to his mental faculties. Nevertheless,
from a genealogical point of view it appears that this rank is too high,
and that man ought to form merely a Family, or possibly even only a Sub-
family. If we imagine three lines of descent proceeding from a common
stock, it is quite conceivable that two of them might after the lapse of
ages be so slightly changed as still to remain as species of the same
genus, whilst the third line might become so greatly modified as to deserve
to rank as a distinct Sub-family, Family, or even Order. But in this case
it is almost certain that the third line would still retain through
inheritance numerous small points of resemblance with the other two. Here,
then, would occur the difficulty, at present insoluble, how much weight we
ought to assign in our classifications to strongly-marked differences in
some few points,–that is, to the amount of modification undergone; and how
much to close resemblance in numerous unimportant points, as indicating the
lines of descent or genealogy. To attach much weight to the few but strong
differences is the most obvious and perhaps the safest course, though it
appears more correct to pay great attention to the many small resemblances,
as giving a truly natural classification.

In forming a judgment on this head with reference to man, we must glance at
the classification of the Simiadae. This family is divided by almost all
naturalists into the Catarrhine group, or Old World monkeys, all of which
are characterised (as their name expresses) by the peculiar structure of
their nostrils, and by having four premolars in each jaw; and into the
Platyrrhine group or New World monkeys (including two very distinct sub-
groups), all of which are characterised by differently constructed
nostrils, and by having six premolars in each jaw. Some other small
differences might be mentioned. Now man unquestionably belongs in his
dentition, in the structure of his nostrils, and some other respects, to
the Catarrhine or Old World division; nor does he resemble the Platyrrhines
more closely than the Catarrhines in any characters, excepting in a few of
not much importance and apparently of an adaptive nature. It is therefore
against all probability that some New World species should have formerly
varied and produced a man-like creature, with all the distinctive
characters proper to the Old World division; losing at the same time all
its own distinctive characters. There can, consequently, hardly be a doubt
that man is an off-shoot from the Old World Simian stem; and that under a
genealogical point of view he must be classed with the Catarrhine division.
(12. This is nearly the same classification as that provisionally adopted
by Mr. St. George Mivart, (‘Transactions, Philosophical Society,” 1867, p.
300), who, after separating the Lemuridae, divides the remainder of the
Primates into the Hominidae, the Simiadae which answer to the Catarrhines,
the Cebidae, and the Hapalidae,–these two latter groups answering to the
Platyrrhines. Mr. Mivart still abides by the same view; see ‘Nature,’
1871, p. 481.)

The anthropomorphous apes, namely the gorilla, chimpanzee, orang, and
hylobates, are by most naturalists separated from the other Old World
monkeys, as a distinct sub-group. I am aware that Gratiolet, relying on
the structure of the brain, does not admit the existence of this sub-group,
and no doubt it is a broken one. Thus the orang, as Mr. St. G. Mivart
remarks, “is one of the most peculiar and aberrant forms to be found in the
Order.” (13. ‘Transactions, Zoolog. Soc.’ vol. vi. 1867, p. 214.) The
remaining non-anthropomorphous Old World monkeys, are again divided by some
naturalists into two or three smaller sub-groups; the genus Semnopithecus,
with its peculiar sacculated stomach, being the type of one sub-group. But
it appears from M. Gaudry’s wonderful discoveries in Attica, that during
the Miocene period a form existed there, which connected Semnopithecus and
Macacus; and this probably illustrates the manner in which the other and
higher groups were once blended together.

If the anthropomorphous apes be admitted to form a natural sub-group, then
as man agrees with them, not only in all those characters which he
possesses in common with the whole Catarrhine group, but in other peculiar
characters, such as the absence of a tail and of callosities, and in
general appearance, we may infer that some ancient member of the
anthropomorphous sub-group gave birth to man. It is not probable that,
through the law of analogous variation, a member of one of the other lower
sub-groups should have given rise to a man-like creature, resembling the
higher anthropomorphous apes in so many respects. No doubt man, in
comparison with most of his allies, has undergone an extraordinary amount
of modification, chiefly in consequence of the great development of his
brain and his erect position; nevertheless, we should bear in mind that he
“is but one of several exceptional forms of Primates.” (14. Mr. St. G.
Mivart, ‘Transactions of the Philosophical Society,’ 1867, p. 410.)

Every naturalist, who believes in the principle of evolution, will grant
that the two main divisions of the Simiadae, namely the Catarrhine and
Platyrrhine monkeys, with their sub-groups, have all proceeded from some
one extremely ancient progenitor. The early descendants of this
progenitor, before they had diverged to any considerable extent from each
other, would still have formed a single natural group; but some of the
species or incipient genera would have already begun to indicate by their
diverging characters the future distinctive marks of the Catarrhine and
Platyrrhine divisions. Hence the members of this supposed ancient group
would not have been so uniform in their dentition, or in the structure of
their nostrils, as are the existing Catarrhine monkeys in one way and the
Platyrrhines in another way, but would have resembled in this respect the
allied Lemuridae, which differ greatly from each other in the form of their
muzzles (15. Messrs. Murie and Mivart on the Lemuroidea, ‘Transactions,
Zoological Society,’ vol. vii, 1869, p. 5.), and to an extraordinary degree
in their dentition.

The Catarrhine and Platyrrhine monkeys agree in a multitude of characters,
as is shewn by their unquestionably belonging to one and the same Order.
The many characters which they possess in common can hardly have been
independently acquired by so many distinct species; so that these
characters must have been inherited. But a naturalist would undoubtedly
have ranked as an ape or a monkey, an ancient form which possessed many
characters common to the Catarrhine and Platyrrhine monkeys, other
characters in an intermediate condition, and some few, perhaps, distinct
from those now found in either group. And as man from a genealogical point
of view belongs to the Catarrhine or Old World stock, we must conclude,
however much the conclusion may revolt our pride, that our early
progenitors would have been properly thus designated. (16. Haeckel has
come to this same conclusion. See ‘Uber die Entstehung des
Menschengeschlechts,’ in Virchow’s ‘Sammlung. gemein. wissen. Vortrage,’
1868, s. 61. Also his ‘Naturliche Schopfungsgeschicte,’ 1868, in which he
gives in detail his views on the genealogy of man.) But we must not fall
into the error of supposing that the early progenitor of the whole Simian
stock, including man, was identical with, or even closely resembled, any
existing ape or monkey.

ON THE BIRTHPLACE AND ANTIQUITY OF MAN.

We are naturally led to enquire, where was the birthplace of man at that
stage of descent when our progenitors diverged from the Catarrhine stock?
The fact that they belonged to this stock clearly shews that they inhabited
the Old World; but not Australia nor any oceanic island, as we may infer
from the laws of geographical distribution. In each great region of the
world the living mammals are closely related to the extinct species of the
same region. It is therefore probable that Africa was formerly inhabited
by extinct apes closely allied to the gorilla and chimpanzee; and as these
two species are now man’s nearest allies, it is somewhat more probable that
our early progenitors lived on the African continent than elsewhere. But
it is useless to speculate on this subject; for two or three
anthropomorphous apes, one the Dryopithecus (17. Dr. C. Forsyth Major,
‘Sur les Singes fossiles trouves en Italie:’ ‘Soc. Ital. des Sc. Nat.’ tom.
xv. 1872.) of Lartet, nearly as large as a man, and closely allied to
Hylobates, existed in Europe during the Miocene age; and since so remote a
period the earth has certainly undergone many great revolutions, and there
has been ample time for migration on the largest scale.

At the period and place, whenever and wherever it was, when man first lost
his hairy covering, he probably inhabited a hot country; a circumstance
favourable for the frugiferous diet on which, judging from analogy, he
subsisted. We are far from knowing how long ago it was when man first
diverged from the Catarrhine stock; but it may have occurred at an epoch as
remote as the Eocene period; for that the higher apes had diverged from the
lower apes as early as the Upper Miocene period is shewn by the existence
of the Dryopithecus. We are also quite ignorant at how rapid a rate
organisms, whether high or low in the scale, may be modified under
favourable circumstances; we know, however, that some have retained the
same form during an enormous lapse of time. From what we see going on
under domestication, we learn that some of the co-descendants of the same
species may be not at all, some a little, and some greatly changed, all
within the same period. Thus it may have been with man, who has undergone
a great amount of modification in certain characters in comparison with the
higher apes.

The great break in the organic chain between man and his nearest allies,
which cannot be bridged over by any extinct or living species, has often
been advanced as a grave objection to the belief that man is descended from
some lower form; but this objection will not appear of much weight to those
who, from general reasons, believe in the general principle of evolution.
Breaks often occur in all parts of the series, some being wide, sharp and
defined, others less so in various degrees; as between the orang and its
nearest allies–between the Tarsius and the other Lemuridae–between the
elephant, and in a more striking manner between the Ornithorhynchus or
Echidna, and all other mammals. But these breaks depend merely on the
number of related forms which have become extinct. At some future period,
not very distant as measured by centuries, the civilised races of man will
almost certainly exterminate, and replace, the savage races throughout the
world. At the same time the anthropomorphous apes, as Professor
Schaaffhausen has remarked (18. ‘Anthropological Review,’ April 1867, p.
236.), will no doubt be exterminated. The break between man and his
nearest allies will then be wider, for it will intervene between man in a
more civilised state, as we may hope, even than the Caucasian, and some ape
as low as a baboon, instead of as now between the negro or Australian and
the gorilla.

With respect to the absence of fossil remains, serving to connect man with
his ape-like progenitors, no one will lay much stress on this fact who
reads Sir C. Lyell’s discussion (19. ‘Elements of Geology,’ 1865, pp. 583-
585. ‘Antiquity of Man,’ 1863, p. 145.), where he shews that in all the
vertebrate classes the discovery of fossil remains has been a very slow and
fortuitous process. Nor should it be forgotten that those regions which
are the most likely to afford remains connecting man with some extinct ape-
like creature, have not as yet been searched by geologists.

LOWER STAGES IN THE GENEALOGY OF MAN.

We have seen that man appears to have diverged from the Catarrhine or Old
World division of the Simiadae, after these had diverged from the New World
division. We will now endeavour to follow the remote traces of his
genealogy, trusting principally to the mutual affinities between the
various classes and orders, with some slight reference to the periods, as
far as ascertained, of their successive appearance on the earth. The
Lemuridae stand below and near to the Simiadae, and constitute a very
distinct family of the primates, or, according to Haeckel and others, a
distinct Order. This group is diversified and broken to an extraordinary
degree, and includes many aberrant forms. It has, therefore, probably
suffered much extinction. Most of the remnants survive on islands, such as
Madagascar and the Malayan archipelago, where they have not been exposed to
so severe a competition as they would have been on well-stocked continents.
This group likewise presents many gradations, leading, as Huxley remarks
(20. ‘Man’s Place in Nature,’ p. 105.), “insensibly from the crown and
summit of the animal creation down to creatures from which there is but a
step, as it seems, to the lowest, smallest, and least intelligent of the
placental mammalia.” From these various considerations it is probable that
the Simiadae were originally developed from the progenitors of the existing
Lemuridae; and these in their turn from forms standing very low in the
mammalian series.

The Marsupials stand in many important characters below the placental
mammals. They appeared at an earlier geological period, and their range
was formerly much more extensive than at present. Hence the Placentata are
generally supposed to have been derived from the Implacentata or
Marsupials; not, however, from forms closely resembling the existing
Marsupials, but from their early progenitors. The Monotremata are plainly
allied to the Marsupials, forming a third and still lower division in the
great mammalian series. They are represented at the present day solely by
the Ornithorhynchus and Echidna; and these two forms may be safely
considered as relics of a much larger group, representatives of which have
been preserved in Australia through some favourable concurrence of
circumstances. The Monotremata are eminently interesting, as leading in
several important points of structure towards the class of reptiles.

In attempting to trace the genealogy of the Mammalia, and therefore of man,
lower down in the series, we become involved in greater and greater
obscurity; but as a most capable judge, Mr. Parker, has remarked, we have
good reason to believe, that no true bird or reptile intervenes in the
direct line of descent. He who wishes to see what ingenuity and knowledge
can effect, may consult Prof. Haeckel’s works. (21. Elaborate tables are
given in his ‘Generelle Morphologie’ (B. ii. s. cliii. and s. 425); and
with more especial reference to man in his ‘Naturliche
Schopfungsgeschichte,’ 1868. Prof. Huxley, in reviewing this latter work
(‘The Academy,’ 1869, p. 42) says, that he considers the phylum or lines of
descent of the Vertebrata to be admirably discussed by Haeckel, although he
differs on some points. He expresses, also, his high estimate of the
general tenor and spirit of the whole work.) I will content myself with a
few general remarks. Every evolutionist will admit that the five great
vertebrate classes, namely, mammals, birds, reptiles, amphibians, and
fishes, are descended from some one prototype; for they have much in
common, especially during their embryonic state. As the class of fishes is
the most lowly organised, and appeared before the others, we may conclude
that all the members of the vertebrate kingdom are derived from some
fishlike animal. The belief that animals so distinct as a monkey, an
elephant, a humming-bird, a snake, a frog, and a fish, etc., could all have
sprung from the same parents, will appear monstrous to those who have not
attended to the recent progress of natural history. For this belief
implies the former existence of links binding closely together all these
forms, now so utterly unlike.

Nevertheless, it is certain that groups of animals have existed, or do now
exist, which serve to connect several of the great vertebrate classes more
or less closely. We have seen that the Ornithorhynchus graduates towards
reptiles; and Prof. Huxley has discovered, and is confirmed by Mr. Cope and
others, that the Dinosaurians are in many important characters intermediate
between certain reptiles and certain birds–the birds referred to being the
ostrich-tribe (itself evidently a widely-diffused remnant of a larger
group) and the Archeopteryx, that strange Secondary bird, with a long
lizard-like tail. Again, according to Prof. Owen (22. ‘Palaeontology’
1860, p. 199.), the Ichthyosaurians–great sea-lizards furnished with
paddles–present many affinities with fishes, or rather, according to
Huxley, with amphibians; a class which, including in its highest division
frogs and toads, is plainly allied to the Ganoid fishes. These latter
fishes swarmed during the earlier geological periods, and were constructed
on what is called a generalised type, that is, they presented diversified
affinities with other groups of organisms. The Lepidosiren is also so
closely allied to amphibians and fishes, that naturalists long disputed in
which of these two classes to rank it; it, and also some few Ganoid fishes,
have been preserved from utter extinction by inhabiting rivers, which are
harbours of refuge, and are related to the great waters of the ocean in the
same way that islands are to continents.

Lastly, one single member of the immense and diversified class of fishes,
namely, the lancelet or amphioxus, is so different from all other fishes,
that Haeckel maintains that it ought to form a distinct class in the
vertebrate kingdom. This fish is remarkable for its negative characters;
it can hardly be said to possess a brain, vertebral column, or heart, etc.;
so that it was classed by the older naturalists amongst the worms. Many
years ago Prof. Goodsir perceived that the lancelet presented some
affinities with the Ascidians, which are invertebrate, hermaphrodite,
marine creatures permanently attached to a support. They hardly appear
like animals, and consist of a simple, tough, leathery sack, with two small
projecting orifices. They belong to the Mulluscoida of Huxley–a lower
division of the great kingdom of the Mollusca; but they have recently been
placed by some naturalists amongst the Vermes or worms. Their larvae
somewhat resemble tadpoles in shape (23. At the Falkland Islands I had the
satisfaction of seeing, in April, 1833, and therefore some years before any
other naturalist, the locomotive larvae of a compound Ascidian, closely
allied to Synoicum, but apparently generically distinct from it. The tail
was about five times as long as the oblong head, and terminated in a very
fine filament. It was, as sketched by me under a simple microscope,
plainly divided by transverse opaque partitions, which I presume represent
the great cells figured by Kovalevsky. At an early stage of development
the tail was closely coiled round the head of the larva.), and have the
power of swimming freely about. Mr. Kovalevsky (24. ‘Memoires de l’Acad.
des Sciences de St. Petersbourg,’ tom. x. No. 15, 1866.) has lately
observed that the larvae of Ascidians are related to the Vertebrata, in
their manner of development, in the relative position of the nervous
system, and in possessing a structure closely like the chorda dorsalis of
vertebrate animals; and in this he has been since confirmed by Prof.
Kupffer. M. Kovalevsky writes to me from Naples, that he has now carried
these observations yet further, and should his results be well established,
the whole will form a discovery of the very greatest value. Thus, if we
may rely on embryology, ever the safest guide in classification, it seems
that we have at last gained a clue to the source whence the Vertebrata were
derived. (25. But I am bound to add that some competent judges dispute
this conclusion; for instance, M. Giard, in a series of papers in the
‘Archives de Zoologie Experimentale,’ for 1872. Nevertheless, this
naturalist remarks, p. 281, “L’organisation de la larve ascidienne en
dehors de toute hypothese et de toute theorie, nous montre comment la
nature peut produire la disposition fondamentale du type vertebre
(l’existence d’une corde dorsale) chez un invertebre par la seule condition
vitale de l’adaptation, et cette simple possibilite du passage supprime
l’abime entre les deux sous-regnes, encore bien qu’en ignore par ou le
passage s’est fait en realite.”) We should then be justified in believing
that at an extremely remote period a group of animals existed, resembling
in many respects the larvae of our present Ascidians, which diverged into
two great branches–the one retrograding in development and producing the
present class of Ascidians, the other rising to the crown and summit of the
animal kingdom by giving birth to the Vertebrata.

We have thus far endeavoured rudely to trace the genealogy of the
Vertebrata by the aid of their mutual affinities. We will now look to man
as he exists; and we shall, I think, be able partially to restore the
structure of our early progenitors, during successive periods, but not in
due order of time. This, can be effected by means of the rudiments which
man still retains, by the characters which occasionally make their
appearance in him through reversion, and by the aid of the principles of
morphology and embryology. The various facts, to which I shall here
allude, have been given in the previous chapters.

The early progenitors of man must have been once covered with hair, both
sexes having beards; their ears were probably pointed, and capable of
movement; and their bodies were provided with a tail, having the proper
muscles. Their limbs and bodies were also acted on by many muscles which
now only occasionally reappear, but are normally present in the Quadrumana.
At this or some earlier period, the great artery and nerve of the humerus
ran through a supra-condyloid foramen. The intestine gave forth a much
larger diverticulum or caecum than that now existing. The foot was then
prehensile, judging from the condition of the great toe in the foetus; and
our progenitors, no doubt, were arboreal in their habits, and frequented
some warm, forest-clad land. The males had great canine teeth, which
served them as formidable weapons. At a much earlier period the uterus was
double; the excreta were voided through a cloaca; and the eye was protected
by a third eyelid or nictitating membrane. At a still earlier period the
progenitors of man must have been aquatic in their habits; for morphology
plainly tells us that our lungs consist of a modified swim-bladder, which
once served as a float. The clefts on the neck in the embryo of man shew
where the branchiae once existed. In the lunar or weekly recurrent periods
of some of our functions we apparently still retain traces of our
primordial birthplace, a shore washed by the tides. At about this same
early period the true kidneys were replaced by the corpora wolffiana. The
heart existed as a simple pulsating vessel; and the chorda dorsalis took
the place of a vertebral column. These early ancestors of man, thus seen
in the dim recesses of time, must have been as simply, or even still more
simply organised than the lancelet or amphioxus.

There is one other point deserving a fuller notice. It has long been known
that in the vertebrate kingdom one sex bears rudiments of various accessory
parts, appertaining to the reproductive system, which properly belong to
the opposite sex; and it has now been ascertained that at a very early
embryonic period both sexes possess true male and female glands. Hence
some remote progenitor of the whole vertebrate kingdom appears to have been
hermaphrodite or androgynous. (26. This is the conclusion of Prof.
Gegenbaur, one of the highest authorities in comparative anatomy: see
‘Grundzuge der vergleich. Anat.’ 1870, s. 876. The result has been arrived
at chiefly from the study of the Amphibia; but it appears from the
researches of Waldeyer (as quoted in ‘Journal of Anat. and Phys.’ 1869, p.
161), that the sexual organs of even “the higher vertebrata are, in their
early condition, hermaphrodite.” Similar views have long been held by some
authors, though until recently without a firm basis.) But here we
encounter a singular difficulty. In the mammalian class the males possess
rudiments of a uterus with the adjacent passage, in their vesiculae
prostaticae; they bear also rudiments of mammae, and some male Marsupials
have traces of a marsupial sack. (27. The male Thylacinus offers the best
instance. Owen, ‘Anatomy of Vertebrates,’ vol. iii. p. 771.) Other
analogous facts could be added. Are we, then, to suppose that some
extremely ancient mammal continued androgynous, after it had acquired the
chief distinctions of its class, and therefore after it had diverged from
the lower classes of the vertebrate kingdom? This seems very improbable,
for we have to look to fishes, the lowest of all the classes, to find any
still existent androgynous forms. (28. Hermaphroditism has been observed
in several species of Serranus, as well as in some other fishes, where it
is either normal and symmetrical, or abnormal and unilateral. Dr.
Zouteveen has given me references on this subject, more especially to a
paper by Prof. Halbertsma, in the ‘Transact. of the Dutch Acad. of
Sciences,’ vol. xvi. Dr. Gunther doubts the fact, but it has now been
recorded by too many good observers to be any longer disputed. Dr. M.
Lessona writes to me, that he has verified the observations made by
Cavolini on Serranus. Prof. Ercolani has recently shewn (‘Accad. delle
Scienze,’ Bologna, Dec. 28, 1871) that eels are androgynous.) That various
accessory parts, proper to each sex, are found in a rudimentary condition
in the opposite sex, may be explained by such organs having been gradually
acquired by the one sex, and then transmitted in a more or less imperfect
state to the other. When we treat of sexual selection, we shall meet with
innumerable instances of this form of transmission,–as in the case of the
spurs, plumes, and brilliant colours, acquired for battle or ornament by
male birds, and inherited by the females in an imperfect or rudimentary
condition.

The possession by male mammals of functionally imperfect mammary organs is,
in some respects, especially curious. The Monotremata have the proper
milk-secreting glands with orifices, but no nipples; and as these animals
stand at the very base of the mammalian series, it is probable that the
progenitors of the class also had milk-secreting glands, but no nipples.
This conclusion is supported by what is known of their manner of
development; for Professor Turner informs me, on the authority of Kolliker
and Langer, that in the embryo the mammary glands can be distinctly traced
before the nipples are in the least visible; and the development of
successive parts in the individual generally represents and accords with
the development of successive beings in the same line of descent. The
Marsupials differ from the Monotremata by possessing nipples; so that
probably these organs were first acquired by the Marsupials, after they had
diverged from, and risen above, the Monotremata, and were then transmitted
to the placental mammals. (29. Prof. Gegenbaur has shewn (‘Jenaische
Zeitschrift,’ Bd. vii. p. 212) that two distinct types of nipples prevail
throughout the several mammalian orders, but that it is quite intelligible
how both could have been derived from the nipples of the Marsupials, and
the latter from those of the Monotremata. See, also, a memoir by Dr. Max
Huss, on the mammary glands, ibid. B. viii. p. 176.) No one will suppose
that the marsupials still remained androgynous, after they had
approximately acquired their present structure. How then are we to account
for male mammals possessing mammae? It is possible that they were first
developed in the females and then transferred to the males, but from what
follows this is hardly probable.

It may be suggested, as another view, that long after the progenitors of
the whole mammalian class had ceased to be androgynous, both sexes yielded
milk, and thus nourished their young; and in the case of the Marsupials,
that both sexes carried their young in marsupial sacks. This will not
appear altogether improbable, if we reflect that the males of existing
syngnathous fishes receive the eggs of the females in their abdominal
pouches, hatch them, and afterwards, as some believe, nourish the young
(30. Mr. Lockwood believes (as quoted in ‘Quart. Journal of Science,’
April 1868, p. 269), from what he has observed of the development of
Hippocampus, that the walls of the abdominal pouch of the male in some way
afford nourishment. On male fishes hatching the ova in their mouths, see a
very interesting paper by Prof. Wyman, in ‘Proc. Boston Soc. of Nat. Hist.’
Sept. 15, 1857; also Prof. Turner, in ‘Journal of Anatomy and Physiology,’
Nov. 1, 1866, p. 78. Dr. Gunther has likewise described similar cases.);–
that certain other male fishes hatch the eggs within their mouths or
branchial cavities;–that certain male toads take the chaplets of eggs from
the females, and wind them round their own thighs, keeping them there until
the tadpoles are born;–that certain male birds undertake the whole duty of
incubation, and that male pigeons, as well as the females, feed their
nestlings with a secretion from their crops. But the above suggestion
first occurred to me from mammary glands of male mammals being so much more
perfectly developed than the rudiments of the other accessory reproductive
parts, which are found in the one sex though proper to the other. The
mammary glands and nipples, as they exist in male mammals, can indeed
hardly be called rudimentary; they are merely not fully developed, and not
functionally active. They are sympathetically affected under the influence
of certain diseases, like the same organs in the female. They often
secrete a few drops of milk at birth and at puberty: this latter fact
occurred in the curious case, before referred to, where a young man
possessed two pairs of mammae. In man and some other male mammals these
organs have been known occasionally to become so well developed during
maturity as to yield a fair supply of milk. Now if we suppose that during
a former prolonged period male mammals aided the females in nursing their
offspring (31. Mlle. C. Royer has suggested a similar view in her ‘Origine
de l’homme,’ etc., 1870.), and that afterwards from some cause (as from the
production of a smaller number of young) the males ceased to give this aid,
disuse of the organs during maturity would lead to their becoming inactive;
and from two well-known principles of inheritance, this state of inactivity
would probably be transmitted to the males at the corresponding age of
maturity. But at an earlier age these organs would be left unaffected, so
that they would be almost equally well developed in the young of both
sexes.

CONCLUSION.

Von Baer has defined advancement or progress in the organic scale better
than any one else, as resting on the amount of differentiation and
specialisation of the several parts of a being,–when arrived at maturity,
as I should be inclined to add. Now as organisms have become slowly
adapted to diversified lines of life by means of natural selection, their
parts will have become more and more differentiated and specialised for
various functions from the advantage gained by the division of
physiological labour. The same part appears often to have been modified
first for one purpose, and then long afterwards for some other and quite
distinct purpose; and thus all the parts are rendered more and more
complex. But each organism still retains the general type of structure of
the progenitor from which it was aboriginally derived. In accordance with
this view it seems, if we turn to geological evidence, that organisation on
the whole has advanced throughout the world by slow and interrupted steps.
In the great kingdom of the Vertebrata it has culminated in man. It must
not, however, be supposed that groups of organic beings are always
supplanted, and disappear as soon as they have given birth to other and
more perfect groups. The latter, though victorious over their
predecessors, may not have become better adapted for all places in the
economy of nature. Some old forms appear to have survived from inhabiting
protected sites, where they have not been exposed to very severe
competition; and these often aid us in constructing our genealogies, by
giving us a fair idea of former and lost populations. But we must not fall
into the error of looking at the existing members of any lowly-organised
group as perfect representatives of their ancient predecessors.

The most ancient progenitors in the kingdom of the Vertebrata, at which we
are able to obtain an obscure glance, apparently consisted of a group of
marine animals (32. The inhabitants of the seashore must be greatly
affected by the tides; animals living either about the MEAN high-water
mark, or about the MEAN low-water mark, pass through a complete cycle of
tidal changes in a fortnight. Consequently, their food supply will undergo
marked changes week by week. The vital functions of such animals, living
under these conditions for many generations, can hardly fail to run their
course in regular weekly periods. Now it is a mysterious fact that in the
higher and now terrestrial Vertebrata, as well as in other classes, many
normal and abnormal processes have one or more whole weeks as their
periods; this would be rendered intelligible if the Vertebrata are
descended from an animal allied to the existing tidal Ascidians. Many
instances of such periodic processes might be given, as the gestation of
mammals, the duration of fevers, etc. The hatching of eggs affords also a
good example, for, according to Mr. Bartlett (‘Land and Water,’ Jan. 7,
1871), the eggs of the pigeon are hatched in two weeks; those of the fowl
in three; those of the duck in four; those of the goose in five; and those
of the ostrich in seven weeks. As far as we can judge, a recurrent period,
if approximately of the right duration for any process or function, would
not, when once gained, be liable to change; consequently it might be thus
transmitted through almost any number of generations. But if the function
changed, the period would have to change, and would be apt to change almost
abruptly by a whole week. This conclusion, if sound, is highly remarkable;
for the period of gestation in each mammal, and the hatching of each bird’s
eggs, and many other vital processes, thus betray to us the primordial
birthplace of these animals.), resembling the larvae of existing Ascidians.
These animals probably gave rise to a group of fishes, as lowly organised
as the lancelet; and from these the Ganoids, and other fishes like the
Lepidosiren, must have been developed. From such fish a very small advance
would carry us on to the Amphibians. We have seen that birds and reptiles
were once intimately connected together; and the Monotremata now connect
mammals with reptiles in a slight degree. But no one can at present say by
what line of descent the three higher and related classes, namely, mammals,
birds, and reptiles, were derived from the two lower vertebrate classes,
namely, amphibians and fishes. In the class of mammals the steps are not
difficult to conceive which led from the ancient Monotremata to the ancient
Marsupials; and from these to the early progenitors of the placental
mammals. We may thus ascend to the Lemuridae; and the interval is not very
wide from these to the Simiadae. The Simiadae then branched off into two
great stems, the New World and Old World monkeys; and from the latter, at a
remote period, Man, the wonder and glory of the Universe, proceeded.

Thus we have given to man a pedigree of prodigious length, but not, it may
be said, of noble quality. The world, it has often been remarked, appears
as if it had long been preparing for the advent of man: and this, in one
sense is strictly true, for he owes his birth to a long line of
progenitors. If any single link in this chain had never existed, man would
not have been exactly what he now is. Unless we wilfully close our eyes,
we may, with our present knowledge, approximately recognise our parentage;
nor need we feel ashamed of it. The most humble organism is something much
higher than the inorganic dust under our feet; and no one with an unbiassed
mind can study any living creature, however humble, without being struck
with enthusiasm at its marvellous structure and properties.

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