The long series of animal forms which we must regard as the ancestors
of our race has been confined within narrower and narrower circles as
our phylogenetic inquiry has progressed. The great majority of known
animals do not fall in the line of our ancestry, and even within the
vertebrate stem only a small number are found to do so. In the most
advanced class of the stem, the mammals, there are only a few families
that belong directly to our genealogical tree. The most important of
these are the apes and their predecessors, the half-apes, and the
earliest Placentals (Prochoriata).
The Placentals (also called Choriata, Monodelphia, Eutheria or
Epitheria) are distinguished from the lower mammals we have just
considered, the Monotremes and Marsupials, by a number of striking
peculiarities. Man has all these distinctive features; that is a very
significant fact. We may, on the ground of the most careful
comparative-anatomical and ontogenetic research, formulate the thesis:
"Man is in every respect a true Placental." He has all the
characteristics of structure and development that distinguish the
Placentals from the two lower divisions of the mammals, and, in fact,
from all other animals. Among these characteristics we must especially
notice the more advanced development of the brain. The fore-brain or
cerebrum especially is much more developed in them than in the lower
animals. The corpus callosum, which forms a sort of wide bridge
connecting the two hemispheres of the cerebrum, is only fully formed
in the Placentals; it is very rudimentary in the Marsupials and
Monotremes. It is true that the lowest Placentals are not far removed
from the Marsupials in cerebral development; but within the placental
group we can trace an unbroken gradation of progressive development of
the brain, rising gradually from this lowest stage up to the elaborate
psychic organ of the apes and man. The human soul--a physiological
function of the brain--is in reality only a more advanced ape-soul.
The mammary glands of the Placentals are provided with teats like
those of the Marsupials; but we never find in the Placentals the pouch
in which the latter carry and suckle their young. Nor have they the
marsupial bones in the ventral wall at the anterior border of the
pelvis, which the Marsupials have in common with the Monotremes, and
which are formed by a partial ossification of the sinews of the inner
oblique abdominal muscle. There are merely a few insignificant
remnants of them in some of the Carnivora. The Placentals are also
generally without the hook-shaped process at the angle of the lower
jaw which is found in the Marsupials.
(FIGURE 2.273. Foetal membranes of the human embryo (diagrammatic). m
the thick muscular wall of the womb. plu placenta [the inner layer
(plu apostrophe) of which penetrates into the chorion-villi (chz) with
its processes]. chf tufted, chl smooth chorion. a amnion, ah amniotic
cavity, as amniotic sheath of the umbilical cord (which passes under
into the navel of the embryo--not given here), dg vitelline duct, ds
yelk sac, dv, dr decidua (vera and reflexa). The uterine cavity (uh)
opens below into the vagina and above on the right into an oviduct
(t). (From Kolliker.))
However, the feature that characterises the Placentals above all
others, and that has given its name to the whole sub-class, is the
formation of the placenta. We have already considered the formation
and significance of this remarkable embryonic organ when we traced the
development of the chorion and the allantois in the human embryo
(Chapter 1.15). The urinary sac or the allantois, the curious vesicle
that grows out of the hind part of the gut, has essentially the same
structure and function in the human embryo as in that of all the other
Amniotes (cf. Figures 1.194 to 1.196). There is a quite secondary
difference, on which great stress has wrongly been laid, in the fact
that in man and the higher apes the original cavity of the allantois
quickly degenerates, and the rudiment of it sticks out as a solid
projection from the primitive gut. The thin wall of the allantois
consists of the same two layers or membranes as the wall of the
gut--the gut-gland layer within and the gut-fibre layer without. In
the gut-fibre layer of the allantois there are large blood-vessels,
which serve for the nutrition, and especially the respiration, of the
embryo--the umbilical vessels (Chapter 1.15). In the reptiles and
birds the allantois enlarges into a spacious sac, which encloses the
embryo with the amnion, and does not combine with the outer foetal
membrane (the chorion). This is the case also with the lowest mammals,
the oviparous Monotremes and most of the Marsupials. It is only in
some of the later Marsupials (Peramelida) and all the Placentals that
the allantois develops into the distinctive and remarkable structure
that we call the placenta.
The placenta is formed by the branches of the blood-vessels in the
wall of the allantois growing into the hollow ectodermic tufts (villi)
of the chorion, which run into corresponding depressions in the mucous
membrane of the womb. The latter also is richly permeated with
blood-vessels which bring the mother's blood to the embryo. As the
partition in the villi between the maternal blood-vessels and those of
the foetus is extremely thin, there is a direct exchange of fluid
between the two, and this is of the greatest importance in the
nutrition of the young mammal. It is true that the maternal vessels do
not entirely pass into the foetal vessels, so that the two kinds of
blood are simply mixed. But the partition between them is so thin that
the nutritive fluid easily transudes through it. By means of this
transudation or diosmosis the exchange of fluids takes place without
difficulty. The larger the embryo is in the placentals, and the longer
it remains in the womb, the more necessary it is to have special
structures to meet its great consumption of food.
In this respect there is a very conspicuous difference between the
lower and higher mammals. In the Marsupials, in which the embryo is
only a comparatively short time in the womb and is born in a very
immature condition, the vascular arrangements in the yelk-sac and the
allantois suffice for its nutrition, as we find them in the
Monotremes, birds, and reptiles. But in the Placentals, where
gestation lasts a long time, and the embryo reaches its full
development under the protection of its enveloping membranes, there
has to be a new mechanism for the direct supply of a large quantity of
food, and this is admirably met by the formation of the placenta.
Branches of the blood-vessels penetrate into the chorion-villi from
within, starting from the gut-fibre layer of the allantois, and
bringing the blood of the foetus through the umbilical vessels (Figure
2.273 chz). On the other hand, a thick network of blood-vessels
develops in the mucous membrane that clothes the inner surface of the
womb, especially in the region of the depressions into which the
chorion-villi penetrate (plu). This network of arteries contains
maternal blood, brought by the uterine vessels. As the connective
tissue between the enlarged capillaries of the uterus disappears, wide
cavities filled with maternal blood appear, and into these the
chorion-villi of the embryo penetrate. The sum of these vessels of
both kinds, that are so intimately correlated at this point, together
with the connective and enveloping tissue, is the placenta. The
placenta consists, therefore, properly speaking, of two different
though intimately connected parts--the foetal placenta (Figure 2.273
chz) within and the maternal or uterine placenta (plu) without. The
latter is made up of the mucous coat of the uterus and its
blood-vessels, the former of the tufted chorion and the umbilical
vessels of the embryo (cf. Figure 1.196).
(FIGURE 2.274. Skull of a fossil lemur (Adapis parisiensis,), from the
Miocene at Quercy. A lateral view from the right, half natural size. B
lower jaw, C lower molar, i incisors, c canines, p premolars, m
molars.)
The manner in which these two kinds of vessels combine in the
placenta, and the structure, form, and size of it, differ a good deal
in the various Placentals; to some extent they give us valuable data
for the natural classification, and therefore the phylogeny, of the
whole of this sub-class. On the ground of these differences we divide
it into two principal sections; the lower Placentals or Indecidua, and
the higher Placentals or Deciduata.
To the Indecidua belong three important groups of mammals: the Lemurs
(Prosimiae), the Ungulates (tapirs, horses, pigs, ruminants, etc.),
and the Cetacea (dolphins and whales). In these Indecidua the villi
are distributed over the whole surface of the chorion (or its greater
part) either singly or in groups. They are only loosely connected with
the mucous coat of the uterus, so that the whole foetal membrane with
its villi can be easily withdrawn from the uterine depressions like a
hand from a glove. There is no real coalescence of the two placentas
at any part of the surface of contact. Hence at birth the foetal
placenta alone comes away; the uterine placenta is not torn away with
it.
The formation of the placenta is very different in the second and
higher section of the Placentals, the Deciduata. Here again the whole
surface of the chorion is thickly covered with the villi in the
beginning. But they afterwards disappear from one part of the surface,
and grow proportionately thicker on the other part. We thus get a
differentiation between the smooth chorion (chorion laeve, Figure
2.273 chl) and the thickly-tufted chorion (chorion frondosum, Figure
2.273 chf). The former has only a few small villi or none at all; the
latter is thickly covered with large and well-developed villi; this
alone now constitutes the placenta. In the great majority of the
Deciduata the placenta has the same shape as in man (Figures 1.197 and
1.200)--namely a thick, circular disk like a cake; so we find in the
Insectivora, Chiroptera, Rodents, and Apes. This discoplacenta lies on
one side of the chorion. But in the Sarcotheria (both the Carnivora
and the seals, Pinnipedia) and in the elephant and several other
Deciduates we find a zonoplacenta; in these the rich mass of villi
runs like a girdle round the middle of the ellipsoid chorion, the two
poles of it being free from them.
(FIGURE 2.275. The Slender Lori (Stenops gracilis) of Ceylon, a
tail-less lemur.)
Still more characteristic of the Deciduates is the peculiar and very
intimate connection between the chorion frondosum and the
corresponding part of the mucous coat of the womb, which we must
regard as a real coalescence of the two. The villi of the chorion push
their branches into the blood-filled tissues of the coat of the
uterus, and the vessels of each loop together so intimately that it is
no longer possible to separate the foetal from the maternal placenta;
they form henceforth a compact and apparently simple placenta. In
consequence of this coalescence, a whole piece of the lining of the
womb comes away at birth with the foetal membrane that is interlaced
with it. This piece is called the "falling-away" membrane (decidua).
It is also called the serous (spongy) membrane, because it is pierced
like a sieve or sponge. All the higher Placentals that have this
decidua are classed together as the "Deciduates." The tearing away of
the decidua at birth naturally causes the mother to lose a quantity of
blood, which does not happen in the Indecidua. The last part of the
uterine coat has to be repaired by a new growth after birth in the
Deciduates. (Cf. Figures 1.199 and 1.200.)
In the various orders of the Deciduates, the placenta differs
considerably both in outer form and internal structure. The extensive
investigations of the last ten years have shown that there is more
variation in these respects among the higher mammals than was formerly
supposed. The physiological work of this important embryonic organ,
the nutrition of the foetus during its long sojourn in the womb, is
accomplished in the various groups of the Placentals by very different
and sometimes very elaborate structures. They have lately been fully
described by Hans Strahl.
The phylogeny of the placenta has become more intelligible from the
fact that we have found a number of transitional forms of it. Some of
the Marsupials (Perameles) have the beginning of a placenta. In some
of the Lemurs (Tarsius) a discoid placenta with decidua is developed.
While these important results of comparative embryology have been
throwing further light on the close blood-relationship of man and the
anthropoid apes in the last few years (Chapter 1.15), the great
advance of paleontology has at the same time been affording us a
deeper insight into the stem-history of the Placental group. In the
seventh chapter of my Systematic Phylogeny of the Vertebrates I
advanced the hypothesis that the Placentals form a single stem with
many branches, which has been evolved from an older group of the
Marsupials (Prodidelphia). The four great legions of the
Placentals--Rodents, Ungulates, Carnassia, and Primates--are sharply
separated to-day by important features of organisation. But if we
consider their extinct ancestors of the Tertiary period, the
differences gradually disappear, the deeper we go in the Cenozoic
deposits; in the end we find that they vanish altogether. The
primitive stem-forms of the Rodents (Esthonychida), the Ungulates
(Chondylarthra), the Carnassia (Ictopsida), and the Primates
(Lemuravida) are so closely related at the beginning of the Tertiary
period that we might group them together as different families of one
order, the Proplacentals (Mallotheria or Prochoriata).
Hence the great majority of the Placentals have no direct and close
relationship to man, but only the legion of the Primates. This is now
generally divided into three orders--the half-apes (Prosimiae), apes
(Simiae), and man (Anthropi). The lemurs or half-apes are the
stem-group, descending from the older Mallotheria of the Cretaceous
period. From them the apes were evolved in the Tertiary period, and
man was formed from these towards its close.
The Lemurs (Prosimiae) have few living representatives. But they are
very interesting, and are the last survivors of a once extensive
group. We find many fossil remains of them in the older Tertiary
deposits of Europe and North America, in the Eocene and Miocene. We
distinguish two sub-orders, the fossil Lemuravida and the modern
Lemurogona. The earliest and most primitive forms of the Lemuravida
are the Pachylemurs (Hypopsodina); they come next to the earliest
Placentals (Prochoriata), and have the typical full dentition, with
forty-four teeth (3.1.4.3. over 3.1.4.3.). The Necrolemurs (Adapida,
Figure 2.274) have only forty teeth, and have lost an incisor in each
jaw (2.1.4.3. over 2.1.4.3.). The dentition is still further reduced
in the Lemurogona (Autolemures), which usually have only thirty-six
teeth (2.1.3.3. over 2.1.3.3.). These living survivors are scattered
far over the southern part of the Old World. Most of the species live
in Madagascar, some in the Sunda Islands, others on the mainland of
Asia and Africa. They are gloomy and melancholic animals; they live a
quiet life, climbing trees, and eating fruit and insects. They are of
different kinds. Some are closely related to the Marsupials
(especially the opossum). Others (Macrotarsi) are nearer to the
Insectivora, others again (Chiromys) to the Rodents. Some of the
lemurs (Brachytarsi) approach closely to the true apes. The numerous
fossil remains of half-apes and apes that have been recently found in
the Tertiary deposits justify us in thinking that man's ancestors were
represented by several different species during this long period. Some
of these were almost as big as men, such as the diluvial lemurogonon
Megaladapis of Madagascar.
(FIGURE 2.276. The white-nosed ape (Cercopithecus petaurista).)
Next to the lemurs come the true apes (Simiae), the twenty-sixth stage
in our ancestry. It has been beyond question for some time now that
the apes approach nearest to man in every respect of all the animals.
Just as the lowest apes come close to the lemurs, so the highest come
next to man. When we carefully study the comparative anatomy of the
apes and man, we can trace a gradual and uninterrupted advance in the
organisation of the ape up to the purely human frame, and, after
impartial examination of the "ape problem" that has been discussed of
late years with such passionate interest, we come infallibly to the
important conclusion, first formulated by Huxley in 1863: "Whatever
systems of organs we take, the comparison of their modifications in
the series of apes leads to the same result: that the anatomic
differences that separate man from the gorilla and chimpanzee are not
as great as those that separate the gorilla from the lower apes."
Translated into phylogenetic language, this "pithecometra-law,"
formulated in such masterly fashion by Huxley, is quite equivalent to
the popular saying: "Man is descended from the apes."
(FIGURE 2.277. The drill-baboon (Cynocephalus leucophaeus) (From
Brehm.))
In the very first exposition of his profound natural classification
(1735) Linne placed the anthropoid mammals at the head of the animal
kingdom, with three genera: man, the ape, and the sloth. He afterwards
called them the "Primates"--the "lords" of the animal world; he then
also separated the lemur from the true ape, and rejected the sloth.
Later zoologists divided the order of Primates. First the Gottingen
anatomist, Blumenbach, founded a special order for man, which he
called Bimana ("two-handed"); in a second order he united the apes and
lemurs under the name of Quadrumana ("four-handed"); and a third order
was formed of the distantly-related Chiroptera (bats, etc.). The
separation of the Bimana and Quadrumana was retained by Cuvier and
most of the subsequent zoologists. It seems to be extremely important,
but, as a matter of fact, it is totally wrong. This was first shown in
1863 by Huxley, in his famous Man's Place in Nature. On the strength
of careful comparative anatomical research he proved that the apes are
just as truly "two-handed" as man; or, if we prefer to reverse it,
that man is as truly four-handed as the ape. He showed convincingly
that the ideas of hand and foot had been wrongly defined, and had been
improperly based on physiological instead of morphological grounds.
The circumstance that we oppose the thumb to the other four fingers in
our hand, and so can grasp things, seemed to be a special distinction
of the hand in contrast to the foot, in which the corresponding great
toe cannot be opposed in this way to the others. But the apes can
grasp with the hind-foot as well as the fore, and so were regarded as
quadrumanous. However, the inability to grasp that we find in the foot
of civilised man is a consequence of the habit of clothing it with
tight coverings for thousands of years. Many of the bare-footed lower
races of men, especially among the negroes, use the foot very freely
in the same way as the hand. As a result of early habit and continued
practice, they can grasp with the foot (in climbing trees, for
instance) just as well as with the hand. Even new-born infants of our
own race can grasp very strongly with the great toe, and hold a spoon
with it as firmly as with the hand. Hence the physiological
distinction between hand and foot can neither be pressed very far, nor
has it a scientific basis. We must look to morphological characters.
As a matter of fact, it is possible to draw such a sharp morphological
distinction--a distinction based on anatomic structure--between the
fore and hind extremity. In the formation both of the bony skeleton
and of the muscles that are connected with the hand and foot before
and behind there are material and constant differences; and these are
found both in man and the ape. For instance, the number and
arrangement of the smaller bones of the hand and foot are quite
different. There are similar constant differences in the muscles. The
hind extremity always has three muscles (a short flexor muscle, a
short extensor muscle, and a long calf-muscle) that are not found in
the fore extremity. The arrangement of the muscles also is different
before and behind. These characteristic differences between the fore
and hind extremities are found in man as well as the ape. There can be
no doubt, therefore, that the ape's foot deserves that name just as
much as the human foot does, and that all true apes are just as
"bimanous" as man. The common distinction of the apes as
"quadrumanous" is altogether wrong morphologically.
But it may be asked whether, quite apart from this, we can find any
other features that distinguish man more sharply from the ape than the
various species of apes are distinguished from each other. Huxley gave
so complete and demonstrative a reply to this question that the
opposition still raised on many sides is absolutely without
foundation. On the ground of careful comparative anatomical research,
Huxley proved that in all morphological respects the differences
between the highest and lowest apes are greater than the corresponding
differences between the highest apes and man. He thus restored Linne's
order of the Primates (excluding the bats), and divided it into three
sub-orders, the first composed of the half-apes (Lemuridae), the
second of the true apes (Simiadae), the third of men (Anthropidae).
But, as we wish to proceed quite consistently and impartially on the
laws of systematic logic, we may, on the strength of Huxley's own law,
go a good deal farther in this division. We are justified in going at
least one important step farther, and assigning man his natural place
within one of the sections of the order of apes. All the features that
characterise this group of apes are found in man, and not found in the
other apes. We do not seem to be justified, therefore, in founding for
man a special order distinct from the apes.
The order of the true apes (Simiae or Pitheca)--excluding the
lemurs--has long been divided into two principal groups, which also
differ in their geographical distribution. One group (Hesperopitheca,
or western apes) live in America. The other group, to which man
belongs, are the Eopitheca or eastern apes; they are found in Asia and
Africa, and were formerly in Europe. All the eastern apes agree with
man in the features that are chiefly used in zoological classification
to distinguish between the two simian groups, especially in the
dentition. The objection might be raised that the teeth are too
subordinate an organ physiologically for us to lay stress on them in
so important a question. But there is a good reason for it; it is with
perfect justice that zoologists have for more than a century paid
particular attention to the teeth in the systematic division and
arrangement of the orders of mammals. The number, form, and
arrangement of the teeth are much more faithfully inherited in the
various orders than most other characters.
Hence the form of dentition in man is very important. In the fully
developed condition we have thirty-two teeth; of these eight are
incisors, four canine, and twenty molars. The eight incisors, in the
middle of the jaws, have certain characteristic differences above and
below. In the upper jaw the inner incisors are larger than the outer;
in the lower jaw the inner are the smaller. Next to these, at each
side of both jaws, is a canine (or "eye tooth"), which is larger than
the incisors. Sometimes it is very prominent in man, as it is in most
apes and many of the other mammals, and forms a sort of tusk. Next to
this there are five molars above and below on each side, the first two
of which (the "pre-molars") are small, have only one root, and are
included in the change of teeth; the three back ones are much larger,
have two roots, and only come with the second teeth. The apes of the
Old World, or all the living or fossil apes of Asia, Africa, and
Europe, have the same dentition as man.
(FIGURES 2.278 TO 2.282. Skeletons of man and the four anthropoid
apes. (From Huxley.) Cf. Figures 1.203 to 1.209.
FIGURE 2.278. Gibbon (Hylobates).
FIGURE 2.279. Orang (Satyrus).
FIGURE 2.280. Chimpanzee (Anthropithecus).
FIGURE 2.281. Gorilla (Gorilla).
FIGURE 2.282. Man (Homo).)
On the other hand, all the American apes have an additional pre-molar
in each half of the jaw. They have six molars above and below on each
side, or thirty-six teeth altogether. This characteristic difference
between the eastern and western apes has been so faithfully inherited
that it is very instructive for us. It is true that there seems to be
an exception in the case of a small family of South American apes. The
small silky apes (Arctopitheca or Hapalidae), which include the
tamarin (Midas) and the brush-monkey (Jacchus), have only five molars
in each half of the jaw (instead of six), and so seem to be nearer to
the eastern apes. But it is found, on closer examination, that they
have three premolars, like all the western apes, and that only the
last molar has been lost. Hence the apparent exception really confirms
the above distinction.
Of the other features in which the two groups of apes differ, the
structure of the nose is particularly instructive and conspicuous. All
the eastern apes have the same type of nose as man--a comparatively
narrow partition between the two halves, so that the nostrils run
downwards. In some of them the nose protrudes as far as in man, and
has the same characteristic structure. We have already alluded to the
curious long-nosed apes, which have a long, finely-curved nose. Most
of the eastern apes have, it is true, rather flat noses, like, for
instance, the white-nosed monkey (Figure 2.276); but the nasal
partition is thin and narrow in them all. The American apes have a
different type of nose. The partition is very broad and thick at the
bottom, and the wings of the nostrils are not developed, so that they
point outwards instead of downwards. This difference in the form of
the nose is so constantly inherited in both groups that the apes of
the New World are called "flat-nosed" (Platyrrhinae), and those of the
Old World "narrow-nosed" (Catarrhinae). The bony passage of the ear
(at the bottom of which is the tympanum) is short and wide in all the
Platyrrhines, but long and narrow in all the Catarrhines; and in man
this difference also is significant.
This division of the apes into Platyrrhines and Catarrhines, on the
ground of the above hereditary features, is now generally admitted in
zoology, and receives strong support from the geographical
distribution of the two groups in the east and west. It follows at
once, as regards the phylogeny of the apes, that two divergent lines
proceeded from the common stem-form of the ape-order in the early
Tertiary period, one of which spread over the Old, the other over the
New, World. It is certain that all the Platyrrhines come of one stock,
and also all the Catarrhines; but the former are phylogenetically
older, and must be regarded as the stem-group of the latter.
What can we deduce from this with regard to our own genealogy? Man has
just the same characters, the same form of dentition, auditory
passage, and nose, as all the Catarrhines; in this he radically
differs from the Platyrrhines. We are thus forced to assign him a
position among the eastern apes in the order of Primates, or at least
place him alongside of them. But it follows that man is a direct blood
relative of the apes of the Old World, and can be traced to a common
stem-form together with all the Catarrhines. In his whole organisation
and in his origin man is a true Catarrhine; he originated in the Old
World from an unknown, extinct group of the eastern apes. The apes of
the New World, or the Platyrrhines, form a divergent branch of our
genealogical tree, and this is only distantly related at its root to
the human race. We must assume, of course, that the earliest Eocene
apes had the full dentition of the Platyrrhines; hence we may regard
this stem-group as a special stage (the twenty-sixth) in our ancestry,
and deduce from it (as the twenty-seventh stage) the earliest
Catarrhines.
We have now reduced the circle of our nearest relatives to the small
and comparatively scanty group that is represented by the sub-order of
the Catarrhines; and we are in a position to answer the question of
man's place in this sub-order, and say whether we can deduce anything
further from this position as to our immediate ancestors. In answering
this question the comprehensive and able studies that Huxley gives of
the comparative anatomy of man and the various Catarrhines in his
Man's Place in Nature are of great assistance to us. It is quite clear
from these that the differences between man and the highest
Catarrhines (gorilla, chimpanzee, and orang) are in every respect
slighter than the corresponding differences between the highest and
the lowest Catarrhines (white-nosed monkey, macaco, baboon, etc.). In
fact, within the small group of the tail-less anthropoid apes the
differences between the various genera are not less than the
differences between them and man. This is seen by a glance at the
skeletons that Huxley has put together (Figures 2.278 to 2.282).
Whether we take the skull or the vertebral column or the ribs or the
fore or hind limbs, or whether we extend the comparison to the
muscles, blood-vessels, brain, placenta, etc., we always reach the
same result on impartial examination--that man is not more different
from the other Catarrhines than the extreme forms of them (for
instance, the gorilla and baboon) differ from each other. We may now,
therefore, complete the Huxleian law we have already quoted with the
following thesis: "Whatever system of organs we take, a comparison of
their modifications in the series of Catarrhines always leads to the
same conclusion; the anatomic differences that separate man from the
most advanced Catarrhines (orang, gorilla, chimpanzee) are not as
great as those that separate the latter from the lowest Catarrhines
(white-nosed monkey, macaco, baboon)."
We must, therefore, consider the descent of man from other Catarrhines
to be fully proved. Whatever further information on the comparative
anatomy and ontogeny of the living Catarrhines we may obtain in the
future, it cannot possibly disturb this conclusion. Naturally, our
Catarrhine ancestors must have passed through a long series of
different forms before the human type was produced. The chief advances
that effected this "creation of man," or his differentiation from the
nearest related Catarrhines, were: the adoption of the erect posture
and the consequent greater differentiation of the fore and hind limbs,
the evolution of articulate speech and its organ, the larynx, and the
further development of the brain and its function, the soul; sexual
selection had a great influence in this, as Darwin showed in his
famous work.
With an eye to these advances we can distinguish at least four
important stages in our simian ancestry, which represent prominent
points in the historical process of the making of man. We may take,
after the Lemurs, the earliest and lowest Platyrrhines of South
America, with thirty-six teeth, as the twenty-sixth stage of our
genealogy; they were developed from the Lemurs by a peculiar
modification of the brain, teeth, nose, and fingers. From these Eocene
stem-apes were formed the earliest Catarrhines or eastern apes, with
the human dentition (thirty-two teeth), by modification of the nose,
lengthening of the bony channel of the ear, and the loss of four
pre-molars. These oldest stem-forms of the whole Catarrhine group were
still thickly coated with hair, and had long tails--baboons
(Cynopitheca) or tailed apes (Menocerca, Figure 2.276). They lived
during the Tertiary period, and are found fossilised in the Miocene.
Of the actual tailed apes perhaps the nearest to them are the
Semnopitheci.
If we take these Semnopitheci as the twenty-seventh stage in our
ancestry, we may put next to them, as the twenty-eighth, the tail-less
anthropoid apes. This name is given to the most advanced and man-like
of the existing Catarrhines. They were developed from the other
Catarrhines by losing the tail and part of the hair, and by a higher
development of the brain, which found expression in the enormous
growth of the skull. Of this remarkable family there are only a few
genera to-day, and we have already dealt with them (Chapter 1.15)--the
gibbon (Hylobates, Figure 1.203) and orang (Satyrus, Figures 1.204 and
1.205) in South-Eastern Asia and the Archipelago; and the chimpanzee
(Anthropithecus, Figures 1.206 and 1.207) and gorilla (Gorilla, Figure
1.208) in Equatorial Africa.
The great interest that every thoughtful man takes in these nearest
relatives of ours has found expression recently in a fairly large
literature. The most distinguished of these works for impartial
treatment of the question of affinity is Robert Hartmann's little work
on The Anthropoid Apes. Hartmann divides the primate order into two
families: (1) Primarii (man and the anthropoid apes); and (2) Simianae
(true apes, Catarrhines and Platyrrhines). Professor Klaatsch, of
Heidelberg, has advanced a different view in his interesting and
richly illustrated work on The Origin and Development of the Human
Race. This is a substantial supplement to my Anthropogeny, in so far
as it gives the chief results of modern research on the early history
of man and civilisation. But when Klaatsch declares the descent of man
from the apes to be "irrational, narrow-minded, and false," in the
belief that we are thinking of some living species of ape, we must
remind him that no competent scientist has ever held so narrow a view.
All of us look merely--in the sense of Lamarck and Darwin--to the
original unity (admitted by Klaatsch) of the primate stem. This common
descent of all the Primates (men, apes, and lemurs) from one primitive
stem-form, from which the most far-reaching conclusions follow for the
whole of anthropology and philosophy, is admitted by Klaatsch as well
as by myself and all other competent zoologists who accept the theory
of evolution in general. He says explicitly (page 172): "The three
anthropoid apes--gorilla, chimpanzee, and orang--seem to be branches
from a common root, and this was not far from that of the gibbon and
man." That is in the main the opinion that I have maintained
(especially against Virchow) in a number of works ever since 1866. The
hypothetical common ancestor of all the Primates, which must have
lived in the earliest Tertiary period (more probably in the
Cretaceous), was called by me Archiprimus, Klaatsch now calls it
Primatoid. Dubois has proposed the appropriate name of Prothylobates
for the common and much younger stem-form of the anthropomorpha (man
and the anthropoid apes). The actual Hylobates is nearer to it than
the other three existing anthropoids. None of these can be said to be
absolutely the most man-like. The gorilla comes next to man in the
structure of the hand and foot, the chimpanzee in the chief features
of the skull, the orang in brain development, and the gibbon in the
formation of the chest. None of these existing anthropoid apes is
among the direct ancestors of our race; they are scattered survivors
of an ancient branch of the Catarrhines, from which the human race
developed in a particular direction.
(FIGURE 2.283. Skull of the fossil ape-man of Java (Pithecanthropus
erectus), restored by Eugen Dubois.)
Although man is directly connected with this anthropoid family and
originates from it, we may assign an important intermediate form
between the Prothylobates and him (the twenty-ninth stage in our
ancestry), the ape-men (Pithecanthropi). I gave this name in the
History of Creation to the "speechless primitive men" (Alali), which
were men in the ordinary sense as far as the general structure is
concerned (especially in the differentiation of the limbs), but lacked
one of the chief human characteristics, articulate speech and the
higher intelligence that goes with it, and so had a less developed
brain. The phylogenetic hypothesis of the organisation of this
"ape-man" which I then advanced was brilliantly confirmed twenty-four
years afterwards by the famous discovery of the fossil Pithecanthropus
erectus by Eugen Dubois (then military surgeon in Java, afterwards
professor at Amsterdam). In 1892 he found at Trinil, in the residency
of Madiun in Java, in Pliocene deposits, certain remains of a large
and very man-like ape (roof of the skull, femur, and teeth), which he
described as "an erect ape-man" and a survivor of a "stem-form of man"
(Figure 2.283). Naturally, the Pithecanthropus excited the liveliest
interest, as the long-sought transitional form between man and the
ape: we seemed to have found "the missing link." There were very
interesting scientific discussions of it at the last three
International Congresses of Zoology (Leyden, 1895, Cambridge, 1898,
and Berlin, 1901). I took an active part in the discussion at
Cambridge, and may refer the reader to the paper I read there on "The
Present Position of Our Knowledge of the Origin of Man" (translated by
Dr. Gadow with the title of The Last Link).
An extensive and valuable literature has grown up in the last ten
years on the Pithecanthropus and the pithecoid theory connected with
it. A number of distinguished anthropologists, anatomists,
paleontologists, and phylogenists have taken part in the controversy,
and made use of the important data furnished by the new science of
pre-historic research. Hermann Klaatsch has given a good summary of
them, with many fine illustrations, in the above-mentioned work. I
refer the reader to it as a valuable supplement to the present work,
especially as I cannot go any further here into these anthropological
and pre-historic questions. I will only repeat that I think he is
wrong in the attitude of hostility that he affects to take up with
regard to my own views on the descent of man from the apes.
The most powerful opponent of the pithecoid theory--and the theory of
evolution in general--during the last thirty years (until his death in
September, 1902) was the famous Berlin anatomist, Rudolf Virchow. In
the speeches which he delivered every year at various congresses and
meetings on this question, he was never tired of attacking the hated
"ape theory." His constant categorical position was: "It is quite
certain that man does not descend from the ape or any other animal."
This has been repeated incessantly by opponents of the theory,
especially theologians and philosophers. In the inaugural speech that
he delivered in 1894 at the Anthropological Congress at Vienna, he
said that "man might just as well have descended from a sheep or an
elephant as from an ape." Absurd expressions like this only show that
the famous pathological anatomist, who did so much for medicine in the
establishment of cellular pathology, had not the requisite attainments
in comparative anatomy and ontogeny, systematic zoology and
paleontology, for sound judgment in the province of anthropology. The
Strassburg anatomist, Gustav Schwalbe, deserved great praise for
having the moral courage to oppose this dogmatic and ungrounded
teaching of Virchow, and showing its untenability. The recent
admirable works of Schwalbe on the Pithecanthropus, the earliest races
of men, and the Neanderthal skull (1897 to 1901) will supply any
candid and judicious reader with the empirical material with which he
can convince himself of the baselessness of the erroneous dogmas of
Virchow and his clerical friends (J. Ranke, J. Bumuller, etc.).
As the Pithecanthropus walked erect, and his brain (judging from the
capacity of his skull, Figure 2.283) was midway between the lowest men
and the anthropoid apes, we must assume that the next great step in
the advance from the Pithecanthropus to man was the further
development of human speech and reason.
Comparative philology has recently shown that human speech is
polyphyletic in origin; that we must distinguish several (probably
many) different primitive tongues that were developed independently.
The evolution of language also teaches us (both from its ontogeny in
the child and its phylogeny in the race) that human speech proper was
only gradually developed after the rest of the body had attained its
characteristic form. It is probable that language was not evolved
until after the dispersal of the various species and races of men, and
this probably took place at the commencement of the Quaternary or
Diluvial period. The speechless ape-men or Alali certainly existed
towards the end of the Tertiary period, during the Pliocene, possibly
even the Miocene, period.
The third, and last, stage of our animal ancestry is the true or
speaking man (Homo), who was gradually evolved from the preceding
stage by the advance of animal language into articulate human speech.
As to the time and place of this real "creation of man" we can only
express tentative opinions. It was probably during the Diluvial period
in the hotter zone of the Old World, either on the mainland in
tropical Africa or Asia or on an earlier continent (Lemuria--now sunk
below the waves of the Indian Ocean), which stretched from East Africa
(Madagascar, Abyssinia) to East Asia (Sunda Islands, Further India). I
have given fully in my History of Creation, (chapter 28) the weighty
reasons for claiming this descent of man from the anthropoid eastern
apes, and shown how we may conceive the spread of the various races
from this "Paradise" over the whole earth. I have also dealt fully
with the relations of the various races and species of men to each
other.
SYNOPSIS OF THE CHIEF SECTIONS OF OUR STEM-HISTORY.
FIRST STAGE: THE PROTISTS.
Man's ancestors are unicellular protozoa, originally unnucleated
Monera like the Chromacea, structureless green particles of plasm;
afterwards real nucleated cells (first plasmodomous Protophyta, like
the Palmella; then plasmophagous Protozoa, like the Amoeba).
SECOND STAGE: THE BLASTAEADS.
Man's ancestors are round coenobia or colonies of Protozoa; they
consist of a close association of many homogeneous cells, and thus are
individuals of the second order. They resemble the round
cell-communities of the Magospherae and Volvocina, equivalent to the
ontogenetic blastula: hollow globules, the wall of which consists of a
single layer of ciliated cells (blastoderm).
THIRD STAGE: THE GASTRAEADS.
Man's ancestors are Gastraeads, like the simplest of the actual
Metazoa (Prophysema, Olynthus, Hydra, Pemmatodiscus). Their body
consists merely of a primitive gut, the wall of which is made up of
the two primary germinal layers.
FOURTH STAGE: THE PLATODES.
Man's ancestors have substantially the organisation of simple Platodes
(at first like the cryptocoelic Platodaria, later like the
rhabdocoelic Turbellaria). The leaf-shaped bilateral-symmetrical body
has only one gut-opening, and develops the first trace of a nervous
centre from the ectoderm in the middle line of the back (Figures 2.239
and 2.240).
FIFTH STAGE: THE VERMALIA.
Man's ancestors have substantially the organisation of unarticulated
Vermalia, at first Gastrotricha (Ichthydina), afterwards Frontonia
(Nemertina, Enteropneusta). Four secondary germinal layers develop,
two middle layers arising between the limiting layers (coeloma). The
dorsal ectoderm forms the vertical plate, acroganglion (Figure 2.243).
SIXTH STAGE: THE PROCHORDONIA.
Man's ancestors have substantially the organisation of a simple
unarticulated Chordonium (Copelata and Ascidia-larvae). The
unsegmented chorda develops between the dorsal medullary tube and the
ventral gut-tube. The simple coelom-pouches divide by a frontal septum
into two on each side; the dorsal pouch (episomite) forms a
muscle-plate; the ventral pouch (hyposomite) forms a gonad. Head-gut
with gill-clefts.
SEVENTH STAGE: THE ACRANIA.
Man's ancestors are skull-less Vertebrates, like the Amphioxus. The
body is a series of metamera, as several of the primitive segments are
developed. The head contains in the ventral half the branchial gut,
the trunk the hepatic gut. The medullary tube is still simple. No
skull, jaws, or limbs.
EIGHTH STAGE: THE CYCLOSTOMA.
Man's ancestors are jaw-less Craniotes (like the Myxinoida and
Petromyzonta). The number of metamera increases. The fore-end of the
medullary tube expands into a vesicle and forms the brain, which soon
divides into five cerebral vesicles. In the sides of it appear the
three higher sense-organs: nose, eyes, and auditory vesicles. No jaws,
limbs, or floating bladder.
NINTH STAGE: THE ICHTHYODA.
Man's ancestors are fish-like Craniotes: (1) Primitive fishes
(Selachii); (2) plated fishes (Ganoida); (3) amphibian fishes
(Dipneusta); (4) mailed amphibia (Stegocephala). The ancestors of this
series develop two pairs of limbs: a pair of fore (breast-fins) and of
hind (belly-fins) legs. The gill-arches are formed between the
gill-clefts: the first pair form the maxillary arches (the upper and
lower jaws). The floating bladder (lung) and pancreas grow out of the
gut.
TENTH STAGE: THE AMNIOTES.
Man's ancestors are Amniotes or gill-less Vertebrates: (1) Primitive
Amniotes (Proreptilia); (2) Sauromammals; (3) Primitive Mammals
(Monotremes); (4) Marsupials; (5) Lemurs (Prosimiae); (6) Western apes
(Platyrrhinae); (7) Eastern apes (Catarrhinae): at first tailed
Cynopitheca; then tail-less anthropoids; later speechless ape-men
(Alali); finally speaking man. The ancestors of these Amniotes develop
an amnion and allantois, and gradually assume the mammal, and finally
the specifically human, form.