Linnaeus in his system cla.s.sed Man in the same order with genuine Apes, Semi-apes, and Bats, which he called _Primates_; that is, lords, as it were the highest dignitaries of the animal kingdom. But Blumenbach, of Gottingen, separated Man as a special order, under the name of _Bimana_, or two-handed, and contrasted him with the Apes and Semi-apes under the name of _Quadrumana_, or four-handed. This cla.s.sification was also adopted by Cuvier and, consequently, by most subsequent zoologists. It was not until 1863 that Huxley, in his excellent work, the "Evidence as to Man's Place in Nature,"(26) showed that this cla.s.sification was based upon erroneous ideas, and that the so-called "four-handed" Apes and Semi-apes are "two-handed" as much as man is himself. The difference between the foot and hand does not consist in the _physiological_ peculiarity that the first digit or thumb is opposable to the four other digits or fingers in the hand, and is not so in the foot, for there are wild tribes of men who can oppose the first or large toe to the other four, just as if it were a thumb. They can therefore use their "grasping foot" as well as a so-called "hinder hand," like Apes. The Chinese boatmen row with this hinder hand, the Bengal workmen weave with it. The Negro, in whom the big toe is especially strong and freely moveable, when climbing seizes hold of the branches of the trees with it, just like the "four-handed" Apes. Nay, even the newly born children of the most highly developed races of men, during the first months of their life, grasp as easily with the "hinder hand" as with the "fore hand,"

and hold a spoon placed in its clutch as firmly with their big toe as with the thumb! On the other hand, among the higher Apes, especially the gorilla, hand and foot are differentiated as in man. (Compare Plate IV.)

The essential difference between hand and foot is therefore not physiological, but _morphological_, and is determined by the characteristic structure of the bony skeleton and of the muscles attached to it. The ankle-bones differ from the wrist-bones in arrangement, and the foot possesses three special muscles not existing in the hand (a short flexor muscle, a short extensor muscle, and a long fibular muscle). In all these respects, Apes and Semi-apes entirely agree with man, and hence it was quite erroneous to separate him from them as a special order on account of the stronger differentiation of his hand and foot. It is the same also with all the other structural features by means of which it was attempted to distinguish Man from Apes; for example, the relative length of the limbs, the structure of the skull, of the brain, etc. In all these respects, without exception, the differences between Man and the higher Apes are less than the corresponding differences between the higher and the lower Apes. Hence Huxley, for reasons based on the most careful and most accurate anatomical comparisons, arrives at the extremely important conclusion-"Thus, whatever system of organs be studied, the comparison of their modifications in the Ape series leads to one and the same result, that the structural differences which separate Man from the Gorilla and Chimpanzee are not so great as those which separate the Gorilla from the lower Apes." In accordance with this, Huxley, strictly following the demands of logic, cla.s.ses Man, Apes, and Semi-apes in a single order, _Primates_, and divides it into the following seven families, which are of almost equal systematic value: (1) Anthropini (Man); (2) Catarrhini (genuine Apes of the Old World); (3) Platyrrhini (genuine American Apes); (4) Arctopitheci (American clawed Apes); (5) Lemurini (short-footed and long-footed Semi-apes, p. 255); (6) Chiromyini (p. 256); (7) Galeopithecini (Flying Lemurs, p. 256).

SYSTEMATIC SURVEY

_Of the Families and Genera of Apes._

-----------------+------------------------+---------------------+------------------ _Sections_ | _Families_ | _Genera_ | _Systematic Name_ _of_ | _of_ | _of_ | _of_ _Apes._ | _Apes._ | _Apes._ | _the Genera._ -----------------+------------------------+---------------------+------------------ I. APES OF THE NEW WORLD (+Hesperopitheci+), OR FLAT-NOSED APES (+Platyrrhini+).

----------------------------------------------------------------------------------- A. =Platyrrhini= { I. Silky apes { 1. Brush ape 1. Midas =with claws= { _Hapalida_ { 2. Lion ape 2. Jacchus { +Arctopitheci+ {

{ II. Flat-nosed, { 3. Squirrel ape 3. Chrysothrix { without prehensile { 4. Leaping ape 4. Callithrix B. =Platyrrhini= { tail { 5. Nocturnal ape 5. Nyctipithecus =with blunt= { _Aphyocerca_ { 6. Tail ape 6. Pithecia =nails= { { III. Flat-nosed, { 7. Rolling ape 7. Cebus +Dysmopitheci+ { with prehensile { 8. Climbing ape 8. Ateles { tail { 9. Woolly ape 9. Lagothrix { _Labidocerca_ { 10. Howling ape 10. Mycetes ---------------------------------------------------------------------------------- II. APES OF THE OLD WORLD (+Heopitheci+), OR NARROW-NOSED APES (+Catarrhini+).

---------------------------------------------------------------------------------- { IV. Tailed Catarrhini, { { with { 11. Pavian 11. Cynocephalus C. =Tailed= { cheek-pouches { 12. Macaque 12. Innus =Catarrhini= { _Ascoparea_ { 13. Sea cat 13. Cercopithecus { +Menocerca+ { V. Tailed Catarrhini, { { without { 14. Holy ape 14. Semnopithecus { cheek-pouches { 15. Short ape 15. Colobus { _Anasca_ { 16. Nose ape 16. Nasalis

{ { 17. Gibbon 17. Hylobates { VI. Human apes { 18. Orang-Outan 18. Satyrus D. =Tailless= { _Anthropoides_ { 19. Chimpanzee 19. Engeco =Catarrhini= { { 20. Gorilla 20. Gorilla { +Lipocerca+ { VII. Men { 21. Ape-like man, 21. Pithecanthropus { _Erecti_ { or speechless man (Alalus) { (_Anthropi_) { 22. Talking man 22. h.o.m.o

Straight-haired men _Lissotrichi_ | Woolly-haired men | _Ulotrichi_ | | | | | -------------v-------------/ Speechless men (_Alali_), or Ape-like men (_Pithecanthropi_) | Gorilla | _Gorilla_ | Orang Chimpanzee | | _Satyrus_ _Engeco_ | | | Gibbon | | | | _Hylobates_ | | | | | ------v------/ | | | African -------v--------/ Man-like Apes Asiatic | Man-like Apes | | ----------v-----------/ =Man-like Apes= Nose apes +Anthropoides+ _Nasalis_ | | Silk apes | Tall apes | _Arctopitheci_ | _Semnopithecus_ | | Clutch-tails | | | | _Labidocerca_ | | | | | | -v----------/ | | | Sea cat | Pavian -----v-------/ | _Cercopithecus_ | _Cynocephalus_ Flap-tails | | | | _Aphyocerca_ | | | | --------------v--------------/ =Flat-nosed Apes= Tailed Narrow-nosed apes +Platyrrhini+ _Catarrhina menocerca_ | =Narrow-nosed= | +Catarrhini+ | | | | --------------v---------------/ =Apes= +Simiae+ | | Semi-apes _Prosimiae_

If we wish to arrive at a natural system, and consequently at the pedigree of the Primates, we must go a step further still, and entirely separate the Semi-apes, or Prosimiae, (Huxley's last three families), from Genuine Apes, or Simiae (the first four families). For, as I have already shown in my General Morphology, and explained in the last chapter, the Semi-apes differ in many and important respects from Genuine Apes, and in their individual forms are more closely allied to the various other orders of Discoplacentalia. Hence the Semi-apes must probably be considered as the remnants of the common primary group, out of which the other orders of Discoplacentalia, and, it may be, all Deciduata, have developed as two diverging branches. (Gen. Morph. ii.

pp. 148 and 153.) But man cannot be separated from the order of Genuine Apes, or Simiae, as he is in every respect more closely allied to the higher Genuine Apes than the latter are to the lower Genuine Apes.

_Genuine Apes_ (Simiae) are universally divided into two perfectly natural groups, namely, the Apes of the New World, or American Apes, and the Apes of the Old World, which are indigenous to Asia and Africa, and which formerly also existed in Europe. These two cla.s.ses differ princ.i.p.ally in the formation of the nose, and they have been named accordingly. American Apes have flat noses, so that the nostrils are in front, not below; hence they are called _Flat Noses_ (Platyrrhini). On the other hand, the Apes of the Old World have a narrow cartilaginous bridge, and the nostrils turned downwards, as in man; they are, therefore, called _Narrow Noses_ (Catarrhini). Further, the jaw, which plays an important part in the cla.s.sification of Mammals, is essentially distinct in these two groups. All Catarrhinae, or Apes of the Old World, have exactly the same jaws as Man, namely, in each jaw four incisors above and below, then on each side a canine tooth and five cheek teeth, of which two are pre-molars and three molars, altogether thirty-two teeth. But all Apes of the New World, all Platyrrhini, have four more cheek teeth, namely, three pre-molars and three molars on each side, above and below: they consequently possess thirty-six teeth. Only one small group forms an exception to this rule, namely, the _Arctopitheci_, or _Clawed Apes_, in whom the third molar has degenerated, and they accordingly have on each half of their jaw three pre-molars and two molars. They also differ from the other Platyrrhini by having claws on the fingers of their hands and the toes of their feet, not nails like Man and the other Apes. This small group of South American Apes, which includes among others the well-known pretty little Midas-monkey and the Jacchus, must probably be considered only as a peculiarly developed lateral branch of the Platyrrhini.

Now, if we ask what evidence can be drawn, as to the pedigree of Apes, from the above facts, we must conclude that all the Apes of the New World have developed out of one tribe, for they all possess the characteristic jaw and the nasal formation of the Platyrrhini. In like manner it follows that all the Apes of the Old World must be derived from one and the same common primary form, which possessed the same formation of nose and jaw as all the still living Catarrhini. Further, it can scarcely be doubted that the Apes of the New World, taken as an entire tribe, are either derived from those of the Old World, or (to express it more vaguely and cautiously) both are diverging branches of one and the same tribe of Apes. We also arrive at the exceedingly important conclusion-which is of the utmost significance in regard to Man's distribution on the earth's surface-that Man _has developed out of the Catarrhini_. For we cannot discover a zoological character distinguishing him in a higher degree from the allied Apes of the Old World than that in which the most divergent forms of this group are distinguished from one another. This is the important result of Huxley's careful anatomical examination of the question, and it cannot be too highly estimated. The anatomical differences between Man and the most human-like Catarrhini (Orang, Gorilla, Chimpanzee) are in every respect less than the anatomical differences between the latter and the lowest stages of Catarrhini, more especially the Dog-like Baboon. This exceedingly important conclusion is the result of an impartial anatomical comparison of the different forms of Catarrhini.

If, therefore, we recognise the natural system of animals as the guide to our speculations, and establish upon it our pedigree, we must necessarily come to the conclusion that _the human race is a small branch of the group of Catarrhini, and has developed out of long since extinct Apes of this group in the Old World_. Some adherents of the Theory of Descent have thought that the American races of Men have developed, independently of those of the Old World, out of American Apes. I consider this hypothesis to be quite erroneous, for the complete agreement of all mankind with the Catarrhini, in regard to the characteristic formation of the nose and jaws, distinctly proves that they are of the same origin, and that they developed out of a common root after the Platyrrhini, or American Apes, had already branched off from them. The primaeval inhabitants of America, as is proved by numerous ethnographical facts, immigrated from Asia, and partly perhaps from Polynesia (or even from Europe).

There still exist great difficulties in establishing an accurate pedigree of the Human Race; this only can we further a.s.sert, that the nearest progenitors of man were tail-less Catarrhini (Lipocerca), resembling the still living Man-like Apes. These evidently developed at a late period out of tailed Catarrhini (Menocerca), the original form of Ape. Of those tail-less Catarrhini, which are now frequently called Man-like Apes, or Anthropoides, there still exist four different genera containing about a dozen different species.

The largest Man-like Ape is the famous _Gorilla_ (called Gorilla engena, or Pongo gorilla), which is indigenous to the tropics of western Africa, and was first discovered by the missionary, Dr. Savage, in 1847, on the banks of the river Gaboon. Its nearest relative is the _Chimpanzee_ (Engeco troglodytes, or Pongo troglodytes), also indigenous to western Africa, but considerably smaller than the Gorilla, which surpa.s.ses man in size and strength. The third of the three large Man-like Apes is the _Orang_, or _Orang Outang_, indigenous to Borneo and the other Sunda Islands, of which two kindred species have recently been distinguished, namely, the large Orang (Satyrus orang, or Pithecus satyrus) and the small Orang (Satyrus morio, or Pithecus morio). Lastly, there still exists in southern Asia the genus _Gibbon_ (Hylobates), of which from four to eight different species are distinguished. They are considerably smaller than the three first-named Anthropoides, and in most characteristics differ more from Man.

The tail-less Man-like Apes-especially since we have become more intimately acquainted with the Gorilla, and its connection with Man by the application of the Theory of Descent-have excited such universal interest, and called forth such a flood of writings, that there is no occasion for me here to enter into any detail about them. The reader will find their relations to Man fully discussed in the excellent works of Huxley,(26) Carl Vogt,(27) Buchner,(43) and Rolle.(28) I shall therefore confine myself to stating the most important general conclusion resulting from their thorough comparison with Man, namely, that each one of the four Man-like Apes stands nearer to Man in one or several respects than the rest, but that no one of them can in every respect be called absolutely the most like Man. The Orang stands nearest to Man in regard to the formation of the brain, the Chimpanzee in important characteristics in the formation of the skull, the Gorilla in the development of the feet and hands, and, lastly, the Gibbon in the formation of the thorax.

Thus, from a careful examination of the comparative anatomy of the Anthropoides, we obtain a similar result to that obtained by Weisbach, from a statistical cla.s.sification and a thoughtful comparison of the very numerous and careful measurements which Scherzer and Schwarz made of the different races of Men during their voyage in the Austrian frigate _Novara_ round the earth. Weisbach comprises the final result of his investigations in the following words: "_The ape-like characteristics of Man_ are by no means concentrated in one or another race, but are distributed in particular parts of the body, among the different races, in such a manner that each is endowed with some heirloom of this relationship-one race more so, another less, and even we Europeans cannot claim to be entirely free from evidences of this relationship."[5]

I must here also point out, what in fact is self-evident, that not one of all the still living Apes, and consequently not one of the so-called Man-like Apes, can be the progenitor of the Human Race. This opinion, in fact, has never been maintained by thoughtful adherents of the Theory of Descent, but it has been a.s.signed to them by their thoughtless opponents. The Ape-like progenitors of the Human Race are long since extinct. We may possibly still find their fossil bones in the tertiary rocks of southern Asia or Africa. In any case they will, in the zoological system, have to be cla.s.sed in the group of _tail-less Narrow-nosed Apes_ (Catarrhini Lipocerci, or Anthropoides).

The genealogical hypotheses, to which we have thus far been led by the application of the Theory of Descent to Man, present themselves to every clearly and logically reasoning person as the direct results from the facts of comparative anatomy, ontogeny, and palaeontology. Of course our phylogeny can indicate only in a very general way the outlines of the human pedigree. Phylogeny is the more in danger of becoming erroneous the more rigorously it is applied in detail to special animal forms known to us. However, we can, even now, with approximate certainty distinguish at least the following twenty-two stages of the ancestors of Man. Fourteen of these stages belong to the Vertebrata, and eight to the Invertebrate ancestors of Man (Prochordata.)

THE CHAIN OF THE ANIMAL ANCESTORS, OR THE SERIES OF THE PROGENITORS, OF MAN.

(Comp. Ch. XX., XXI.; Plate XIV. and p. 22.)

FIRST HALF OF THE SERIES OF THE ANCESTORS OF MAN.

INVERTEBRATE ANCESTORS OF MAN (Prochordata).

FIRST STAGE: +Monera+.

The most ancient ancestors of Man, as of all other organisms, were living creatures of the simplest kind imaginable, _organisms without organs_, like the still living Monera. They consisted of simple, h.o.m.ogeneous, structureless and formless little lumps of mucous or alb.u.minous matter (protoplasm), like the still living Protamba primitiva. (Compare vol. i. p. 186, Fig. 1.) The _form value_ of these most ancient ancestors of man was not even equal to that of a cell, but merely that of a _cytod_ (compare vol. i. p. 347); for, as in the case of all Monera, the little lump of protoplasm did not as yet possess a cell-kernel. The first of these Monera _originated_ in the beginning of the Laurentian period by _spontaneous generation_, or archigony, out of so-called "inorganic combinations," namely, out of simple combinations of carbon, oxygen, hydrogen, and nitrogen. The a.s.sumption of this spontaneous generation, that is, of a mechanical origin of the first organisms from inorganic matter, has been proved in our thirteenth chapter to be a necessary hypothesis. (Compare vol. i. p. 338.) A direct _proof_ of the earlier existence of this most ancient ancestral stage, based upon the fundamental law of biogeny, is possibly still furnished by the circ.u.mstance that, according to the a.s.sertions of many investigators, in the beginning of the development of the egg, the cell-kernel, or nucleus, disappears, and the egg-cell thus relapses to the lower stage of the cytod (Monerula, p. 124; _relapse_ of the nucleated plastid into a non-nucleated condition). The a.s.sumption of this first stage is necessary for most important general reasons.

SECOND STAGE: +Ambae+.

The second ancestral stage of Man, as of all the higher animals and plants, is formed by _a simple cell_, that is, a little piece of protoplasm enclosing a kernel. There still exist large numbers of similar "single-celled organisms." Among them the common, simple Ambae (vol. i. p. 188, Fig. 2) cannot have been essentially different from these progenitors. The _form value_ of every Amba is essentially the same as that still possessed by the egg of Man, and by the egg of all other animals. (Vol. i. p. 189, Fig. 3.) The naked egg-cells of Sponges, which creep about exactly like Ambae, cannot be distinguished from them.

The egg-cell of Man, which like that of most other animals is surrounded by a membrane, resembles an enclosed Amba. The first single-celled animals of this kind arose out of Monera by the differentiation of the inner kernel and the external protoplasm; they lived in the earlier Primordial period. An irrefutable proof that such single-celled primaeval animals really existed as the direct ancestors of Man, is furnished according to the fundamental law of biogeny (vol. i. p. 309) by the fact that the human egg is nothing more than a simple cell. (Compare p.

124.)

THIRD STAGE: +Synambae+.

In order to form an approximate conception of the organisation of those ancestors of Man which first developed out of the single-celled Primaeval animals, it is necessary to trace the changes undergone by the human egg in the beginning of its individual development. It is just here that ontogeny guides us with the greatest certainty on to the track of phylogeny. We have already seen that the egg of Man (in the same way as that of all other Mammals), after fructification has taken place, falls by self-division into a ma.s.s of simple and equi-formal Amba-like cells (vol. i. p. 190, Fig. 4 _D_). All these divided globules are at first exactly like one another, naked cells containing a kernel, but without covering; in many animals they show movements like those of the Ambae.

This ontogenetic stage of development which we called Morula (p. 125), on account of its mulberry shape, is _a certain proof_ that in the early primordial period there existed ancestors of man which possessed the _form value_ of a ma.s.s of h.o.m.ogeneous, loosely connected cells. They may be called a _community of Ambae_ (Synambae). (Compare p. 127.) They _originated_ out of the single-celled Primaeval animals of the second stage by repeated self-division and by the permanent union of the products of this division.

FOURTH STAGE: +Ciliated Larva (Planaeada)+.

In the course of the ontogenesis of most of the lower animals, and also in that of the lowest Vertebrate animals, the Lanceolate Animals, or Amphioxus, there first develops out of the Morula (Frontispiece, Fig. 3) a ciliated larva (planula). Those cells, lying on the surface of the h.o.m.ogeneous ma.s.s of cells, extend hair-like processes, or fringes of hairs, which by striking against the water keep the whole body rotating.

The round many-celled body thus becomes differentiated, in that the external cells covered with cilia differ from the non-ciliated internal cells (Frontispiece, Fig. 4). In Man and in all other Vertebrate animals (with the exception of the Amphioxus), as well as in all Arthropoda, this stage of the ciliated larva has been lost, in the course of time, by abbreviated inheritance. There must, however, have existed ancestors of Man in the early Primordial period which possessed the form value of these ciliated larvae (Planaea, p. 125). A certain proof of this is furnished by the Amphioxus, which is on the one hand related by blood to Man, but on the other has retained down to the present day the stage of the planula.

FIFTH STAGE: +Primaeval Stomach Animals (Gastraeada)+.

In the course of the individual development of Amphioxus, as well as in the most different lower animals, there first arises out of the planula the extremely important form of larva which we have named _stomach larva_, or _gastrula_ (p. 126; Frontispiece, Fig. 5, 6). According to the fundamental law of biogeny this gastrula proves the former existence of an independent form of primaeval animal of the same structure, and this we have named primaeval stomach animal, or Gastraea (pp. 127, 128).

These Gastraeada must have existed during the older Primordial period, and they must have also included the ancestors of man. A _certain proof_ of this is furnished by the Amphioxus, which in spite of its blood relationship to Man still pa.s.ses through the stage of the gastrula with a simple intestine and a double intestinal wall. (Compare Plate X.

Fig. _B 4_.)

SIXTH STAGE: +Gliding Worms (Turbellaria)+.

The human ancestors of the sixth stage which originated out of the Gastraeada of the fifth stage, were low worms, which, of all the forms of worms known to us, were most closely allied to the Gliding Worms, or Turbellaria, or at least upon the whole possessed their form value. Like the Turbellaria of the present day, the whole surface of their body was covered with cilia, and they possessed a simple body of an oval shape, entirely without appendages. These aclomatous worms did not as yet possess a true body-cavity (clom) nor blood. They _originated_ in the early primordial period out of the Gastraeada, by the formation of a middle germ-layer, or muscular layer, and also by the further differentiation of the internal parts into various organs; more especially the first formation of a nervous system, the simplest organs of sense, the simplest organs for secretion (kidneys) and generation (s.e.xual organs). The proof that human ancestors existed of a similar formation, is to be looked for in the circ.u.mstance that comparative anatomy and ontogeny point to the lower aclomatous Worms as the common primary form, not merely of all higher Worms, but also of the four higher tribes of animals. Now, of all the animals known to us, the Turbellaria, which possess neither a body-cavity nor blood, are most closely allied to these primaeval aclomatous Primary Worms.

SEVENTH STAGE: +Soft Worms (Scolecida)+.

Between the Turbellaria of the preceding stage and the Sack Worms of the next stage, we must necessarily a.s.sume at least one connecting intermediate stage. For the Tunicata, which of all known animals stand nearest to the eighth stage, and the Turbellaria which most resemble the sixth stage, indeed both belong to the lower division of the unsegmented Worms; but still these two divisions differ so much from one another in their organization, that we must necessarily a.s.sume the earlier existence of extinct intermediate forms between the two. These connecting links, of which no fossil remains exist, owing to the soft nature of their bodies, we may comprise as _Soft Worms_, or Scolecida.

They developed out of the Turbellaria of the sixth stage by forming a true body-cavity (a clom) and blood in their interior. It is difficult to say which of the still living Clomati are nearest akin to these extinct Scolecida; it may be the Acorn-worms (Balanoglossus). The proof that even the direct ancestors of man belonged to these Scolecida, is furnished by the comparative anatomy and the ontogeny of Worms and of the Amphioxus. The form value of this stage must moreover have been represented by several very different intermediate stages, in the wide gap between Turbellaria and Tunicata.

EIGHTH STAGE: +Sack Worms (Himatega)+.

Under the name of Sack worms, or Himatega, we here allude in the eighth place to those Clomati, out of which the most ancient skull-less Vertebrata were directly developed. Among the Clomati of the present day, the _Ascidians_ are the nearest relatives of these exceedingly remarkable Worms, which connect the widely differing cla.s.ses of Invertebrate and Vertebrate animals. That the ancestors of man really existed during the primordial period in the form of these Himatega, is _distinctly proved_ by the exceedingly remarkable and important agreement presented by the ontogeny of the Amphioxus and the Ascidia.

(Compare Plates XII. and XIII., also pp. 152, 200, etc.) From this fact the earlier existence of Sack Worms may be inferred; they of all known worms were most closely related to our recent Tunicates, especially to the freely swimming young forms or larvae of the simple Sea-squirts (Ascidia, Phallusia). They originated out of the worms of the seventh stage by the formation of a dorsal nerve-marrow (medulla tube), and by the formation of the spinal rod (chorda dorsalis) which lies below it.