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, homogeneous, structureless and formless little lumps of mucous or albuminous matter (protoplasm), like the still living Protamœba 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 assumption 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 circumstance that, according to the assertions 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 assumption of this first stage is necessary for most important general reasons.
Second Stage: Amœbæ.
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 Amœbæ (vol. i. p. [188], Fig. 2) cannot have been essentially different from these progenitors. The form value of every Amœba 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 Amœbæ, 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 Amœba. 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 primæval 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: Synamœbæ.
In order to form an approximate conception of the organisation of those ancestors of Man which first developed out of the single-celled Primæval 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 mass of simple and equi-formal Amœba-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 Amœbæ. 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 mass of homogeneous, loosely connected cells. They may be called a community of Amœbæ (Synamœbæ). (Compare p. [127].) They originated out of the single-celled Primæval animals of the second stage by repeated self-division and by the permanent union of the products of this division.
Fourth Stage: Ciliated Larva (Planæada).
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 homogeneous mass 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 larvæ (Planæa, 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: Primæval Stomach Animals (Gastræada).
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 primæval animal of the same structure, and this we have named primæval stomach animal, or Gastræa (pp. [127], [128]). These Gastræada 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 passes 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 Gastræada 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 acœlomatous worms did not as yet possess a true body-cavity (cœlom) nor blood. They originated in the early primordial period out of the Gastræada, 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 (sexual organs). The proof that human ancestors existed of a similar formation, is to be looked for in the circumstance that comparative anatomy and ontogeny point to the lower acœlomatous 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 primæval acœlomatous 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 assume 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 assume 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 cœlom) and blood in their interior. It is difficult to say which of the still living Cœlomati 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 Cœlomati, out of which the most ancient skull-less Vertebrata were directly developed. Among the Cœlomati of the present day, the Ascidians are the nearest relatives of these exceedingly remarkable Worms, which connect the widely differing classes 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 larvæ 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. It is just the position of this central spinal rod, or axial skeleton, between the dorsal marrow on the dorsal side, and the intestinal canal on the ventral side, which is most characteristic of all Vertebrate animals, including man, but also of the larvæ of the Ascidia. The form value of this stage nearly corresponds with that which the larvæ of the simple Sea-squirts possess at the time when they show the beginning of the dorsal marrow and spinal rod. (Plate [XII]. Fig. A 5: compare the explanation of these figures in the Appendix.)
SECOND HALF OF THE SERIES OF HUMAN ANCESTORS. VERTEBRATE ANIMAL ANCESTORS OF MAN
(Vertebrata).
Ninth Stage: Skull-less Animals (Acrania).
The series of human ancestors, which in accordance with their whole organisation we have to consider as Vertebrate animals, begins with the Skull-less animals, or Acrania, of whose nature the still living Lancelet (Amphioxus lanceolatus, Plate [XII]. B, XIII. B) gives us a faint idea. Since this little animal in its earliest embryonal state entirely agrees with the Ascidia, and in its further development shows itself to be a true Vertebrate animal, it forms a direct transition from the Vertebrata to the Invertebrata. Even if the human ancestors of the ninth stage in many respects differed from the Amphioxus—the last surviving representative of the Skull-less animals—yet they must have resembled it in its most essential characteristics, in the absence of head, skull, and brain. Skull-less animals of such structure—out of which animals with skulls developed at a later period—lived during the primordial period, and originated out of the Himatega of the eighth stage by the formation of the metamera, or body segments, as also by the further differentiation of all organs, especially the more perfect development of the dorsal nerve-marrow and the spinal rod lying below it. Probably the separation of the two sexes (gonochorism) also began at this stage, whereas all the previously mentioned invertebrate ancestors (apart from the 3—4 first neutral stages) exhibited the condition of hermaphrodites (hermaphroditism). (Compare vol. i. p. [196].) The certain proof of the former existence of these skull-less and brain-less ancestors of man, is furnished by the comparative anatomy and the ontogeny of the Amphioxus and of the Craniota.
Tenth Stage: Single-nostriled Animals (Monorrhina).
Out of the Skull-less ancestors of man there arose in the first place animals with skulls, or Craniota, of the most imperfect nature. The lowest stage of all still living Craniota is occupied by the class of round-mouthed animals, or Cyclostoma, namely, the Hag (Myxinoidea) and Lampreys (Petromyzontia). From the internal organization of these single-nostriled animals, or Monorrhina, we can form an approximate idea of the nature of the human ancestors of the tenth stage. In the former, as also in the latter, skull and brain must have been of the simplest form, and many important organs, as for example, the swimming bladder, the sympathetic nerve, the spleen, the jaw skeleton, and both pairs of legs, may probably as yet not have existed. However, the pouch gills and the round sucking mouth of the Cyclostoma must probably be looked upon as purely adaptive characteristics, which did not exist in the corresponding stage of ancestors. The single-nostriled animals originated during the primordial period out of the skull-less animals by the anterior end of the dorsal marrow developing into the brain, and the anterior end of the dorsal chord into the skull. The certain proof that such single-nostriled and jawless ancestors of man did exist, is found in the “comparative anatomy of the Myxinoidea.
Eleventh Stage: Primæval Fish (Selachii.).
Of all known Vertebrate animals, the ancestors of the Primæval Fish probably showed most resemblance to the still living Sharks (Squalacei). They originated out of the single-nostriled animals by the division of the single nostril into two lateral halves, by the formation of a sympathetic nervous system, a jaw skeleton, a swimming bladder, and two pairs of legs (breast fins or fore-legs, and ventral fins or hind-legs). The internal organisation of this stage may probably, upon the whole, have corresponded to the lowest species of Sharks known to us; the swimming bladder was however more strongly developed; in the case of the latter it exists only as a rudimentary organ. They lived as early as the Silurian period, as is proved by the fossil remains of sharks (teeth and fin spines) from the Silurian strata. A certain proof that the Silurian ancestors of man and of all the other double-nostriled animals were nearest akin to the Selachii, is furnished by the comparative anatomy of the latter; it shows that the relations of organisation in all Amphirrhina can be derived from those of the Selachii.
Twelfth Stage: Mud Fish (Dipneusta).
Our twelfth ancestral stage is formed by Vertebrate animals which probably possessed a remote resemblance to the still living Salamander fish (Ceratodus, Protopterus, Lepidosiren, p. [212]). They originated out of the Primæval fish (probably at the beginning of the palæolithic, or primary period) by adaptation to life on land, and by the transformation of the swimming bladder into an air-breathing lung, and of the nasal cavity (which now opened into the cavity of the mouth) into air passages. The series of the ancestors of man which breathed air through lungs began at this stage. Their organisation may probably in many respects have agreed with that of the still living Ceratodus and Protopterus, but at the same time may have been very different. They probably lived at the beginning of the Devonian period. Their existence is proved by comparative anatomy, which shows the Dipneusta to be an intermediate stage between the Selachii and Amphibia.
Thirteenth Stage: Gilled Amphibians (Sozobranchia).
Out of those Mud Fish, which we considered the primary forms of all the Vertebrata which breathe through lungs, there developed the class of Amphibia as the main line (pp. [205], [216]). Here began the five-toed formation of the foot (the Pentadactyla), which was thence transmitted to the higher Vertebrata, and finally also to Man. The gilled Amphibians must be looked upon as our most ancient ancestors of the class of Amphibia; besides possessing lungs they retained throughout life regular gills, like the still living Proteus and Axolotl (p. [218]). They originated out of the Dipneusta by the transformation of the paddling fins into five-toed legs, and also by the more perfect differentiation of various organs, especially of the vertebral column. In any case they existed about the middle of the palæolithic, or primary period, possibly even before the Coal period; for fossil Amphibia are found in coal. The proof that similar gilled Amphibians were our direct ancestors, is given by the comparative anatomy and the ontogeny of Amphibia and Mammals.
Fourteenth Stage: Tailed Amphibians (Sozura).
Our amphibious ancestors which retained their gills throughout life, were replaced at a later period by other Amphibia, which, by metamorphosis, lost the gills which they had possessed in early life, but retained the tail, as in the case of the salamanders and newts of the present day. (Compare p. [218].) They originated out of the gilled Amphibians by accustoming themselves in early life to breathe only through gills, and later in life only through lungs. They probably existed even in the second half of the primary, namely, during the Permian period, but possibly even during the Coal period. The proof of their existence lies in the fact that tailed Amphibians form a necessary intermediate link between the preceding and succeeding stages.
Fifteenth Stage: Primæval Amniota (Protamnia).
The name Protamnion we have given to the primary form of the three higher classes of Vertebrate animals, out of which the Proreptilia and the Promammalia developed as two diverging branches (p. [222]). It originated out of unknown tailed Amphibia by the complete loss of the gills, by the formation of the amnion, of the cochlea, and of the round window in the auditory organ, and of the organs of tears. It probably originated in the beginning of the mesolithic or secondary period, perhaps even towards the end of the primary, in the Permian period. The certain proof that it once existed lies in the comparative anatomy and the ontogeny of the Amniota; for all Reptiles, Birds, and Mammals, including Man, agree in so many important characteristics that they must, with full assurance, be admitted to be the descendants of a single common primary form, namely, of the Protamnion.
Sixteenth Stage: Primary Mammals (Promammalia).
We now find ourselves more at home with our ancestors. From the sixteenth up to the twenty-second stage they all belong to the large and well known class of Mammals, the confines of which we ourselves have as yet not transgressed. The common, long since extinct and unknown primary forms of all Mammalia, which we have named Promammalia, were at all events, of all still living animals, of the class most closely related to the Beaked animals, or Ornithostoma (Ornithorhynchus, Echidna, p. [233]). They differed from the latter, however, by the teeth present in their jaws. The formation of the beak in the Beaked animals of the present day must be looked upon as an adaptive characteristic which developed at a later period. The Promammalia arose out of the Protamnia (probably only at the beginning of the secondary period, namely, in the Trias) by various advances in their internal organisation, as also by the transformation of the epidermal scales into hairs, and by the formation of a mammary gland which furnished milk for the nourishment of the young ones. The certain proof that the Promammalia—inasmuch as they are the common primary forms of all Mammals—also belong to our ancestors, lies in the comparative anatomy and the ontogeny of Mammalia and Man.
Seventeenth Stage: Pouched Animals (Marsupialia).
The three sub-classes of Mammalia—as we have already seen—stand in such a relation to one another that the Marsupials, both as regards their anatomy and their ontogeny and phylogeny, form the direct transition from the Monotrema to Placental animals (p. [247]). Consequently, human ancestors must also have existed among Marsupials. They originated out of the Monotrema—which include the primary Mammalia, or Promammalia—by the division of the cloaca into the rectum and the urogenital sinus, by the formation of a nipple on the mammary gland, and by the partial suppression of the clavicles. The oldest Marsupials at all events existed as early as the Jura period (perhaps even in the Trias); during the Chalk period they passed through a series of stages preparing the way for the origin of Placentalia. The certain proof of our derivation from Marsupials—nearly akin to the still living opossum and kangaroo in their essential inner structure—is furnished by the comparative anatomy and the ontogeny of Mammalia.
Eighteenth Stage: Semi-apes (Prosimiæ).
The small group of Semi-apes, as we have already seen, is one of the most important and most interesting orders of Mammalia. It contains the direct primary forms of Genuine Apes, and thus also of Man. Our Semi-ape ancestors probably possessed only a very faint external resemblance to the still living, short-footed Semi-apes (Brachytarsi), especially the Maki, Indri, and Lori (p. [256]). They originated (probably at the beginning of the Cenolithic, or Tertiary period) out of Marsupials of Rat-like appearance by the formation of a placenta, the loss of the marsupium and the marsupial bones, and by the higher development of the commissures of the brain. The certain proof that Genuine Apes, and hence also our own race, are the direct descendants of Semi-apes, is to be found in the comparative anatomy and the ontogeny of Placental animals.
Nineteenth Stage: Tailed Apes (Menocerca).
Of the two classes of Genuine Apes which developed out of the Semi-apes, it is only the narrow-nosed, or Catarrhini, which are closely related by blood to Man. Our older ancestors from this group probably resembled the still living Nose-apes and Holy-apes (Semnopithecus), which possess jaws and narrow noses like Man, but have a long tail, and their bodies densely covered with hair (p. [271]). The Tailed Apes with narrow noses (Catarrhini Menocerci) originated out of Semi-apes by the transformation of the jaw, and by the claws on their toes becoming changed into nails; this probably took place as early as the older Tertiary period. The certain proof of our derivation from Tailed Catarrhini is to be found in the comparative anatomy and the ontogeny of Apes and of Man.
Twentieth Stage: Man-like Apes (Anthropoides).
Of all still living Apes the large tail-less, narrow-nosed Apes, namely, the Orang and Gibbon in Asia, the Gorilla and Chimpanzee in Africa, are most nearly akin to Man. It is probable that these Man-like Apes, or Anthropoides, originated during the Mid-tertiary period, namely, in the Miocene period. They developed out of the Tailed Catarrhini of the preceding stage—with which they essentially agree—by the loss of the tail, the partial loss of the hairy covering and by the excessive development of that portion of the brain just above the facial portion of the skull. There do not exist direct human ancestors among the Anthropoides of the present day, but they certainly existed among the unknown extinct Human Apes of the Miocene period. The certain proof of their former existence is furnished by the comparative anatomy of Man-like Apes and of Man.
Twenty-first Stage: Ape-like Men (Pithecanthropi).
Although the preceding ancestral stage is already so nearly akin to genuine Men that we scarcely require to assume an intermediate connecting stage, still we can look upon the speechless Primæval Men (Alali) as this intermediate link. These Ape-like men, or Pithecanthropi, very probably existed towards the end of the Tertiary period. They originated out of the Man-like Apes, or Anthropoides, by becoming completely habituated to an upright walk, and by the corresponding stronger differentiation of both pairs of legs. The fore hand of the Anthropoides became the human hand, their hinder hand became a foot for walking. Although these Ape-like Men must not merely by the external formation of their bodies, but also by their internal mental development, have been much more akin to real Men than the Man-like Apes could have been, yet they did not possess the real and chief characteristic of man, namely, the articulate human language of words, the corresponding development of a higher consciousness, and the formation of ideas. The certain proof that such Primæval Men without the power of speech, or Ape-like Men, must have preceded men possessing speech, is the result arrived at by an inquiring mind from comparative philology (from the “comparative anatomy” of language), and especially from the history of the development of language in every child (“glottal ontogenesis”) as well as in every nation (“glottal phylogenesis”).
Twenty-second Stage: Men (Homines).
Genuine Men developed out of the Ape-like Men of the preceding stage by the gradual development of the animal language of sounds into a connected or articulate language, of words. The development of this function, of course, went hand in hand with the development of its organs, namely, the higher differentiation of the larynx and the brain. The transition from speechless Ape-like Men to Genuine or Talking Men probably took place at the beginning of the Quaternary period, namely, in the Diluvial period, but possibly even at an earlier date, in the more recent Tertiary. As, according to the unanimous opinion of most eminent philologists, all human languages are not derived from a common primæval language, we must assume a polyphyletic origin of language, and in accordance with this a polyphyletic transition from speechless Ape-like Men to Genuine Men.
| ANCESTRAL SERIES OF THE HUMAN PEDIGREE. | ||||||||
| M N = Boundary between the Invertebrate and Vertebrate Ancestors. | ||||||||
| Epochs of the Organic History of the Earth. | Geological Periods of the Organic History of the Earth. | Animal Ancestral Stages of Man. | Nearest Living Relatives of the Ancestral Stages. | |||||
| I. Archilithic or Primordial Epoch |
|
| 1. | Monera (Monera) |
| Protogenes Protamœba | ||
| 2. | Single-celled Primæval animals |
| Simple Amœbæ (Automœbæ) | |||||
| 3. | Many-celled Primæval animals |
| Communities of Amœbæ (Synamœbæ) | |||||
| 4. | Ciliated planulæ (Planæada) |
| Planula larvæ | |||||
| 1. | Laurentian Period | 5. | Primæval Intestinal animals (Gastræada) |
| Gastrula larvæ | |||
| 2. | Cambrian Period | 6. | Gliding Worms (Turbellaria) |
| Rhabdocœla Dendrocœla | |||
3. | Silurian Period | 7. | Soft-worms (Scolecida) |
| ?Between the Sea-squirts and Gliding worms | |||
| 8. | Sack worms (Himatega) |
| Sea-squirts (Ascidiæ) | |||||
| M......................................................................N | ||||||||
| 9. | Skull-less (Acrania) |
| Lancelets (Amphioxi) | |||||
| 10. | Single-nostriled (Monorrhina) |
| Lampreys (Petromyzonta) | |||||
| (Compare p. [22], and Plate [XIV]. and its explanation.) | 11. | Primæval fish (Selachii) |
| Sharks (Squalacei) | ||||
| II. Palæolithic or Primary Epoch |
| 4. | Coal Period |
| 12. | Salamander fish (Dipneusta) |
| Mud fish (Protopteri) |
| 5. | Devonian Period | 13. | Gilled Amphibia (Sozobranchia) |
| (Proteus) Axolotl (Siredon) | |||
| 6. | Permian Period | 14. | Tailed Amphibia (Sozura) |
| Water-newts (Tritons) | |||
| III. Mesolithic or Secondary Epoch |
| 7. | Trias Period |
| 15. | Primæval Amniota (Protamnia) |
| ?Between the Tailed-Amphibia and Primary mammals |
| 8. | Jura Period | 16. | Primary Mammals (Promammalia) |
| Beaked animals (Monotrema) | |||
| 9. | Chalk Period Period | 17. | Pouched animals (Marsupialia) |
| Pouched rats (Didelphys) | |||
| IV. Cenolithic or Tertiary Epoch |
|
| 18. | Semi-apes (Prosimiæ) |
| Lori (Stenops) Maki (Lemur) | ||
| 10. | Eocene Period | 19. | Tailed Narrow-nosed Apes |
| Nose apes Holy apes | |||
| 11. | Miocene Period | 20. | Men-like Apes or Tail-less Narrow-nosed apes |
| Gorilla, Chimpanzee, Orang, Gibbon | |||
| 12. | Pliocene Period | 21. | Speechless Men or Ape-like Men |
| Deaf and Dumb, Cretins or Microcephali | |||
| V. Quaternary Epoch |
| 13 | Diluvial Period |
| 22. | Talking Men |
| Australians and Papuans |
| 14 | Alluvial Period | |||||||
