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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-15 05:32:06 -0700 |
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| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-15 05:32:06 -0700 |
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diff --git a/8700-h/old/chap23.html b/8700-h/old/chap23.html new file mode 100644 index 0000000..4134eaf --- /dev/null +++ b/8700-h/old/chap23.html @@ -0,0 +1,1050 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- saved from url=(0036)http://../Haeckel/The Evolution of Man --> +<html> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org"> +<title>The Evolution of Man: Title</title> +<meta content="text/html; charset=iso-8859-1" http-equiv="Content-Type"> +<meta content="MSHTML 5.00.2919.6307" name="GENERATOR"> +<link rel="stylesheet" href="haeckel.css" type="text/css"> +</head> +<body> +<center>THE EVOLUTION OF MAN<br> +Volume II<br> +<br> +<hr noshade size="1" align="center" width="10%"> +<br> +C<font size="-2">HAPTER</font> XXIII<br> +<br> +<b>OUR APE ANCESTORS</b></center> + +<br> + + +<p class="one">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 +(<i>Prochoriata</i>).</p> + +<p>The Placentals (also called <i>Choriata, Monodelphia, +Eutheria</i> or <i>Epitheria</i>) 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 <i>corpus callosum,</i> 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.</p> + +<p>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.</p> + +<p>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 <a href="chap15.html#page 165">(pp.165–9)</a> The +urinary sac or the allantois, the</p> + +<br> +<hr> +<p class="page"><a name="page 254">[ 254 ]</a></p> + +<p> </p> + +<p class="one">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. <a href= +"chap15.html#Fig. 194">Figs. 194–6).</a> 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 <a href= +"chap15.html#page 170">(p. 170).</a> 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 fœtal +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 (<i>Peramelida</i>) and all +the Placentals that the allantois develops into the distinctive and +remarkable structure that we call the <i>placenta.</i></p> + +<table class="capt" width="199" align="left" summary= +"Fig. 273. Foetal membranes of the human embryo (diagrammatic)."> +<tr> +<td align="justify"><img src="images4/fig273.GIF" width="199" +height="219" alt= +"Foetal membranes of the human embryo (diagrammatic)."> +<br><a name="Fig. 273">Fig. 273</a>—<b>Fœtal membranes of the human +embryo</b> (diagrammatic). <i>m</i> the thick muscular wall of the +womb. <i>plu</i> placenta [the inner layer (<i>plu</i>′) of +which penetrates into the chorion-villi (<i>chz</i>) with its +processes]. <i>chf</i> tufted, <i>chl</i> smooth chorion. <i>a</i> +amnion, <i>ah</i> amniotic cavity, <i>as</i> amniotic sheath of the +umbilical cord (which passes under into the navel of the +embryo—not given here), <i>dg</i> vitelline duct, <i>ds</i> +yelk sac, <i>dv, dr</i> decidua (vera and reflexa). The uterine +cavity (<i>uh</i>) opens below into the vagina and above on the +right into an oviduct (<i>t</i>). (From <i>Kölliker.</i>)</td> +</tr> +</table> + +<p>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 fœtus 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 +fœtal 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.</p> + +<p>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.</p> + +<p>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 fœtus through the umbilical +vessels (Fig. 273 <i>chz</i>). 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 (<i>plu</i>). +This network of arteries contains maternal blood, brought by the +uterine vessels. As the connective tissue between the enlarged +capillaries of</p> + +<br> +<hr> +<p class="page"><a name="page 255">[ 255 ]</a></p> + +<p> </p> + +<p class="one">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 <i>placenta.</i> The +placenta consists, therefore, properly speaking, of two different +though intimately connected parts—the fœtal placenta +(Fig. 273 <i>chz</i>) within and the maternal or uterine placenta +(<i>plu</i>) 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. <a href= +"chap15.html#Fig. 196">Fig. 196</a>).</p> + +<table class="capt" width="321" align="center" summary= +"Fig. 274. Skull of a fossil lemur (Adapis parisiensis,), from the Miocene at Quercy."> +<tr> +<td align="justify"><img src="images4/fig274.GIF" width="321" +height="109" alt= +"Skull of a fossil lemur (Adapis parisiensis,), from the Miocene at Quercy."> +<a name="Fig. 274">Fig. 274</a>—<b>Skull of a fossil +lemur</b> (<i>Adapis parisiensis</i>), from the Miocene at Quercy. +<i>A</i> lateral view from the right. <i>B</i> lower jaw, <i>C</i> +lower molar, <i>i</i> incisors, <i>c</i> canines, <i>p</i> +premolars, <i>m</i> molars.</td> +</tr> +</table> + +<p>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 <i>Indecidua,</i> and the higher Placentals or <i> +Deciduata.</i></p> + +<p>To the Indecidua belong three important groups of mammals: the +Lemurs (<i>Prosimiæ</i>), 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 fœtal 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 fœtal placenta +alone comes away; the uterine placenta is not torn away with +it.</p> + +<p>The formation of the placenta is very different in the second +and higher section of the Placentals, the <i>Deciduata.</i> 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 +(<i>chorion laeve,</i> Fig. 273 <i>chl</i>) and the thickly-tufted +chorion (<i>chorion frondosum,</i> Fig. 273 <i>chf</i>). 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 <a href= +"chap15.html#Fig. 197">(Figs. 197</a> and <a href= +"chap15.html#Fig. 200">200</a>)—namely a thick, circular disk +like a cake; so we find in the Insectivora, Chiroptera, Rodents, +and Apes. This <i>discoplacenta</i> lies on one side of the +chorion. But in the Sarcotheria (both the Carnivora and the seals, +<i>Pinnipedia</i>) and in the elephant and several other Deciduates +we find a <i>zonoplacenta</i>; 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.</p> + +<p>Still more characteristic of the Deciduates is the peculiar and +very intimate connection between the <i>chorion frondosum</i> 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 +fœtal</p> + +<br> +<hr> +<p class="page"><a name="page 256">[ 256 ]</a></p> + +<p> </p> + +<p class="one">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 fœtal membrane that is interlaced with it. +This piece is called the “falling-away” membrane +(<i>decidua</i>). 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. +<a href="chap15.html#page 168">Figs. 199, 200, pp. +168–70."</a>)</p> + +<table class="capt" width="228" align="left" summary= +"Fig. 275. The Slender Lori (Stenops gracilis) of Ceylon, a tail-less lemur."> +<tr> +<td align="center"><img src="images4/fig275.GIF" width="228" +height="352" alt= +"The Slender Lori (Stenops gracilis) of Ceylon, a tail-less lemur."> +<a name="Fig. 275">Fig. 275</a>—<b>The Slender Lori</b> +(<i>Stenops gracilis</i>) of Ceylon, a tail-less lemur."</td> +</tr> +</table> + +<p>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 fœtus 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.</p> + +<p>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 (<i>Perameles</i>) have the beginning of a +placenta. In some of the Lemurs (<i>Tarsius</i>) a discoid placenta +with decidua is developed.</p> + +<p>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 <a href= +"chap15.html#page 172">(p. 172),</a> 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 <i>Systematic Phylogeny of the +Vertebrates</i> 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 (<i>Prodidelphia</i>). 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.</p> + +<br> +<hr> +<p class="page"><a name="page 257">[ 257 ]</a></p> + +<p> </p> + +<p class="one">The primitive stem-forms of the Rodents +(<i>Esthonychida</i>), the Ungulates (<i>Chondylarthra</i>), the +Carnassia (<i>Ictopsida</i>), and the Primates (<i>Lemuravida</i>) +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 (<i>Mallotheria</i> or <i>Prochoriata</i>).</p> + +<p>Hence the great majority of the Placentals have no direct and +close relationship to man, but only the legion of the <i> +Primates.</i> This is now generally divided into three +orders—the half-apes (<i>Prosimiæ</i>), apes +(<i>Simiæ</i>), and man (<i>Anthropi</i>). The lemurs or +half-apes are the stem-group, descending from the older <i> +Mallotheria</i> of the Cretaceous period. From them the apes were +evolved in the Tertiary period, and man was formed from these +towards its close.</p> + +<p>The Lemurs (<i>Prosimiæ</i>) 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 +<i>Lemuravida</i> and the modern <i>Lemurogona.</i> The earliest +and most primitive forms of the Lemuravida are the Pachylemurs +(<i>Hypopsodina</i>); they come next to the earliest Placentals +(<i>Prochoriata</i>), and have the typical full dentition, with +forty-four teeth (3.1.4.3. over 3.1.4.3.). The Necrolemurs +(<i>Adapida,</i> Fig. 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 (<i>Autolemures</i>), 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 (<i>Macrotarsi</i>) are nearer to the Insectivora, +others again (<i>Chiromys</i>) to the Rodents. Some of the lemurs +(<i>Brachytarsi</i>) 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 <i>Megaladapis</i> of +Madagascar.</p> + +<table class="capt" width="220" align="left" summary= +"Fig. 276. The white-nosed ape (Cercopithecus petaurista)."> +<tr> +<td align="center"><img src="images4/fig276.GIF" width="220" +height="231" alt="The white-nosed ape (Cercopithecus petaurista)."> +<a name="Fig. 276">Fig. 276</a>—<b>The white-nosed ape</b> +(<i>Cercopithecus petaurista</i>).</td> +</tr> +</table> + +<p>Next to the lemurs come the true apes (<i>Simiæ</i>), 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.”</p> + +<p>In the very first exposition of his profound natural +classification (1735) Linné</p> + +<br> +<hr> +<p class="page"><a name="page 258">[ 258 ]</a></p> + +<p> </p> + +<table class="capt" width="319" align="center" summary= +"Fig. 277. The drill-baboon (Cynocephalus leucophaeus) (From Brehm.)"> +<tr> +<td align="center"><img src="images4/fig277.GIF" width="319" +height="344" alt= +"The drill-baboon (Cynocephalus leucophaeus). (From Brehm.)"> +<br><a name="Fig. 277">Fig. 277</a>—<b>The drill-baboon</b> +(<i>Cynocephalus leucophæus</i>).<br> +(From <i>Brehm.</i>)</td> +</tr> +</table> + +<p class="one">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 <i> +Bimana</i> (“two-handed”); in a second order he united +the apes and lemurs under the name of <i>Quadrumana</i> +(“four-handed”); and a third order was formed of the +distantly-related <i>Chiroptera</i> (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 <i>Man’s Place in Nature.</i> 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</p> + +<br> +<hr> +<p class="page"><a name="page 259">[ 259 ]</a></p> + +<p> </p> + +<p class="one">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.</p> + +<p>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.</p> + +<p>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 Linné’s order of the Primates (excluding +the bats), and divided it into three sub-orders, the first composed +of the half-apes (<i>Lemuridæ</i>), the second of the true +apes (<i>Simiadæ</i>), the third of men +(<i>Anthropidæ</i>).</p> + +<p>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.</p> + +<p>The order of the true apes (<i>Simiæ</i> or <i> +Pitheca</i>)—excluding the lemurs—has long been divided +into two principal groups, which also differ in their geographical +distribution. One group (<i>Hesperopitheca,</i> or western apes) +live in America. The other group, to which man belongs, are the <i> +Eopitheca</i> 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.</p> + +<p>Hence the form of dentition in man is very important. In the +fully developed</p> + +<br> +<hr> +<p class="page"><a name="page 260">[ 260 ]</a></p> + +<p> </p> + +<p class="one">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</p> + +<table class="capt" width="480" align="center" summary= +"Figs. 278 to 282. Skeletons of a man and the four anthropoid apes. Fig. 278. Gibbon (Hylobates). Fig. 279. Orang (Satyrus). Fig. 280. Chimpanzee (Anthropithecus). Fig. 281. Gorilla (Gorilla). Fig. 282. Man (Homo)."> +<tr> +<td align="center"><img src="images4/fig278.GIF" width="480" +height="294" alt="Skeletons of a man and the four anthropoid apes. Fig. 278. Gibbon (Hylobates). Fig. 279. Orang (Satyrus). Fig. 280. Chimpanzee (Anthropithecus). Fig. 281. Gorilla (Gorilla). Fig. 282. Man (Homo)."> +<a name="Fig. 278">Fig. 278</a>—<b>Skeletons of a man and the +four anthropoid apes.</b><br> +(Fig. 278, Gibbon; Fig. 279, Orang; Fig. 280, Chimpanzee; Fig. 281, Gorilla; Fig. 282, Man.<br> +(From <i>Huxley.</i>) Cf. Figs. 203–209.</td> +</tr> +</table> + +<br> +<hr> +<p class="page"><a name="page 261">[ 261 ]</a></p> + +<p> </p> + +<p class="one">“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.</p> + +<p>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 +(<i>Arctopitheca</i> or <i>Hapalidæ</i>), which include the +tamarin (<i>Midas</i>) and the brush-monkey (<i>Jacchus</i>), 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.</p> + +<p>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 (Fig. 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” +(<i>Platyrrhinæ</i>), and those of the Old World +“narrow-nosed” (<i>Catarrhinæ</i>). 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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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</p> + +<br> +<hr> +<p class="page"><a name="page 262">[ 262 ]</a></p> + +<p> </p> + +<p class="one">the comparative anatomy of man and the various +Catarrhines in his <i>Man’s Place in Nature</i> 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 (Figs. 278–282). 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).”</p> + +<p>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.</p> + +<p>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 (<i>Cynopitheca</i>) or tailed apes +(<i>Menocerca,</i> Fig. 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 <i> +Semnopitheci.</i></p> + +<p>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 XV)—the gibbon (<i>Hylobates,</i> Fig. 203) and +orang (<i>Satyrus,</i> Figs. 204, 205) in South-Eastern Asia and +the Archipelago; and the chimpanzee (<i>Anthropithecus,</i> Figs. +206, 207) and gorilla (<i>Gorilla,</i> Fig. 208) in Equatorial +Africa.</p> + +<p>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 <i>The Anthropoid Apes.</i> +Hartmann divides the primate order into two families: (1) <i> +Primarii</i> (man and the anthropoid apes); and (2) <i> +Simianæ</i> (true apes, Catarrhines and Platyrrhines). +Professor Klaatsch, of Heidelberg, has advanced a different view in +his interesting and richly illustrated work on <i>The Origin and +Development of the Human</i></p> + +<br> +<hr> +<p class="page"><a name="page 263">[ 263 ]</a></p> + +<p> </p> + +<p class="one"><i>Race.</i> This is a substantial supplement to my +<i>Anthropogeny,</i> 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 +(p. 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 <i>Archiprimus</i>; Klaatsch now +calls it <i>Primatoid.</i> Dubois has proposed the appropriate name +of <i>Prothylobates</i> for the common and much younger stem-form +of the anthropomorpha (man and the anthropoid apes). The actual <i> +Hylobates</i> 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.</p> + +<table class="capt" width="289" align="left" summary= +"Fig. 283. Skull of the fossil ape-man of Java (Pithecanthropus erectus), restored by Eugen Dubois."> +<tr> +<td align="center"><img src="images4/fig283.GIF" width="289" +height="202" alt= +"Skull of the fossil ape-man of Java (Pithecanthropus erectus), restored by Eugen Dubois."> +<a name="Fig. 283">Fig. 283</a>—<b>Skull of the fossil +ape-man of Java</b> (<i>Pithecanthropus erectus</i>), restored by +<i>Eugen Dubois.</i></td> +</tr> +</table> + +<p>Although man is directly connected with this anthropoid family +and originates from it, we may assign an important intermediate +form between the <i>Prothylobates</i> and him (the twenty-ninth +stage in our ancestry), the ape-men (<i>Pithecanthropi</i>). I gave +this name in the <i>History of Creation</i> to the +“speechless primitive men” (<i>Alali</i>), 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 <i>Pithecanthropus erectus</i> 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” (Fig. 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</p> + +<br> +<hr> +<p class="page"><a name="page 264">[ 264 ]</a></p> + +<p> </p> + +<p class="one">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 <i> +The Last Link</i>).</p> + +<p>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.</p> + +<p>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 (1897–1901) 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. +Bumüller, etc.).</p> + +<p>As the Pithecanthropus walked erect, and his brain (judging from +the capacity of his skull, Fig. 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.</p> + +<p>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 <i>Alali</i> certainly existed towards the end of the +Tertiary period, during the Pliocene, possibly even the Miocene, +period.</p> + +<p>The third, and last, stage of our animal ancestry is the true or +speaking man (<i>Homo</i>), 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 <i>History of Creation,</i> (chapter xxviii) 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.</p> + +<br> +<hr> +<p class="page"><a name="page 265">[ 265 ]</a></p> + +<p> </p> + + + +<center>SYNOPSIS OF THE CHIEF SECTIONS OF OUR STEM-HISTORY</center> + + +<br> +<center><small>First Stage: <b>The Protists</b></small></center> + +<p class="synop">Man’s ancestors are unicellular protozoa, +originally unnucleated Monera like the Chromacea, structureless +green particles of plasm; afterwards real nucleated cells (first +plasmodomous <i>Protophyta,</i> like the Palmella; then +plasmophagous <i>Protozoa,</i> like the Amœba).</p> + +<center><small>Second Stage: <b>The Blastæads</b></small></center> + +<p class="synop">Man’s ancestors are round cœnobia 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 Magospheræ +and Volvocina, equivalent to the ontogenetic blastula: hollow +globules, the wall of which consists of a single layer of ciliated +cells (blastoderm).</p> + + +<center><small>Third Stage: <b>The Gastræads</b></small></center> + +<p class="synop">Man’s ancestors are Gastræads, 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.</p> + + +<center><small>Fourth Stage: <b>The Platodes</b></small></center> + +<p class="synop">Man’s ancestors have substantially the +organisation of simple Platodes (at first like the +cryptocœlic Platodaria, later like the rhabdocœlic +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 (Figs. 239, +240).</p> + + + +<center><small>Fifth Stage: <b>The Vermalia</b></small></center> + +<p class="synop">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 (cœloma). The dorsal ectoderm +forms the vertical plate, acroganglion (Fig. 243).</p> + + + +<center><small>Sixth Stage: <b>The Prochordonia</b></small></center> + +<p class="synop">Man’s ancestors have substantially the +organisation of a simple unarticulated Chordonium (Copelata and +Ascidia-larvæ). The unsegmented chorda develops between the +dorsal medullary tube and the ventral gut-tube. The simple +cœlom-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.</p> + + + +<center><small>Seventh Stage: <b>The Acrania</b></small></center> + +<p class="synop">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.</p> + + + +<center><small>Eighth Stage: <b>The Cyclostoma</b></small></center> + +<p class="synop">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.</p> + + + +<center><small>Ninth Stage: <b>The Ichthyoda</b></small></center> + +<p class="synop">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.</p> + + + +<center><small>Tenth Stage: <b>The Amniotes</b></small></center> + +<p class="synop">Man’s ancestors are Amniotes or gill-less +Vertebrates: (1) Primitive Amniotes (Proreptilia); (2) +Sauromammals; (3) Primitive Mammals (Monotremes); (4) Marsupials; +(5) Lemurs (Prosimiæ); (6) Western apes (Platyrrhinæ); +(7) Eastern apes (Catarrhinæ): 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.</p> + +<br> + + +<hr noshade align="left" size="1" width="20%"> +<p class="ref"><a href="Title.html">Title and Contents</a><br> +<a href="title2.html">Vol. II Title and Contents</a><br> +<a href="glossary.html">Glossary</a><br> +<a href="chap22.html">Chapter XXII</a><br> +<a href="chap24.html">Chapter XXIV</a><br> +<a href="Title.html#Illustrations">Figs. 1–209</a><br> +<a href="title2.html#Illustrations">Figs. 210–408</a></p> +</body> +</html> + |