The American Journal of Science/Series 4, Volume 4/On Pithecanthropus erectus

by Léonce-Pierre Manouvrier

Art. XXIV.—On Pithecanthropus erectus; by Professor L. Manouvrier of the Paris School of Anthropology.^[1]

Extracts selected from two articles: "The Pithecanthropus erectus and the Theory of Evolution" (Revue Scientifique, 4^me sér., t. v), and "Response to the Objections against the Pithecanthropus" (Bull. de la Soc. d'Anthrop. de Paris, 4^me sér., t. vii). Translated by George Grant MacCurdy, M.A.

The Revue has already said a few words about an important scientific event which I now propose to discuss more fully.

It is a question of the discovery in Tertiary strata near Trinil, Java, of bones which seem to have belonged to a being intermediate between man and the anthropoids. This could be a precursor and perhaps an immediate ancestor of the human species, the link, heretofore lacking, of the chain which, according to the theory of evolution, ought to unite without interruption Homo sapiens with the rest of the animal kingdom. The author of this discovery is Mr. Eugene Dubois, physician in the Dutch army. The occasion was a vast geologic exploration made in Java, from 1890 to 1895, under the auspices of the government of Holland.

Such good fortune did not come to Mr. Dubois by hazard. He was attracted to the Indian archipelago in the hope of finding there, by means of important excavations about to be undertaken, the famous Missing Link theoretically foreseen, the existence of which should antedate Quaternary times. Certain hypotheses even considered the "Iles de la Sonde" as a possible cradle of the human race. Mr. Dubois, then, was guided by theoretic views; and if he has been fortunate in his research he has merited it by his competence as geologist and anatomist, also by the talent with which he has known how to turn his discovery to account.

It is all very well to find an inscription, it is another thing to decipher it. This latter task, as will be seen farther on, presented great difficulties which Mr. Dubois has overcome in a most creditable manner.

A very incomplete skull, two molar teeth picked up at a meter's distance from the skull, and a femur lying at some fifteen meters' distance, the whole enveloped in an earthy gang, very hard, and occurring in a bed which included other remains of a Pleistocene fauna to day for the most part extinct—such are the pieces of a more or less human appearance of which the specific determination was in question. It is obvious that the inscription to be deciphered is far from being perfect; the letters remaining are few. But these are the initials, and in the connection in which they are found, chance has served science almost as well as a judicious choice among all the parts of the skeleton could have done.

The two molars represent, in reality, in addition to the maxillary bones and the face, the vegetative function; the femur represents the function of locomotion; what is left of the skull suffices to give important indications as to the cerebral and intellectual development.

Although these different pieces were found separated a certain distance one from the other, the conditions of the deposit and the circumstances of the excavations have convinced Mr. Dubois that they belonged to one and the same individual. He has made a thorough and very careful study of them,^[2] of which the conclusion is that they attest the existence, in the Pleistocene epoch, of an anthropoid species of biped intermediate between the known anthropoids and the human species, precursor of the latter and probably descended from the genus Hylobates (Gibbon). In consequence, the new species received the name of Pithecanthropus erectus.

Strongly supported as they were, these conclusions were destined to move more or less, not only the specialists in zoology, anthropology, and paleontology, but also the entire thinking world. Appearing toward the end of the year 1894, Mr. Dubois' memoir was not slow in provoking criticisms and discussions, the history of which is not without some interest.

January 3, 1895, I communicated to the Paris Society of Anthropology^[3] a detailed estimate, based upon the study of the drawings, photogravures and tables, contained in Mr. Dubois' paper, and which, in part favorable to the conclusions of the author, may be summed up as follows:

It is not certain that the specimens in question belonged to the same individual nor even to a single species, but it is possible, for there is no lack of anatomical correlation among the different pieces.

The femur, for the human species and according to my tables for the reconstitution of the stature^[4] would correspond to a height of about l⋅657^m. This femur, by its pilastric index^[5] or index of a transverse section at the middle point of the diaphysis, indicates certainly a biped attitude. But it does not present a single character permitting one to attribute it to any other species than the human. Yet that invalidates in no way the general conclusion of Mr. Dubois, because on the hypothesis, where an anthropoid race would have passed from the attitude of a climber to the attitude biped, the transformation of the femur ought to have preceded that of the skull.

The tooth (3d upper molar) is too large sized, its roots too divergent to admit of its being attributed to man. I have been able to find only one human tooth (in a New Caledonian skull) which presents at once so large a crown and of which the principal axis is at the same time directed from before backward, but this is a third lower molar and its roots are not spreading. On the other hand, the grinding surface of the fossil tooth from Java differs much from the known teeth of anthropoids. It should then be considered as having belonged either to an anthropoid race, or to a human, no longer living.

The skull, according to Mr. Dubois' calculations confirmed by my own, has a capacity of from 900 to 1000^cc. This capacity exceeds by about 400^cc the maximum found among the largest anthropoids. On the other hand, it is too small to be compatible with a normal human intelligence, save among individuals of very small stature having a cranial capacity relatively large with reference to their stature and with reference to the average of their race. But, even discarding the teeth and femur about which there is some doubt, the morphologic characters of the cranium from Java suffice to denote a cerebral volume relatively very weak. The skull then must have belonged either to a normal individual of a race intermediate between the grand anthropoids and man, or to an abnormal man, to an imbecile, microcephalous for his race. This last supposition has the disadvantage of admitting the extraordinary encounter of an anomaly; if such an encounter is, strictly speaking, possible, it is hardly probable. In short, at least, a skull morphologically intermediate is in question. It is not certain that this skull represents the normal state of a fossil human race equally intermediate, but it is still less certain that it is a question of a simple anomaly. Consequently, the hypothesis of Mr. Dubois is scientifically legitimate.

 

Such were my first conclusions in January, 1895. But very different conclusions were reached at about the same time in Germany and in England.

At the Berlin Society of Anthropology,^[6] the question was examined by Kraüse, Waldeyer, Virchow, Luschan, and Nehring. There, the femur was declared human and the skull attributed more or less affirmatively to an anthropoid.

On the other hand, Cunningham at Dublin and Sir W. Turner at Edinburgh pronounced both skull and femur human; Rudolph Martin^[7] of the Zürich Univerity was of the same mind.

Such a divergence of opinions expressed by these anatomists, all of them so competent, would almost suffice to demonstrate the really intermediate state of the skull from Java, for it is well known how great the difference is between a human skull and that of a monkey. To give occasion for opinions so opposed, it was necessary that the skull from Java should present important characters human and important characters simian.

That which explains also the divergence in question, is that the human skull drops now and then to a simian level among the microcephalous of all races, and to a level approaching the Pithecanthropus among certain inferior individuals, especially in the lowest savage races.

1

Fig. 1 (fig. 53).—Profile of the cranial cap of Trinil; b, Approximate position of the basion; n, Rudiment of the temporo-occipital crest.

The skull from Java is no less remarkable in its general form than in its weak capacity. Its entire median curve is extremely elliptic; the forehead is extremely narrow and tapering. The lower portion of the frontal bone above the orbits forms a sort of visor of which the relative prominence surpasses all known proportions in the human species, not excepting, even, the famous Neanderthal skull. The lateral projection of this visor is not less extraordinary and denotes a great depth of the temporal fosses. The frontal region presents a lateral flattening which gives to the ensemble of the cranium a pyriform aspect when seen from above. The posterior parietal region is flat from above downward to a degree no less remarkable. The occipital crest is very thick. The temporal crests do not come very near to the sagittal suture, but they are pro- longed downward and backward in such a way as to form a parietal super-mastoid crest which goes almost to form a junction with the occipital crest. I at first pointed out with some reserve this simian character after a photogravure in Mr. Dubois' memoir; but I am now no longer in doubt as to its reality. Finally the foramen magnum and the auditory meatus, which are missing, appear to have been situated a little farther back than in the human species.

As has been said above, human crania very inferior for their race sometimes approach more or less in volume and form to anthropoid crania. Professor Turner^[8] has also been able to show many exceptional human skulls that approach to a remarkable extent the skull from Java with reference to capacity, etc. But, if we suppose that collections of crania richer than those that we possess would permit us to find upon human crania all the characters of inferiority noticed on the Pithecanthropus and to a degree as pronounced, the skull from Java would present none the less this peculiarity: that it brings together a group of characters all of them the limit for the human race. It is the union of these characters that it behooves us to consider, all the more so that the coexistence of certain of these characters on the same skull is particularly interesting. Thus normal human crania can have an inferior capacity of 1000 cubic centimeters, but then these are pigmy crania, and they come up again with respect to the general form because they contain a brain relatively voluminous with reference to the stature; they have no right, so to speak, to that enormous frontal visor which is, among all races, the lot of individuals with powerful skeleton and brain relatively small, or of averred microcephalous individuals whose development of skeleton approaches the medium.

Besides, let us admit that a non-pathological human skull may be found in which are united all the "caractères limites" of the skull from Java; that would prove nothing against the hypothesis of Mr. Dubois, for such a skull would be always a very rare exception in any human race whatsoever, whereas, according to all probability, the one skull found in Java is not a rare exception in its race. And then this race is of the Pleistocene epoch, which of itself would give no ground for astonishment were its one known specimen morphologically inferior to our present races. We will refer further on to this question.

The opinion expressed in Germany is explicable, in the first place, by the fact that they commenced by attributing the femur of Java to a man without further question. In the second place, they emphasized too much the simian characters of the cranium and teeth. They saw that, according to these characters, the race of Java could not be attributed to the human species, but forgot that, according to other characters, they had no right to attribute it to the race of monkeys. For no known anthropoid approaches the fossil race of Trinil either by its cranial capacity or by its occipital characters at an adult age.

Besides, a view of the remains themselves and a more thorough study of them have already resulted, so it seems, in a change of the opinions first expressed.

Be that as it may, Mr. Dubois can congratulate himself on seeing placed in relief, at Berlin, the reasons according to which his Pithecanthropus could not be a man and, in England, much better reasons according to which the same Pithecanthropus could not be a monkey.

The question rested there until the International Zoölogical Congress was held in Leyden, September, 1895. At this congress, where were found such eminent zoölogists and anatomists as Sir W. H. Flower of London, A. Milne Edwards, Perrier and Filhol of Paris, and others, Mr. Dubois showed the fossil pieces from Trinil, to which was added another tooth (2d molar) which he mistook at first, before having completely cleared it from its matrix, for a tooth of Suidæ. The view of the originals did not result in calling forth decided affirmations from the Congress. According to the information that I received from Mr. Dubois and from Professor Kollmann of Bâle, and according to a communication made to the Paris Academy of Sciences by Milne Edwards, the question was considered as demanding further research. Professor Virchow, without committing himself, emphasized certain pithecoid characters of the skull and femur, notably the resemblance of the femur to that of the gibbon; he showed especially that, according to researches made in the collections of Pathological Anatomy of Berlin, the voluminous osseous vegetation presented by the femur of Trinil in the posterior sub-trochanterian region might be due to an abscess from congestion of the thigh, probably following a caries vertebral.

Mr. Dubois having satisfied himself, at Leyden, that the direct view of the fossil remains from Java contributed much to corroborate his demonstrations, kindly took those remains first to Brussels, then to Paris, then to Dublin, to Edinburgh, London, Berlin and Jena. He will set forth, without doubt, in the near future the happy effects of that scientific tour upon anatomists when he describes the fossil fauna (Upper Pliocene) contemporaneous with the Pithecanthropus. The opinion adopted seems to be to-day very generally analogous to the one set forth at the beginning of this article.

2.

Fig. 2 (fig. 54).—Norma verticalis of the skull of Trinil compared with that of the Neanderthal skull.

It is the aspect of the specimens from Trinil and their complete fossilization, which surpasses by far that of all human remains, even the most ancient known until then, that tend more powerfully than all demonstration to place them as contemporaneous and as coming from one and the same individual, especially since there exists among them no want of anatomic correlation. The degree of fossilization is such that the femur attains the weight of 1 kilogram, whereas prehistoric femurs of the same size do not exceed 350 grains. All that, joined to the conditions of the deposit, adds value to the divers anatomic facts and deductions given above, and constitutes a mass of arguments before which it becomes difficult not to surrender. Without doubt, these diverse fossil pieces, which all present characters intermediate between the human and the simian morphology, these diverse portions of the skeleton which are all explained the one by the other, do not come from two or three different species which would have met in some way by special appointment within a space of a few meters to leave there, one its skull, another two teeth, and a third its femur, the whole without want of correlation.

As regards the femur, I have studied particularly the character upon which Mr. Dubois insists, viz: the almost cylindrical form of this bone in the poplitic region, 4 centimeters above the upper margin of the condyles. At this level, the transverse diameter is ordinarily much greater than the antero-posterior diameter. On the femur of Trinil these two diameters are almost equal. At the same time, if we measure, beginning at a point anterior m, two antero-posterior diameters, the one ending at the median point p, the other at the point n situated on the external branch of the bifurcation of the linea aspera, we find mn < mp. I have been able to find this double character on only six human femurs out of more than a thousand belonging to races very diverse. Again it is less accentuated than on the femur from Java, so that this femur presents also in this respect a new "caractère limite" for the human species. One human femur alone presented this character to the same degree as the femur of Trinil; it is a Parisian femur of the Middle Ages, and this bone is pathologic; it presents grave coxalgic lesions and divers characters attesting a consecutive functional impotence. A detailed interpretation of the character in question is found in the Bulletin de la Société d' Anthropologie (t. vi, 4^me sér.). It can be summed up as follows:

3.

Fig. 3 (fig. 55).—Transverse section of the femur 4 centimeters from the upper margin of the condyles.—Scheme representing the passage from the common type 1 to the form of the femur of Trinil 6.—EI, Transverse axis.—Ap, Antero-posterior axis.

This character can be produced sporadically in any race whatsoever; it does not seem to possess any ethnic value in the human species, it seems to be connected most often with a certain muscular weakness and can be the result of a lesion affecting the upper part of the bone. As the femur of Trinil presents exactly such a lesion, resulting itself from a malady capable of entailing during a period of years a relative impotence of the lower members, it is quite possible and, I believe, even probable that if we should find a second femur from the same race, it would be very different from the one we possess.

This has none the less a very great importance, because it attests peremptorily the "marche bipède" which the cranial characters had been powerless to demonstrate in a sufficient manner, and the rather large size of the subject. It is sufficient for us to know that the femur of Trinil is not that of a monkey but that of an animal maintaining the upright position, an idea which is not in the least disturbed by pathologic considerations. If the femur in question had been completely sound, its form would have approached even more the ordinary human form. Such as it is, it does not recall, in my opinion, the femoral form of the gibbon any more than the Quaternary femur of Spy, described by Mr. Fraipont, recalls the femoral form of the gorilla, provided one does not take into consideration the characters connected with an upright position. In other words, the femur of Spy, although human, would not be less pithecoid than that of Java.

Mr. Hepburn^[9] of Edinburgh does not regards the characters of the femur of Trinil as sufficiently pronounced to form a genus distinct from the genus Homo. These characters are human and not simian. Upon this point, we are in accord. He adds that if the femur comes from a human being, and if the teeth and skull belong to the same, then the conclusion relative to the femur should apply also to the skull and the teeth.

On this last point, the justice of the conclusion depends on the signification attached to the term human being. If the femur of Trinil, considered separately, proves that its possessor was not a monkey, it certainly does not prove that its possessor ought to be classed according to the totality of its conformation in the human species, or genus, so far as known. I have already insisted at length upon this fact, that the femur can be morphologically very human in a being low enough with respect to cranial development to merit only conventionally the name of man. It is necessary, then, to take into account its skull and its teeth, as well as its femur, in an estimation of the fossil individual from Trinil. According to the femur, it would be a man with a perfect title to the name ; according to the skull and the teeth, it is a creature low enough, in relation to the lowest human races, to be considered as passing beyond the lower limit for the human species or genus, so far as known, in the measure that its inferiority represents the inferiority of its race. It is this last point that rests in the condition of a hypothesis, but of a hypothesis which has for itself the greatest possibility. This hypothesis admitted, we are obliged to agree, viewed from the point of view of the theory of evolution, that the individual of Trinil, incontestably hominian, presents an ensemble of anatomic conditions responding marvelously to that which the theory of evolution could look for in an ancestral race.

4.

Fig. 4 (fig. 56).—Attempt at the reconstruction of the skull of Pithecanthropus.—B, Basion. The points marked about the letter B indicate the limit of possible errors.—C, Occipital crest.—pt, Inferior parietal crest almost joining the occipital crest.—i, Inion.—HH′, Horizontal plane of Broca (alveolo-condylian).—BA, Basio-auricular line.—BO, Plane of the foramen magnum.

As regards the skull, I have been able, by virtue of the cast kindly given to the Anthropological Laboratory by Mr. Dubois, to attempt the graphic reconstruction. I made the attempt simply to satisfy myself of the aspect resulting from diverse craniologic proportions, but I believe I have obtained a drawing conforming approximately enough to the reality to be of interest to anatomists.

5.

Fig. 5 (fig. 57).—Skull from Turkestan of bestial aspect in which is inscribed, by means of a dotted line, the cranial cap of Trinil.—IF, Inio-orbital line common to the two skulls.—T, Curved temporal line of the skull of Turkestan. This skull is extremely remarkable for the extent of the surface of insertion of the temporal muscle. It presents the crest pt of figure 4 (56). The sincipital region is mutilated by a sabre stroke.

 

6.

Fig. 6 (fig. 58).—Skull of a young chimpanzee.

The maximum error possible for the separate points of the skull has been limited by correlations so diverse and rigorous that the errors which could have been committed cannot modify them, notably the general form of the skull, properly speaking,, and its orientation. The figure thus obtained seems to me to make it evident that, it is impossible, with the cranial cap of Trinil, to construct a skull having an appearance either completely human or completely simian. The occipital characters which I attributed to it differ radically from those of adult anthropoids; in vain did I orient it in superposing it upon a human cranium; it had not, for that, an appearance suitably human, and we attempt in vain to pivot it about its bi-auricular axis in order to give it an air more human or more simian : we are struck by divers incompatibilities. The truth, which, I think, will appear clearly to all craniologists, is that the skull from Trinil represents the morphologic stage of the young anthropoid, a stage during which these animals approach man in important cranial characters much more nearly than at the adult age.

7.

Fig. 7 (fig. 59).—Skull of Margaretha Moehler, microcephalous adult of Carl Vogt. The dotted lines represent two well developed feminine crania from Paris; one large, the other small. The auditory meatus is the point of superposition.

The adult Pithecanthropus possessed these characters of the young anthropoid; such is the result of our attempt at reconstitution, result independent, I repeat, of incurring chances of error, independent also of any preconceived idea, for I have striven only to place each separate point of the cranium and each line conformably to anatomic correlations without preoccupying myself as to the final result. It has been admitted that the two molars, the femur, and the skull belong to the same individual, but this hypothesis has not exercised the least influence upon the drawing of the cranial region, properly so called. The technical details and justifications are to be found in the Bulletin de la Société d' Anthropologie above mentioned. I present here only a few drawings, which may be compared advantageously with the preceding.

The fact that the skull from Java bears such a strong morphological resemblance to that of a young anthropoid is of a nature to explain the divergence of opinions, some of which ascribe it to a monkey, others, to the human species. But as it is a question of an adult, this fact is pronouncedly in favor of ascribing the skull to the human species with the reserve that it occupies a rank morphologically intermediate between anthropoids and the lowest human races. However, an anthropoid maintaining the upright position and possessing such a cranium is nothing less than a low order of human, for it has lost the essential traits which differentiate man from anthropoids. It is understood in this sense that the opinions of Turner and Cunningham do not differ from mine.

The important thing is the establishing of the fact that the craniologic inferiority of fossil human races, according to the specimens we know, increases with their antiquity. The discovery of Mr. Dubois contributes to establish this fact.

Let us represent by a line AD the entire family of Hominidæ, which, for the theory of evolution, includes, in addition to the genus Homo in its known state CD, an unknown fossil portion CA, connecting the known portion with an anthropoid ancestor whatsoever A. When we say that the individual from Trinil belongs to the human species, that signifies that it can enter into the portion CD within the limit L, which, for the anti-evolutionists, the human species must not overlap.

When it is said, on the contrary, that the race of Trinil is inferior to all known human races including the portion C, it is considered thereby even as one of those intermediate races TT' which, according to the theory of evolution, ought to have formed the unknown portion of the line AD.—Whether or not we place this race under the genus Homo (which is of little moment for the evolutionist), we consider it as one of the intermediate fossils theoretically foreseen. To contradict this opinion and to attach the man of Trinil to the race of Spy is to admit that it is a question always of the portion CD representing without theory the species or genus Homo. Such was the former opinion of Turner and of Cunningham; opinion which has been perhaps modified since the direct examination of the specimens under discussion.

According to the contrary opinion, the Pithecanthropus represents one of those fossil human races that the theory foresaw, for it is morphologically intermediate, by its skull, between the lowest human races and the anthropoid type. A partisan of the theory of evolution has no repugnance to considering that race as human and to saying "the man of Trinil," since, according to the theory, the chain AD is necessarily uninterrupted. Whatever be the names that we shall judge proper to give to the divers links of this chain, it will be a question always of man more or less inferior as far as the point where, the type of "bipède marcheur" disappearing, we shall emerge from the definite family of Hominidæ to enter into another branch of the genealogic tree of Man.

If it is preferred to settle the question by saying that the skull of Trinil simply puts back the limit L beyond its present position, just as the skulls of Spy have extended this limit as regards the races of Europe: from what I have just said I should not see the slightest objection to that, since it seems to me this limit L is destined to be put back by successive degrees as far as to the level A.

Theoretically it is highly probable that an anthropomorphous species, evolving toward the human type, ought to have realized at first in the adult state the characters of superiority that it possessed transitorily in the young state before that evolution. The disappearance of these infantile characters of superiority results, as I have shown in a former memoir,^[10] from the precocious arrest of development in the cerebral mantel, when the central and inferior encephalic region as well as the basilar region of the skull continue to grow, keeping pace with the general development of the body. The Pithecanthropus would represent then that inferior phase of human evolution in which the intellectual and cerebral improvement would have been just enough so that the development of the upper portion of the skull would not be left in arrears any more than it is in the young anthropoid compared to the basilar development correlative to the corporeal growth in general. Among the lowest existing human races, this stage of evolution is largely exceeded for the normal individual. The difference is yet greater for the average among European races.

At any rate, the quality of precursor attributed by Mr. Dubois to his Pithecanthropus reposes upon an ensemble of facts of consequence enough to merit the most serious attention. In addition, behind this hypothesis there arises another to the view of the evolutionist. It is quite natural to propose the question whether the precursor were not something more, that is to say an immediate ancestor of man or of a part of the human species.

The hypothesis of a simple precursor can be accepted without repugnance independent of the doctrine of evolution. It simply places an intermediate species between anthropoid and man and confirms once more the adage: Natura non faeit saltus. It reduces itself to a simple verification. In favor of this hypothesis there will be, on the one hand, all the arguments produced to demonstrate that it is a question of the anthropoid species, but veritably simian, until then unknown; and on the other hand, all the arguments produced to demonstrate that it is a question of the human species.

The hypothesis of a veritable ancestor will profit by all these arguments, for all will tend to establish the existence of an uninterrupted chain. In insisting upon the simian characters we strengthen, voluntarily or not, the affiliation of the Pithecanthropus with monkeys; in insisting upon the human characters, we render more probable the affiliation of the intermediate species with the human.

The scientific event due to the laborious researches of Mr. Eugene Dubois is of a nature to give joy to all friends of science, but it seems to be more particularly agreeable to evolutionists, that is to say, to those who desire and pretend to explain why natura non facit saltus. For these last, the question whether the Pithecanthropus ought to be classed with the genus Homo sapiens depends upon the value attached to the qualifying word sapiens, the value of which is already very relative. As to the question of species it is, for the evolutionist, like the preceding, a simple question of degree of morphologic differentiation.

It is none the less interesting to search for the particular simian genus to which would fall the honor of becoming founder of the human branch, in other words the known anthropoid genus to which is allied the intermediate Pithecanthropus.

Mr. Dubois has thought of the genus Hylobates (Gibbon) and the general opinion at present seems to accord with this view. All the appearances are in its favor, because of the relatively grand analogies which exist between the conformation of the gibbon and that of man.^[11]

The almost vertical attitude of the Gibbon corresponds to the very marked anatomic particularities which would render easy the human transformation. The conditions of this transformation, that is to say of the passage from the state of climber to that of "marcheur bipède," ought to have been very imperious, for it is difficult to believe that, without that, a race of climbers took spontaneously the initiative in renouncing a mode of locomotion in harmony with an adaptation instinctively and organically fixed.

One hypothesis among others would be the destruction, more or less complete, of the forests on an island inhabited by anthropoids capable of taking, when necessary, the biped attitude. The ancient volcanoes of Java might have accomplished this destruction and have rendered necessary the adaptation to the upright position under pain of extinction of the race.

It would be impossible to explain easily the disappearance of an anthropomorphous species as much superior to all others as was that of the individual from Trinil; for it was strongly built with a cerebrum superior to all known species of the order of Primates. It possessed, then, excellent chances of survival in the struggle for life. But, on the hypothesis here considered, the species Pithecanthropus erectus would not have disappeared. Having become a human race, it could not remain at the same time a race anthropoid. If the Pithecanthropus was only a simple precursor, it was superior enough to the other animals to survive unless the human species, springing up all of a sudden, "from the clay of the earth," did not hasten to annihilate this dangerous competitor. But if the Pithecanthropus was an ancestor, its species lives yet in its human descendants.

The difference between the Pithecanthropus and existing man is so small that there is no call to search for an intermediate link. The link is sufficiently represented by the lowest of our savage races; for example, the isolated human skulls, Australian and others, that have already been shown to be very little different in many respects from that of Trinil.

Supposing that among several species of gibbon, Gx, Gy, Gz; this latter species evolved toward the human type and became finally, in assuming the upright position, the Pithecanthropus erectus=H¹, then that it, by virtue of the multiple consequences of the upright position, became progressively H², a stage corresponding to the lowest existing races, we obtain in simplifying:

Gibbon x
Gibbon y
Gibbon z—H⁰—(P.E.=H¹)—H².

There ought to be then in the existing fauna a hiatus formed by the transformation of the gibbon z into H⁰, then of H⁰ into H¹, so that, in this existing fauna, the species nearest to H² ought to be a species very inferior, issue of gibbon x or y. The gap here ought to be all the greater in that it is not only a question of a transformation such as that of one quadruped into another, conserving the generic characters of its ancestor; but of a transformation of the attitude even, that is to say of morphologic conditions entailing a radical change of type and, indirectly, of physio-psychologic modifications very profound.

The existence of a hiatus between two related living species cannot then serve as argument against the theory of evolution. This hiatus, as we have just seen, may be, on the contrary, a direct result of the transformation of one species into another.

Although the transformation here supposed has been very profound, enough so to give birth to a pretended new kingdom, "human kingdom," that transformation could have been produced, according to the above hypothesis, without compelling Nature to make, in any sense, a leap. It may be possible, from a point of view purely zoötaxic, to establish a veritable saltus, but I have just shown that this saltus could have been the gradual consequence of a simple modification of habits of locomotion in a race of monkeys already capable of assuming the upright position. The motive for this change could have arisen abruptly, but there has been no anatomic leap from Gibbon z to existing man. That which can have been produced abruptly is the exterior condition from which would have resulted, for an anthropoid race of climbers, the necessity of adopting habitually a mode of locomotion which it was already capable of utilizing occasionally. The only thing abrupt, from a biologic point of view, would have been a simple increase in the frequency of the utilization of a functional aptitude already existing. Multiple and considerable anatomic modification may have been entailed by this change of the habitual attitude, but they ought to have been produced by insensible degrees and are all the less astonishing in that the anthropoids already approach much nearer to man than to monkeys proper in their general conformation (Huxley, Broca).

If there is a gap between the existing human species and the precursor, the fossil remains of the intermediate races ought none the less to exist. There ought to be the remains of H⁰, of gibbon z and of Prothylobates. Will these last perhaps reveal a species remarkable in stature and in a relatively superior aptitude for the upright position? That is not necessary theoretically: the diverse species of the genus Hylobates have a conformation which enables them to assume the upright position with ease; the form may have undergone considerable variations after the transformation of the attitude.

Finally, it is probable that the species gibbon z approached man in certain respects more than do known species of the genus Hylobates.

However, if we admit that the pieces found at Trinil really represent the remains of a Pithecanthropus, and if it is admitted that this was an ancestor of man, it is necessary to find now an ancestor to this Pithecanthropus, and it seems requisite that this ancestor be not inferior to existing anthropoids. It must have been capable of adopting, in case of need, the upright position, and been led, by its conformation, to take that attitude rather than the quadruped attitude. Such would be certainly the case with all known anthropoids, all of which are veritable biped climbers.

Let us recall here the existence in the Miocene epoch of several anthropoid species such as the Dryopithecus, the Pliopithecus, and the Anthropopithecus sivalensis. As Mr. Dubois has remarked, his species does not lack for ancestry.

The transformation of the habitual mode of locomotion may have been very rapid, but the consecutive, morphologic transformations must have demanded much time and cannot have been fixed hereditarily until after a certain number of generations—hundreds perhaps, and perhaps many less, for selection under the conditions indicated above may have been very active; the two sexes must have contributed actively to the progression, and the young must have imitated their parents with an ever-increasing facility. As regards the direct morphologic consequences of the change of attitude, we may suppose they were produced with great rapidity, if we are to judge from the multiple skeletal variations caused in man under the influence of the minimum of functional variations compared with those with which we have to do here.

As regards cerebral increase, it proceeds with such slowness that we can scarcely affirm the fact has been established at all for our European races since prehistoric times. But the cranial capacity of the Pithecanthropus surpassed by about 300 grams that of the largest gorillas. It surpassed by at least as much that of its ancestor gibbon z, if this latter was of the same stature as the Pithecanthropus. There is here an enormous difference, greater than that between the average for our lowest and the average for our highest existing human races. It is not, however, embarrassing for the hypothesis under discussion.

We must consider, in fact, that the human species has never realized, since the beginning of its existence, a progress comparable to that represented by the passage from the state of climber to the state of "marcheur bipède." This passage represents a veritable liberation of the superior members, the hands, previously employed as organs of locomotion the same as the feet. It is by the mode of locomotion of the climber that the hand became, little by little, apt for the function of prehension, then for the function of manipulation, and it is by virtue of the complete emancipation here supposed of the superior member with reference to locomotion that the functions of prehension and of manipulation of the hand have been able to acquire adaptations the most varied. The perfecting of the tactile sense must have been an immediate result of this emancipation. This result must have involved the acquisition of a multitude of new notions suggesting new movements, new actions. From that, the multiplication of the movements of the lingers and of their combinations, the increase in manual skill and all the psychologic consequences, reacting the one upon the other, which must have been produced necessarily, by increase, in variety and complexity, of newly acquired motive and sensorial representations. On this subject, I could not do better than to refer the reader to the beautiful pages devoted by Herbert Spencer to the parallelism of the sensorial and motor improvement in the animal series together with the intellectual improvement.^[12]

It is impossible to say, even approximately, to what augmentation of cerebral weight the transformation in question may correspond, but there are grounds for believing that this augmentation must have been considerable, all the more so since the intellectual growth in question must have influenced simultaneously the sensorial and motive manifestations, and the order of sensations the psychologic importance of which is extreme, and the order of movements (the movements of the fingers) very numerous and which we know to be of great help in the function of expression. This function is perhaps the most important to be considered here, because its progress reacts in a capital manner upon intellectual and social development. It may have been noticed, among divers savage peoples, how much the language by gesture makes up for the imperfections of the spoken language; it is then allowable to suppose that the movements of the hands and of the fingers figured largely among the primitive means of expression of Pliocene man.

I do not believe it is possible to cite any ulterior cause of psychologic progress and of increase in brain weight comparable to the emancipation of the superior members with which . we have just been occupied. The perfecting of articulate language must have been consequently the principal factor supervening in the psychologic and cerebral progress, to which would be due the superiority of the lowest existing races over the Pithecanthropus.

The quantitative cerebral progression has been accompanied by an improvement in the general form of the brain. This improvement is already perceptible in the Pithecanthropus according to the general form of the skull; it seems, however, to have been about parallel to the quantitative progress from the anthropoid precursor to civilized man. But it is not possible to introduce here this very complex question with the necessary developments.

It would not be absurd to try upon the gibbon an experiment conformable to our hypotheses. Without going so far as to wish to reproduce the formation of a new Pithecanthropus, we might attempt to picture what would happen to the attitude in placing the gibbon under conditions favorable to the transformation of its habits of locomotion.

As an intermediate form between man and monkeys, it is difficult to image anything more satisfactory than the skull of Trinil. If this skull, as is probable, is not exceptional for its race, we can count upon finding other specimens approaching still more nearly, either to man or to the monkey. But what the race of Trinil has not yet furnished, have not the lowest human races furnished in abundance? Do there not exist human crania, inferior compared with the average of their race, which show to us all the transitions theoretically desirable between man and the Pithecanthropus? All the inferior human crania which it would be possible to show as approaching the form of Trinil by certain characters would make up very well for the absence of the better specimens of the race Pithecanthropus. But it will be difficult to find, among normal human skulls, specimens as pithecoid as that of Trinil. We see frequently in a race such and such individual characters recalling an ancestral type, for it is easier to descend than to ascend in matters of evolution; but the pathologic arrests of development supervening during the embryonic stage only are capable of giving rise to a whole ensemble of characters recalling a remote phase of phylogenic evolution. Microcephalous idiots only, even among the lowest human races, present such an ensemble of characters which come to realize a morphologic type inferior to that of Pithecanthropus itself.

The distance existing between the Pithecanthropus and normal man must be considered as a necessary result from the point of view of evolution. It is the superior portion of the intermediate race which can have survived and formed an inferior human race. This latter must then present characters superior to the average of its ancestors, even independently of the progress that this human race can have realized since the Pliocene epoch. The existence of human crania presenting at once the ensemble of the cranial characters of Pithecanthropus has not yet been demonstrated, unless we take into account the microcephaly more or less accentuated, that is to say, a veritable anomaly by arrest of development. But we cannot represent a race by an abnormal skull, and it will be noted in the present instance that the resemblance existing between human skulls more or less affected by microcephaly and the skull of Trinil would not contradict the hypothesis according to which this last would represent an ancestral race. This resemblance, on the contrary, would be perfectly conformable to the theory of evolution, and it exists. Without going beyond civilized races, we know that complete microcephaly carries man back to a level with the monkeys. It is then solely the poverty of our collections which has kept us from finding, among the lowest human races, skulls as pithecoid as that of Trinil. The skulls presented by Sir W. Turner, in his interesting memoir on the subject, approach it only partially. It is the same with the Sambaqui skull which Professor A. Nehring of Berlin has just confronted with that of Trinil.^[13]

Crania approaching more nearly to that from Trinil under the double aspect of form and of capacity will certainly be found, but they will be crania very inferior to the average of their race; they will be the microcephalous, the abnormals.

Nothing would better serve to show that the species of Pithecanthropus and the human species penetrate into each other and are mutually bound together. The bond would be still more complete if we should find some day, by virtue of inverse operation, a whole fossil series of the race Pithecanthropus erectus, of which the superior extremity would accord morphologically with the average of our lowest races.

To invalidate the legitimate and probable hypothesis of Mr. Dubois, it would be necessary to show that the skull of Trinil is a simple monstrosity without ethnologic signification. This chance would be mathematically possible, since the race of Trinil must have had, as others, its microcephalous individuals; and it is for that reason that the opinion opposed to that of Mr. Dubois can pride itself, until there has been further investigation, in one possibility as against thousands of contrary possibilities. The improbability of a case of submicrocephaly coincident with a stature at least medium seems to me still greater since I have seen the two molars of Trinil, for teeth too large and too long for a normally developed savage would attest, in case of human microcephaly, one more singularity; a microcephaly which would have exaggerated, not only the volume of the teeth with reference to the skull, but also the absolute volume of the teeth beyond the ethnic maximum.

The hypothesis of a case of microcephaly being cast aside, two others remain.

1st. During the Pliocene epoch, there lived in Java a human race intermediate between the lowest of known races and anthropoids.

2d. During the Pliocene epoch, there lived in Java an anthropoid race possessing the "marche bipède," and intermediate, in cerebral development, between the highest forms of known monkeys and the human species.

We may fuse these two hypotheses into one, from the point of view of the theory of evolution, that is to say, we may consider with great probability the race in question not only as a race precursor for the human species, but also as a race ancestral, as the commencement of humanity.

That there is in all this much hypothesis, I do not deny. But the attributing of the pieces from Trinil to two or three unknown species closely resembling man, or to a single abnormal specimen of the human species, that is, also, merely hypothesis.

Then, since we are obliged to have recourse, in any case, to a hypothesis, we have to ask which one is the most suitable, not only to explain the facts directly on trial, but also to clear up this question henceforth thrust imperiously before us for examination, namely, what can have been the human species during the Pliocene and how can it have originated? In the presence of the discovery of Mr. Dubois, it is advisable to examine the question in its entirety.

The question does not admit of a mathematical demonstration, but there can be a degree of probability great enough to carry with it conviction. To admit as true, until there is proof to the contrary, a hypothesis which answers to a great number of facts without being contradicted by any, is to act in accordance with the scientific spirit. It has often been said that science does not consist in a heap, but in a chain, of facts. To discover this chain, hypothesis plays a necessary role. Certain zoologists suppose that the human species has had no ancestors. If this hypothesis, of which the probability is not of the first order, seems to them to be scientific and fruitful, the opposite hypothesis can boast of titles to belief at least equal, in our opinion. And if the human species did not appear by spontaneous generation,—if, on the other hand, the cranial characters of Quaternary man found in Europe represented a phase of evolution very little removed from the existing phase, there is cause for believing that there would be found in Pliocene deposits a race morphologically inferior to that of Neanderthal and of Spy. But this is precisely what has happened. The anthropomorphous human race, if you choose to call it so, found by Mr. Dubois, presents characters such that it may have resulted directly and progressively from the transformation of a race of anthropoid climbers. Under these conditions, if the doubt on the subject of the simian origin of Man is only proportionate to the reasons of a scientific order capable of giving rise to it, it seems to me it must be a very slender doubt.

1. Two illustrated papers on the Pithecanthropus erectus have already appeared in this Journal, both by Professor O. C. Marsh, who from the first regarded this new form as intermediate between man and the higher apes. See vol. xlix, p. 144, February, 1895; and vol. i, p. 475, June, 1896.—Ed.
2. Pithecanthropus erectus, eine menschenæhnliche Uebergangsform aus Java (Batavia Landesdruckerei, 1894).
3. Discussion du Pithec. erectus comme précurseur présumé de l'homme (Bull. Soc. d'Anthr., fasc. 1, 1895).
4. Mém. sur la détermin. de la taille d'après les grands os des membres (Mém. Soc. d'Anthr. de Paris, § 2, t. iv, 1892).
5. Étude sur les variations morph. du corps du fémur dans l'espece hum. (Bull. Soc. d'Anthr., 1893.)
6. Zeitschrift für Ethnologie, Heft i, 1895.
7. Kritische Bedenken gegen den Pith. erect, Dubois (Globus, Band lxvii, No. 14.)
8. Jour. of Anat. and Physiol., vol. xxiv, 424.
9. Journal of Anatomy and Physiology, vol. xxxi.
10. Sur les modif. du profil encéphalique et endocr. dans le passage à l'âge adulte, etc. (Bull. Soc. d'Anthr. de Bordeaux, T. 1, 1884).
11. Paul Broca: L'ordre des Primates (Bull. de la Soc. d'Anthr., T. iv, p. 228, 1869).
12. H. Spencer, Principles of Psychology, vol. i.
13. Ein Pithecanthropus-ähnlicher Menschenschädel, etc. (Naturwissenschaftliche Wochenschrift, 17, Nov. 1895.)