THE INTERORBITAL WIDTH. A NEW CRANIAL DIMENSION. ITS SIGNIFICANCE I N MODERN

AND FOSSIL MAN AND I N LOWER MAMMALS

JOHN CAMERON

CRBNIOMETRIC STUDIES, No. 28

When a keen observer has his first inspection of the negro crania in the Hamann Museum, there are at least two very striking features that arrest the attention, namely, their splendid dentitions and the remarkable width between their orbits. The latter condition is so outstanding that one is thereby enabled to locate at once the position of these negro crania on the shelves of the museum. Professor Wingate Todd suggested to the writer that he make a study of this dimension, with particular reference to the interorbital width of fossil man. The present paper is the outcome of this investigation.

The first problem that had to be solved was the selection of a point on each inner orbital wall that would be in every way suitable for the purpose of making this new cranial measurement. The chief qualifications for such a point nat- urally were that it would have to be readily localized and at the same time really represent as far as possible the point of maximum interorbital width. After some deliberation, Pro- fessor Todd and the writer decided to select Martin’s lachrymal point(4) as the one that most closely satisfied the above requirements. The definition of this in his book reads as follows: “derjenige Punkt an welchem die Crista lachrp- malis post., die die Tranengrube nach hinten begrenzt, mit der Sutura fronto-lachrymalis zusammentrifft. ” Put briefly, then, the lachrymal point is the junction of the upper end of the lachrymal crest with the frontal bone. I t may be noted

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that the distance between the right and left lachrymal points is usually the position of maximum interorbital width, when a skull is examined from the front. As a matter of fact, there may be points on the inner orbital walls situated farther back that are slightly more apart, but they are too indefinite and also too variable. Professor Todd and the author were satis- fied that the lachrymal point was the one that most con- veniently met all the necessary conditions. All the measure- ments were made by means of the short blades of the Swiss pattern of craniometer. All the Hamann Museum crania that were measured in this way had been previously sectioned mesially. After careful calculation, Professor Todd found that an average of 1 mm. had to be added to each measure- ment for the purposes of making up the loss of bone tissue incurred while the skull was being sectioned in the midline. The cranial material that was utilized in this research con- sisted of sixty Hamann Museum male white and sixty Hamann Museum male negro crania. The museum also possessed reconstructions of the Rhodesian, Gibraltar, La Chapelle, Galilee, and Talgai skulls, representing fossil man. He also utilized the crania of the three highest anthropoids, while the lemur group was represented by Tarsius. The writer wishes to thank Professor Todd for many valuable facilities and much kind help. He also expresses his best thanks to Doctor HrdliEka for the privilege of studying thirty male Greenland Eskimo crania, fifteen male Mongol crania, and five native Australian crania in the U. S. National Museum.

The interorbital width displayed the usual wide ranges of variation in the case of the Hamann Museum white and negro crania. It will be observed from table 1 that the highest maximum dimensions were found in the negro crania. On the other hand, the lowest minimum dimensions were found in the white and Eskimo crania. It was noteworthy that by f a r the smallest range was found in the Eskimo crania, as one would expect in a comparatively homogeneous race. The low maximum for the Eskimo crania was rather striking.

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TABLE 1 The interorbital width displays the usual wide ranges of variation except in a

comparatively homogeneous race like the Eskimo dfaximum, Afwaimum. Ranpc of variation,

mm. mm. mm.

Male negro (Hamann Museum), 33.3 20.2 13.1 Male Eskimo (U. S. Natl. Museum), 25.2 19.1 6.1

Male white (Hamann Museum), 29.5 18.5 11

The standard deviations and coefficients of variability of the interorbital width were calculated in the cases of the Hamann Museum white and negro crania and the Eskimo crania. They could not be estimated for the other cranial groups, as the numbers examined were, of course, too small. The standard deviation for the male white crania was 2.56, with a probable error of 50.1576, while the coefficient of vari- ability was 10.406, with a probable error of 20.6406. The standard deviation for the male negro was practically the same as that for the male whites, namely, 2.57. The probable error in this case was e0.1582. The coefficient of variability for this cranial group was estimated to be 9.46, with a prob- able error of 50.5824. The standard deviation for the male Eskimo crania was very low, namely, 1.701, with a probable error of 50.1481, while the coefficient of variability was 7.83, with a probable error of 50.48209.

T H E AVERAGE INTERORBITAL WIDTH I N MODERN M A N

The average interorbital width for the Hamann Museum male white crania was ascertained to be 24.6 mm., with a probable error of k0.2229. On the other hand, it was found to be definitely greater in the male negro crania, namely, 27.15 mm., with a probable mean error of k0.2237. There was thus a marked racial difference, more particularly when one considered the smallness of the cranial dimension that was being dealt with. Indeed, when one reduced this racial difference to a percentage basis, it was calculated that the average dimension in these male negroes represented an increase of as much as 9.3 per cent, when compared with the corresponding dimension for the male white crania.

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The Hamann Museum female crania confirmed the above results. For instance, the average interorbital width for sixty female white crania proved to be 23.3 mm., whereas the average for sixty female uegro crania was again definitely greater, the actual figure being 25.5 mm. The average dimen- sion in these female negroes represented an increase of 8.6 per cent, when compared with the corresponding dimension for the female white crania. It was thus evident that this new cranial dimension exhibited a well-defined racial difference in these white and negro crania.

The writer was particularly fortunate in being enabled to study the interorbital width in an interesting racial type like the Eskimo, which was represented by crania in the U. S. National Museum from the Greenland area. The male crania of this series were alone examined, and were found to present an average interorbital width as low as 21.7 mm., with a prob- able mean error of 20.2096. This measurement, as it hap- pened, was the lowest average for all the racial types repre- sentative of modern man that were available for this investi- gation. I t was certainly significant to have to record the fact that this average was as much as 5.45 mm. less than that for the Hamann Museum male negro crania. When one consid- ered the very large size of these Eskimo crania, with their average capacity of 1560 cc.(2), one became all the more impressed by the remarkable reduction of their interorbital widths.

The author’s next duty, if possible, was to investigate this dimension in another Mongolian type. Fo r this purpose he was enabled to study the male Mongol crania of the U. S. National Museum. The average interorbital width was much higher in these than in the Eskimo, the actual figure being 25.4 mm. Indeed, this measurement was nearly as great a s that for the Hamann Museum negro crania, and also definitely above the average for the white crania. It was thus evident that the contracted interorbital width of the Greenland Eskimo represented a definite degree of racial specialization, when compared with that for other Mongolian types, as

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shown, for example, by these crania from Mongolia. The author was greatly impressed by the marked reduction of the nasal width in the Eskimo crania of the Canadian Arctic Expedition, 1913-1918, for in his report(1) he stated that “its contracted nasal aperture, perhaps its most important specialisation, placed the Eskimo skull in a category by it- self.” The results of the present research tended to show that to this had to be added another marked example of a racial specialization in the Eskimo skull, namely, its con- tracted interorbital width.

The native Australian crania provided an average inter- orbital width of 23.8 mm. Only five crania were available to represent this racial group, and these were, moreover, under- sized specimens. There is thus a possibility that the racial average may be higher than this. An allied race, namely? the native Tasmanian, was represented by one skull in the Hamann Museum. It yielded an interorbital width of 24 mm. Another race with certain affinities with the above races, namely, the Melanesian, was represented by two crania in the author’s collection, each of which possessed an interorbital width of 26 mm. The dimensions furnished by these three racial types were, it may be noted, all below the average for the Hamann Museum male negroes. However, it is obvious that one can make no more than a preliminary statement regarding the average for this cranial dimension in the native Australian race.

TABLE 2

Among the racial types that were available, the average interorbital width was found to be greatest in the Humann Museum negro and least in the

Greenland Eskimo Ym.

Male negro (Hamann Museum), 27.15 f 0.2237 Male white (Hamann Museum), 24.6 2 0.2229 Male Eskimo (U. S. Natl. Museum), 21.7 2 0.2096

THE INTERORBITAL WIDTH I N FOSSIL MAN

As the original crania representative of fossil man, with the exception of the Gibraltar and Rhodesian skulls, were not

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accessible to the author, he had to be dependent upon excel- lent casts of these in the Hamann Museum. It was quite remarkable to note how readily the lachrymal point could be located in all the specimens that were available. For instance, in the Rhodesian skull the lachrymal crest was found to be indicated by quite a prominent ridge, the junction of which with the frontal bone could be easily detected. It may be added that Professor Wingate Todd concurred in the exact localization of the lachrymal point in these specimens. The La Chapelle skull was represented by both the Barlow and the Krantz casts, each of which recorded the same interorbital dimension, thus providing further justification for the study of these casts of the original crania.

The author decided to record the result for the Rhodesian skull first of all, for it was quite outstanding. This specimen yielded an interorbital width of 34.7 mm., which was, of course, to be regarded as excessive, and therefore noteworthy. It certainly gives a striking appearance to the published photographs of the facial aspect of this skull. An examina- tion of table 1 will show that this measurement was definitely above the maximum limit for this cranial dimension in all the crania that were available to represent modern man. Indeed, the only measurement that at all approached it was that yielded by one of the male negro crania, namely, 33.1 mm. Needless to say, it was f a r beyond the maximum limit for the European type of skull. The author is deeply indebted to Mr. W. P. Pycraft for the privilege of examining the Rhodesian skull.

The lachrymal point was not so well defined in the La Chapelle cast, so that the interorbital width of 29.5 mm. yielded by it will require to be accepted as merely approxi- mate. .In any case, it was f a r above the average yielded by the modern European type of skull. This cranial measure ment was capable of being estimated more readily in the Gibraltar skull, which furnished an interorbital width of 29 mm., which therefore accorded very closely with that shown by the La Chapelle specimen. It was thus rather inter-

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esting to note that these two crania representing Neanderthal man, that were discovered in Europe, displayed interorbital widths almost exactly similar, andwell above the average for the skull of the modern European. The author is deeply indebted to Prof. Sir Arthur Keith for the privilege of examining the Gibraltar skull.

The Galilee skull is, of course, very fragmentary, but the Hamann Museum contained an excellent cast. The left half of the interorbital width is wanting in this specimen. The writer was, however, able to measure its right half, and found it to be 13.5 mm. The total width would thus amount approxi- mately to 27 mm.

The Talgai skull from Queensland was also represented by a cast in the Hamann Museum. It was found that the inter- orbital width in this specimen could be measured with a fair degree of accuracy, and proved to be 29 mm.

The interesting point elicited from a study of these repre- sentative types of fossil man was as follows: Their inter- orbital widths tended to be higher than the averages for the white, the Mongolian, and the black races of modern man, that for the Rhodesian specimen being markedly so. The writer discussed these facts with Professor Wingate Todd, and as a result of our deliberations it was manifest that the La Chapelle, Gibraltar, and Galilee specimens, so f a r as their interorbital widths were concerned, could be grouped to- gether. That is to say, the interorbital width in the Galilee skull conformed to that found in the European type of Neanderthal man.

TABLE 8

The interorbital widths recorded by the crania of fossa m n . These measure- ments will require to be accepted as approximate, as three were made on

casts of the original crania Mm.

La Chapelle man, 29.5 Gibraltar man, 29 Galilee man, 27 Talgai man, 29

Rhodesian man, 34.7

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Much controversy has arisen regarding the inclusion of the Rhodesian skull as a representative of the Neanderthal type of fossil man. It is not the intention of the author to enter into any special discussion on this matter. However, he can- not resist a reference once more to the vast dimensions of the interorbital width in the Rhodesian skull, compared with those found in the La Chapelle, Gibraltar, and Galilee specimens, all of which were within the range of variation for the modern European skull. Indeed, he is surprised that no previous observer has directed particular attention to this remarkable feature of that skull, which distinguishes it so clearly from the so-called European type of Neanderthal skull. The pur- pose of the author in this paper is to record personal observa- tions and not conjecture. However, he is tempted to state that the extreme interorbital width of the Rhodesisn skull is as much a specific feature as some of the other specific fea- tures that have been mentioned in connection with this specimen.

The author was interested to note a very definite statement by HrdliGka(3) to the effect that “the skull itself is positively not the skull of any now known African type of man or their normal variants. Neither is it any known pathological mon- strosity, such as gigantism or leontiasis. It is a most remark- able specimen of which the age, provenience, history and nature are still anthropological puzzles. ” The present writer considers that a possible solution to this anthropological puzzle may be found on the shelves of the Hamann Museum. If those who are interested in this problem will visit this museum and inspect the vast series of negro crania displayed there in one continuous series, they cannot but be impressed by their remarkable interorbital widths. Is it not possible that the Rhodesian skull with its unusual interorbital width may represent an ancestral type for the African negro of to-day? At any rate, that appears to the writer a more feasible theory than that associating the Rhodesian man with the European type of Neanderthal man.

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COMPARATIVE ANATOMY OF THE INTERORBITAL WIDTH

The author made an investigation on this cranial dimen- sion in the three highest anthropoids, in which i t was found that it could be calculated very readily, as the lachrymal point was capable of being located with a fair degree of accu- racy. He was likewise intrigued by the remarkable reduction of the interorbital width in the skull of Tarsius.

This dimension was studied in the crania of five gorillas, in which it was found to vary from a maximum of 36 mm. to a minimum of 28.5 mm. The average dimension recorded by these crania was 32.9 mm. Four chimpanzee skulls were utilized for this investigation. These were, of course, much smaller than those of the gorilla series. The maximum width in these was 26.5 mm. and the minimum 23 mm., while the average proved to be 24.4 mm. As is well known, the reduc- tion of the interorbital width is quite a marked feature of the orang skull. This genus was represented by three crania, the maximum dimension for which was 17 mm. and the minimum 14.3 mm., while the average was found to be 15.5 171111.

The study of the interorbital width in two skulls of Tarsius seemed worthy of being recorded. One of the great features of this genus is, of course, its relatively enormous orbital apertures, which encroach to a marked degree upon both the cranial and facial portions of the skull. For instance, the writer noted that the orbital margins were prolonged back- ward on the lateral aspects of these skulls so much that they merged with the postorbital constrictions. The result was that the latter, which are, of course, a marked feature of the crania of lower mammals, were very slightly shown. As ft

consequence, the transverse dimensions of these crania, measured a t the site of their postorbital constrictions, were almost exactly the same as their maximum parietal breadths, the respective figures being 22.3 mm. and 23 mm. Both these measurements were exactly the same for each skull. The encroachment of the orbital margins on the facial portions of these tiny skulls was jus t as pronounced. The result was that the interorbital width in both cases was reduced to the

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small measurement of 2 mm. The appearance presented by the facial aspects of these two crania was certainly very quaint and, indeed, bizarre.

CONCLUSIONS

1. The interorbital width is a new cranial dimension. It is described for the first. time in this paper.

2. It is the distance between the right and left lachrymal points, the latter being defined as the points of junction of the upper ends of the lachrymal crests with the frontal bone.

3. It was studied in the Hamann Museum white and negro crania, and also in Eskimo, Mongolian, native Australian, native Tasmanian, and Melanesian crania.

4. The greatest average interorbital width was found in the Hamann Museum negro crania and the lowest in the Greenland Eskimo (U. S. National Museum). The average dimension for the Hamann Museum white crania occupied a position intermediate between these extremes.

5. The interorbital width of the Greenland Eskimo repre- sents a definite degree of racial specialization, when compared with that for other Mongolian types.

6. The interorbital width in the Galilee skull conformed to that found in the European type of Neanderthal man. On the other hand, the interorbital width in the Rhodesian skull was very great in comparison with those found in the La Chapelle, Gibraltar, and Galilee specimens, all of which were within the range of variation for the modern European skull. The measurements for the fossil crania will require to be taken as approximate, as they were made on casts. The Rhodesian and Gibraltar crania were, however, accessible to the author.

7. The author is inclined to regard the vast interorbital width of the Rhodesian slrull as a specific feature, which pre- cludes any association of it with the European type of Nean- derthal man.

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LITERATURE CITED

1 CAMERON, JOHN 1993 Report of the Canadian Arctic Expedition, 1913-1918,

2 HRDLIJCKA, ALES 1924 Catalogue no. 2480, United States National Museum,

3 1926 The Rhodesian man. Am. J. Phya. Anthrop., IX. 4 MARTIN, RUDOLF 1928 Lehrbuch der Anthropologie, Bd. 11. Jena.

XII, pt. c .

Washington.