PROPORTION B E T W E E N INTERORBITAL WIDTH

ITS SIGNIFICANCE I N MODERN AND FOSSIL MAN

AND FACIAL HEIGHT. A N E W CRANIAL INDEX;

JOHN CAMERON

CRANIOMETRIC STUDIES, No. 30

This paper is a direct sequel to Craniometric Study no. 28, in which a new cranial dimension, termed the interorbital width, was described by the author. I n the present paper a re chronicled the results of a study of the proportion which this new cranial dimension bears to the facial height. It is essential to state at this stage that the term ‘facial height,’ which will be referred to throughout this paper, will refer in every instance to the maxillary facial height, as measured from the nasion to the alveolar point. The cranial material from the Hamann Museum that was utilized in this research consisted of sixty male white, sixty female white, sixty male negro, and sixty female negro crania. The writer wishes to express his best thanks to Prof. Wingate Todd for all the valuable facilities accorded to him during this research. The author was also enabled to calculate this new index in thirty male Greenland Eskimo, fifteen male Mongol, and five native Australian (unsexed) crania in the United States National Museum, thanks to the kindness of Dr. Ale; HrdliEka.

I n calculating this new index the facial height was taken as representing 100. The index was therefore obtained from the following formula:

Iuterorbital width X 100 Facial height

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237 AMERICAN JOURNAL O F P H Y S I C A L ANTHROPOLOGY, VOL. XVI, NO. 2

OCTOBER-DECEMBER. 193 1

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The figure yielded by this formula represented the percent- age relationship which the interorbital width bore to the facial height in any given skull.

This new index was found to display the usual wide ranges of variation in the various racial types that were available. The range shown by the male white crania was, however, quite excessive, namely, 22.9. As the average interorbital width/ facial height index was found to be highest in the representa- tives of the black races, one would have expected them to dis- play also the highest maxima. Thus it will be noted in table 1 that very high maxima were exhibited by the negro and native Australian crania. These mere overtopped, however, by one male white skull (no. 934 in the Hamann hluseum), which presented the very high index of 50.1. This abnormal result was explained by the relatively great interorbital width and the unusually low facial height possessed by this skull. All the other white crania, it may be observed, showed indices lower than the maxima for the negro and native Australian crania. The Eskimo crania presented a relatively small range of variation, which one would be led to expect in a com- paratively homogeneous race. The small range shown by the native Australia11 crania was explained by the relatively small numbers available for examination.

TABLE 1

The ranges of variation of the interorbital width/facial height indez Maximum Minimum Range

Hamanii Museum male white, 50.1 27.2 22.9 ITamann Museum male negro, 45.2 28.3 16.9 Male Eskimo (U. S. A'ational Museum), 35.2 25.1 10.1 Male Mongol (U. S. National Museum), 43.5 24.4 19.1 Australian native (U. S. National Nuseum), 44.6 36.5 8.1

The standard deviations and coefficients of variability of the interorbital width/facial height index were calculated in the cases of the white, negro, and Eskimo crania. The crania representing the other racial types were obviously too small in number for the carrying out of these calculations. It was rather interesting to record the fact that the male white and

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male negro crania yielded exactly the same standard devia- tion. The standard deviation was significantly low in the male Eskimo crania, in contrast to the higher deviations dis- played by the more heterogeneous white and negro racial groups. The coefficients of variability followed the standard deviations consis ten tly.

TABLE 2

The siandard deviations and coefficients of variability of the interorbital width/ facial height index

Hainaun Museum male white, 3.901 C 0.2401 10.98 C 0.67603 IIalnaiiii Museum male negro, 3.901 C 0.2401 10.45 C 0.6434 Male Eskimo (U. S. Natioual Museum), 9.72 ? 0.8466

S.D. a. of v.

2.85 C 0.2482

T H E AVERAGE INTERORBITAL WIDTH/FACIAL HEIGHT I N D E X IN MODERN M A N

The average index for the male white crania was found to be 36.01 (2 0.3396). This result, when interpreted, meant of course that the interorbital width was, on the average, 36.01 per cent of the facial height in this racial group. On the other hand, the average index f o r the male negro crania was ascertained to be slightly higher, namely, 38.2 (A 0.3396). This result indicated that the interorbital dimension was rela- tively wider in proportion to the facial height in this racial group, when contrasted with the white crania.

This racial difference was exhibited also by the Hamann Museum female crania. Thus the average interorbital widt,h/ facial height index for the female white crania proved to be 35.5, while in the female negro crania it was again higher, namely, 38.6.

The lowest average for this index in the racial types that were available for study was found to be that yielded by the Greenland Eskimo male crania of the U. S. National Museum. This cranial group furnished a n index of only 29.3 ( 0.3514), which was to be accounted for by two factors. The first of these was a remarkable reduction of the interorbital width in these Eskimo crania, as described in Craniometric Study no. 28, while the second factor was an increase in the facial

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height, when compared, for example, with the average facial height of the European type of skull(1).

The author’s next duty was to study the interorbital width/ facial height index in another Mongolian racial type, as repre- sented by the male Mongol crania of the U. S. National Museum. These yielded a n average index of only 32.7, which, like that for the Eskimo, was definitely lower than the aver- age for the Hamann Museum white crania. This reduction in the index was not due to a diminution in the interorbital dimension, which, as shown in Craniometric Study no. 28, was actually greater than the average for the white crania. I t was therefore due to a remarkable increase in the facial height of these Mongol crania, which, as the author has recently shown( 1)’ was definitely greater than the average facial height as found in the European type of skull. This marked increase in the facial height would, of course, have the effect of lowering the interorbital width/facial height index.

The average interorbital width/facial height index for the native Australian crania of the U. S. National Museum proved t o be 38.8, that is to say, almost exactly the same as the average for the Hamann Museum negro crania. This result was due not so much to an increased interorbital dimension, but to a marked reduction in the facial height in this racial group. This figure will have to be accepted as purely tenta- tive, as it probably does not represent the true average, see- ing that only five native Australian crania were available. Nevertheless, from the data that have been collected so far, one is enabled to affirm that this new cranial index was found to be highest on the average in the black races and lowest in the Mongolian types, with the white races occupying a more or less intermediate position between these, as shown in table 3. I t was thus evident that the index displayed a fair degree of racial consistency.

The aboriginal Tasmanian was represented in the Hamann Museum by a single skull. The writer therefore decided to investigate its interorbital width/facial height index as an appropriate sequel to the study of the native Australian

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group. The index for this skull was very high, namely, 43.2. This extreme figure was due, as in the Australian crania, not so much to an increased interorbital dimension, but to a marked reduction in the facial height. The latter dimension registered only 55.5 mm. in this skull, which, of course, would have a marked effect in raising the index.

TABLE 3

W i t h the raoial types so fa r at the autlwr’s disposal, it was ascertained tluzt the average interorbital width/facial height indez was highest in the black races and lowest in the Nongolian racial types, with the white races occupying a more or less intermediate position between these.

Black races Native Australian (U. S. Natioiial Museum), 38.8 Male negro (Hamaiiii Museum), 38.2 Female negro (Hamanu Museum), 38.6

White race# Male white (Hamaiin Museum), Female white (Hamanu Museum),

36.01 35.5

Mongolian races Male Mongol (U. S. National Museum), 32.7 Male Eskimo (U. S. National Museum), 29.3

THE INTERORBITAL WIDTH/FACLAL HEIGHT I N D E X IN FOSSIL MAN

The casts of four crania of fossil man were available in the Hamann Museum for this portion of the investigation, namely, those of the Rhodesian, La Chapelle, Gibraltar, and Talgai skulls. The writer was fortunately enabled to make the necessary measurements on the original skulls in the cases of the Gibraltar and Rhodesian specimens, thanks to the kind- ness of Sir Arthur Keith and Mr. W. P. Pycraft. It may be added that these calculations agreed with those made on the casts of these two crania, which was a tribute to the accuracy and care exercised in the preparation of these casts. The indices for the La Chapelle and Talgai crania will, however, require to be taken as approximate, owing to the fact that the requisite measurements had perforce to be made on casts.

The La Chapelle specimen presented an index of 36.8, which was comparable to the average for the modern Euro- pean type of skull, as given in table 2. The Gibraltar skull gave an index definitely higher, namely, 40.2, even though

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its interorbital width was fractionally less than that of the La Chapelle cast. The difference was, of course, explained by the greater facial height of the l a t t e r 4 0 mm., as against 72 mm. for the Gibraltar skull.

The Talgai cast provided an index as high as 43.9. It was of interest to record the fact that this was due to the same cause which gave the high index for the Australian native crania, namely, a marked reduction in the facial height. The latter measured only 66 mm. (approximately) in the Talgai cast.

The Rhodesian skull yielded an index of only 37.9, even though its interorbital width was easily the greatest for all the crania, both modern and fossil, that were examined. This extreme dimension was partially neutralized by the facial height of this specimen, which registered the remarkable measurement of 91.5 mm.

CO~CLUSIONS

1. The interorbital width/facial height index is a new cranial index which has been devised by the author. It is described for the first time in this paper, which is a prelimi- nary communication. It is suggested as a possible line of research for other investigators who have access to large collections of crania representative of racial types that were not available to the writer.

2. From the racial material so f a r at his disposal, the author ascertained that the average interorbital width/facial height index was highest in the black races and lowest in the Mongolian races, with the white races occupying a more or less intermediate position between these.

3. The Gibraltar and Rhodesian crania and casts of the La Chapelle and Talgai skulls were available to the author as representative of fossil man. The indices of these proved of great interest, but of course those relating to the latter two would require to be taken as merely approximate.

LITERATURE CITED 1 CAMERON, JOHN 1929 The facial height as a criterion of race. Amer. J.

Phys. Anthrop., XIII .