CUSP DEVELOPMENT ON THE SECOND LOWER MOLARS I N THE BANTU AND BUSHMEN

J. C. MIDDLETON SHAW University of the Witwatersrand, Johannesburg

It is well known that the second lower molar tooth in modern European man is, in the majority of cases, of the quadricuspid type. The hypoconulid, or fifth cusp, has disappeared, “nearly all traces of the Dryopithecus pattern are lost,” and, instead, we have a four-cusped type of tooth with an +- shaped occlusal surface. In 1920, Mr. Louis R. Sullivan, of the American Museum of Natural History, pointed out that accurate statistical data concerning the pattern of the second lower molar in many of the various types of mankind are either inaccessible or non-existent.

It has been my fortune during the past two years to have had the opportunity of examining the dentitions in a large number of South African Bantu and Bush races and of ob- taining accurate data concerning the cusp formula of the second lower molar in the dentitions examined.

Numerous reports on the pattern of this tooth in Bantu races have been published formerly, but in many cases the percentages have been based on an insufficient number of specimens to warrant their being accepted as representing the true state of affairs in these races. In Bush races, on the other hand, so fa r as 1 am aware, records of the pattern of the second lower molar are extremely rare, if not entirely lacking.

During this investigation there were examined the teeth in part of the large collection of skulls from the anatomy museum of this university. This collection of skulls has been classified as foIlows :

97 AMRRIC4N JOTRNAL O F PHYSICAL ANTIIROI’OLOGY, \ O L . XI, N O . 1

OCTOBER-DECEMBER, 1927

98 J. C. MIDDLETON SHAW

Bantu Bush Bush-Australoid

hybrid

1. Bantu skulls, 78 specimens. 2. Bush skulls, 32 specimens. 3. Skulls of Bush-Australoid (Broom, '25) hybrids, 1 0 specimens. Total number of skulls in this collection, 120.

In the second place, there were examined the second lower molar teeth in 118 South African Bantus attending at the Witwatersrand University Dental Clinic. I n all, theref ore, there mere examined the second lower molars in 196 Bantu people, in 32 Bush people, and in 10 Bush-Australoid hybrids.

It is considered that a sufficient nrimber of Bantu teeth have been examined to warrant the conclusion that the data ob- tained do represent the true state of affairs in Bantu races.

TABLE 1

Nwmber o f cusps on the second lower molar teeth

196 10s 88 55.1 44.9 32 S 24 (25) (75) 10 8 2 (80) (20)

PERCENTAQE 5 CUSPS. 4 cusps.

GROUP ~ X?GiiR ~ NUMBER ~ NUMBEB ~

OBSERVED OBSERVED OBSERVED cusps I 4 cusps

The number of Bush and Bush-Australoid teeth examined, although perhaps not numerous enough to warrant a similar conclusion, provides reliable evidence concerning the pattern of the second lower molar in the majority of these peoples. Fo r these reasons, a report on the data obtained appears to be justified.

The number of cusps on the second lower molar in the dentitions examined is shown statistically in table 1. It will be seen from that table that slightly over 50 per cent of Bantu people possess lower second molars with five cusps and that only eight of the thirty-two Bush dentitions examined exhibit a similar number of cusps on that tooth. On the other hand, the second lower molars in eight of the ten Bush-Australoid dentitions examined arc of the quinquecuspid type.

CUSP DEVELOPMENT ON SECOND LOWER MOLARS 99

It has frequently been stated that negroid races show a high percentage of cusp reduction and are, in this respect, modern and specialized. The South African Bantu material available for study here does not confirm this opinion. The hypo- conulid is present on the majority of the second lower molar teeth of Bantu races examined by me, and only in 45 per cent of cases was the hypoconulid absent and the occlusal surfaces of the crowns of the +-shaped form,

The high proportion of cusp reduction in the Bush denti- tions examined was not unexpected, for it has been my ex- perience to find that degenerative changes are constantly ob- servable in many of the teeth of Bush races. Thus, the third molar teeth are frequently reduced in size and unstable in form; the second maxillary incisors are often dwarfted teeth and are sometimes entirely absent.

The presence of the primitive five cusps on the lower second molars in eight of the ten Bush-Australoid dentitions available for investigation is of special interest.

It has been stated that “there is evidence of the intrusion of an Australoid strain into many of the Bush races” and that “there is a possibility that an Australoid strain may be found mixed with all the different yellow-skinned races of Southern Africa. ” Doctor Broom ( ’25), after pointing out that it is possible that an Australoid race once inhabited southern Africa, states that in some South-African peoples supra-orbital ridges are developed “as in the average male Australian,” and that this character “has possibly been de- rived from the race represented by the Broken Hill skull’’ (i.e., Homo rhodesiensis).

The skulls of the Bush-Australoid hybrids examined during this investigation are remarkable not only because they ex- hibit well-developed supra-orbital ridges, but also because the teeth in these skulls are exceedingly well-formed and regu- larly placed and the dental arches unusually well-developed.

As has been shown above, well-f orrned and regularly placed teeth are not characteristic of pure Bixsh races. It therefore seems possible that these dental characters in the Bush-

100 J. C. MIDDLETON SHAW

Australoid hybrids are characters acquired as the result of the Australoid intrusion.

If quinquecuspid, well-formed, regularly placed teeth in Bush-Australoid hybrids are the result of the Australoid in- trusion, we are justified in assuming that the teeth of the South-African Australoid race were of a more primitive type than the teeth of any known living South-African race.

Whether the dental characters observed in these hybrids are the result of the Australoid intrusion or not, we must believe that some very primitive strain is present in the Bush- Australoids and is responsible for the conditions recorded here.

It may be pointed out that, so far as cusp reduction is con- cerned, the Australian aboriginal, famed for his supposedly primitive type of dentition, is more modern and specialized in this particular respect than these Bush-Australoid hybrids. Schwers (quoted by Sullivan, '20) states that 73 per cent of the Australian aboriginals exhibit five cusps on the lower second molar. Campbell ('as), however, after an examina- tion of 125 specimens, informs us that only 32 per cent of the aboriginals possess lower second molars of the quinquecuspid type.

These observations show that study of the teeth in South- African races has not attained the position of importance that it should and, no doubt, will attain. It seems possible that, if the subject could be studied statistically, the pattern of the molar teeth in primitive African races would afford valuable evidence of the evolutionary stages by which the modern pat- terns of molar teeth have been reached.

BIBLIOGRAPHY

ALLEN, A. L. 1926 A report on the Australoid calvaria found a t Mistkrall. S. Afr. J. Sc., XXIII , 943-950.

BROOM, R. A contribution to the craniology of the yellow-skinned races of 9. Africa. J. R. Anthrop. Inst., LIII, 132-149.

CAMPBELL, T. D. 1925 The dentition and palate of the Australian aboriginal. Publ. under the Keith Sheridsn Foundation, no. 1. Adelaide, 14, 15.

SULLIVAN, L. R. 1920 Differences in the pattern of the second lower molar tooth.

1925

Amer. J. Phys. Anthrop., 111, 255-257.