DIFFERENCES I N T H E PATTERN OF THE SECOND LOWER MOLAR TOOTH LOUIS R. SULLIVAN American Museum of Natural History, New York City It is well known that the third upper molar and the second lower molar teeth are unstable in form, the former tending to become secondarily tritubercular and the latter secondarily quadritubercular. Accurate statistical data on the frequency of these transitions in the various types of mankind are not, with a few exceptions, easily accessible. For the most part such data lie buried in the body of larger craniometrical treatises and even here we find only occasionally accurate percentages based on a sufficiently large number of cases t o warrant their being accepted as an indication of the true state of affairs. This is by no means the fault of the various observers but may be attributed in the most part to the condition of the skeletal material. In all collections of crania, mandibula are present in only a small percentage of cases. Of this number a large proportion has lost the teeth in life or after death, some even in the process of collecting and storing. I n still another large percentage the teeth are worn t o such a degree that relatively few remain suitable for the study of cusps and tooth patterns. We have it on the authority of dentists that modern European man shows in a large majority of cases the secondary quadritubercular pattern in the second lower molar teeth. This observation is borne out by statistical studies in several collections of European crania. The hypoconulid disappears, leaving only the four cusps protoconid, metaconid, hypoconid, and entoconid. This is apparently a late development since the Mauer mandibula shows the primitive five cusps in the second lower molars as do also certain Neanderthaloid mandibula. Cunningham says the second lower molar has four cusps as a rule, five in only 24 per cent of all skulls examined. Martin gives the occurrence of 5 cusps in 6 per cent of Europeans and 15 per cent of the Lapplanders. Schwerz gives the following data: five cusps in 73 per cent of the Australians, 34 255 AMER.JOUR.Pays. ANTHROP.,VOL. III., No. 2 256 LOUIS R. SULLIVAN per cent of Negroes, 3 per cent of Alamans and 2 per cent of Hungarians. The number of cases upon which these percentages are based is not stated. HrdliEka52on the basis of teeth of the Munsey, Arkansas, Louisiana, Zuni and some Mexican Indians, gives the frequency of five cusps as 21 per cent; of 4% cusps as 25 per cent; and of 4 cusps as 54 per cent, But in 67 second lower molars of the Sioux he observed five cusps in 68 per cent, 4% cusps in 6 per cent, and 4 cusps in 36 per cent of the cases. In the male Sioux the proportion of the teeth with 5 cusps reached in fact as high as 77 per cent, that of 4 cusps being reduced to 20 per cent. There are in the American Museum of Natural History two collections of mandibula3 especially favorable for the study of tooth patters. The first is a group of 43 Tarascan Indians from Mexico and the second a group of 30 crania from southern India. The latter collection consists largely of crania of the modified Mediterranean type similar t o the Singhalese described by the Sarasin brothers. A few approach the Veddah type. Both of these series are made up almost wholly of young adults with complete dentition and show little or no wear. The condition in the two groups are quite different. In the collection of Tarascan Indians from Mexico the second lower molar has 5 cusps in 76.8 per cent of the cases and 4 cusps in only 23.2 per cent. The mandibulse from southern India on the other hand show five cusps in only 16.6 per cent of the cases and four cusps in 83.4 per cent. These results as well as those mentioned above may be summarized as follows. NUMBER OF CUSPS ON THE SECOND LOWER MOLAR TEETH Percentage Group Negro .......................... Southern India. . . . . . . . . . . . . . . . . . Lapplander ....................... European. ...................... Alaman ......................... Hungarian ...................... Author ? 30 ? ? ? ? 5 CUD8 4 CUSW 76.8 73.0 34.0 16.6 15.0 6.0 3.0 2 .o 23.2 27.0 66.0 83.4 85.0 94.0 97.0 98.0 Sullivan Schwerz Schwerz Sullivan Martin Martin Schwerz Schwerz That the condition found in the Tarascan Indians may be taken as representative of the condition in a t least some American Indians I feel fairly certain. It has been my experience that a second lower molar tooth with only four cusps is relatively rare in American Indians. MOLAR TOOTH 257 I n the case of the Tarascan Indians the fifth cusp (hypoconulid) in question is in a majority of cases as large and well formed as is the corresponding cusp in the Mauer jaw and the tooth correspondingly large. Whether the differences revealed in the above table are indicative of racial or functional differences is not quite clear. The Australians and the American Indians stand close together in this particular characteristic yet they are undoubtedly quite distinct racially. The Negro, famed for his supposedly perfect and primitive dentition, is apparently quite modern and specialized in this particular respect. The Europeans are uniform in showing a high percentage of cusp reduction. It is obvious that more detailed data are needed before generalizing on the cause of this reduction. From the above it is not altogether clear how closely this reduction is correlated with the diminution of function. While the skulls from southern India show a high percentage of cusp reduction their dentition can in no sense be considered degenerative. They show a very high percentage of normal occlusion and the teeth are in most cases well formed and free from caries. The reduction in question is important from an evolutionary standpoint and worthy of separate study. It is for this reason that the above observations are placed on record. It is to be hoped that more data will be forthcoming on the Negroid and Mongoloid types. BIBLIOGRAPHY Cunningham, D. J.-Textbook of Anatomy. Edited by Arthur Robinson, New York, 1917. HrdliEka, Ales-Physical Anthropology of the Lenape or DeIewares, and of the Eastern Indians in General. Bureau of American Ethnology, Bulletin 62, 1916; Skeletal Remains from Arkansas and Louisiana, J. Ac. Nat. SC. Phila., 1909, XIV, 209 and personal information. Martin, Rudolph-Lehrbuch der Anthropologie, Jena, 1914. Schwerz, Franz-Die Volkerschaften der Schweiz von der Urzeit bis zu Gegenwart, Buschan, Studien und Forschungen zur Menschen-und Volkerkunde, Vol. XIII, Stuttgart, 1915.