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Discreta of the human skeleton: a critical review
F. W. R6sing
Discreta of the Human Skeleton: a Critical Review
Abteilung Anthropologie und Wissenschaftsforsehung, Universitlit Ulm, Ulm, West Germany
Published results concerning, and unpublished experiments with discreta (discrete or quasi-continuous traits) suggest that analysis of such traits is plagued with serious difficulties, particularly a virtually unknown genetic background and the lack of a standard for their definition and determination. Thus, this trait complexappears to be unsuited for most populational investigations.
1. I n t r o d u c t i o n
The purposes of this paper are: (1) to give a general review of present knowledge regarding quasi-continuously variable traits (discreta/"epigenetic" traits/anatomical variants), and (2) to substantiate the wide spread doubts about the theoretical foundation of these traits, which are seldom formulated in papers but are practically always part of oral treatment of the topic. A review of this topic is appropriate at the present time, because a shift in orientation is evident in papers dealing with this theme. The period of large initial considerations has passed. The traits examined consist of: (1) variants of bone numbers and suture configurations, (2) numerical and shape variants of foramina, (3) hyperostotic (and hypoostotic) variants, (4) numerical and shape variants of teeth. This classification shows that discreta are heterogeneous. Their only common characteristic is their small size. For designation of this trait complex "quasi-continuous traits" is recommended, or as a short, and less precise, term "discreta". "Epigenetic traits" and "non-metric traits", however are inappropriate for several reasons. For example, the term "genetic" is often understood to be a characterizastion of these traits, but their genetic determination is largely unknown. Furthermore, if we trace back "epigenetic" to the epigenesis theory of Wolff (1759), then every trait complex which is generally measured or observed should be included. The trait names in this paper are in latin, following the latest proposal by I~lesnys & Pavilonis (1982). The present wide-spread interest in discreta stems mainly from a paper by Berry & Berry (1967). It must be stressed that this work is defective in most of the critieria of scientific quality which can be formulated (dogmatic genetical statements without material basis, lack of differentiation between traits and between animal species, criticism of other trait complexes without adequate knowledge of them, different or contradictory interpretation of the same results). Its value rests upon its stimulation of further research. 2. G e n e t i c s
The most important basic property of any trait in physical anthropology is its genetic determination. There are m a n y older papers which contain conclusions like: "determined by three loci", "one dominant autosomal gene", "high penetrance and expressivity" etc. These statements should be regarded as history, typical examples of a period in science in which genetics was totally restricted to simple categories. Journal of Human Evolution (1984) 13, 319-323
0047-2484/84/040319 + 05 $03.00/0
9 Academic Press Inc. (London) Limited
320
F.w. R6sINe
Today we may presume that discreta are determined by a large amount of hierarchically organized genetic information, just as in the case of measurements or traits reflecting shape. Thus, as in the case of these latter trait complexes, genetic determination may best be described by heritability measures. If we check the literature for precise heritability information on quasi-continuous traits, we find first that there is not even one publication on the whole trait system in humans. We find only information on single traits (e.g. Garn, 1966; Saunders & Popovich, 1978) and information on mice (Self& Leamy, 1978) and macaques (Cheverud & Buikstra, 1981). As a general conclusion, it must be stated that only a small minority of discreta is known genetically. More specifically: six to eight traits can be regarded as predominantly determined genetically, and two frequently used traits are predominantly non-genetic (foramen infraorbitale accessorium and foramen zygomaticofaciale accessorium). This is a very meagre level of knowledge in the face of the fact that the average number of traits employed in recent papers is 28 and that the number of traits determined in at least one single population in the last decade surpasses 120.
3. Correlations and Variability A thorough examination of the literature reveals only a few significant inter-trait correlations, but here again information is sparse and partly contradictory. Several studies conclude that there are few traits which exhibit significant sex differences and none which exhibits significant sex differences across several populations. Age variability is sufficiently known. For hyperostotic variants, age dependence is known to be high, or may be presumed to be high (e.g. Buikstra, 1972). All other traits are age-independent (e.g. Perizonius, 1979a). Asymmetry of bilateral traits is negligible, even if we take into account that different questions may be being asked (for side preference or for symmetry preference). Only one paper (Kellock & Parsons, 1970a) contains information on trait-specific variability between populations. In this study ten traits already account for 90% of the total variability among australoids. This topic should certainly be investigated further, as it at least gives an objective criterion for the selection of specific traits to be included in population analyses.
4. Methods According to the experience of the author of this paper, at least half of the 40 traits most commonly used are ill-defined in the literature. Particularly the description "extra-sutural" is far from being unequivocal, and it might even be suspected that it is basically impossible to define discontinuous manifestations of this characteristic. This means that frequencies by different workers are not comparable (see also Molto, 1979; Thoma, 1981). A direct check of the inter-observer error (Finnegan & Rubison, 1980) revealed devastatingly high deviations for several traits. This restricts the applicability of discreta to analyses of data by only one individual investigator. Thus, at the present time the methodology of quasi-continuous traits is in a developmental stage comparable to that of metric traits before the Frankfurt Verst~ndigung of the last century.
321
DISCRETA OF THE HUMAN SKELETON
5. Applications The majority of population comparisons published so far seems to yield meaningful results which are comparable to or supplement other knowledge about human populations. Yet one of the best papers in the field (Thoma, 1981) concludes that there is "nonsense variation" between races. In general, there is a tendency to find more meaningful results if the populations are more closely related to each other. This suggests that discreta might be better applicable to small-scale analyses (see also Brothwell, 1959, p. 93). Some population biological processes have ben analysed by means of discreta (e.g. Table 1
Familial differentiation of discreta in the Aswan necropoles Qubbet el Hawa and Elephantine. n-no. of variants, N-no. of individuals, %--relative frequency of variants, P . x 2 significance in % in comparison with total I, total I - o b s e r v a t i o n s on socially determinable and clearly dated individuals, total II--all observations. Both sexes and all ages pooled Total I n/N %
Total II n/N %
1 Sutura metopica 18/447 4'0 29/675 4"3 2 Foramen supraorbitale 77.5/441 17'6 115'5/667 17"3 3 Sulcus frontalis 96'5/441 11"9 133/664 20"0 4 0 s s a suturae coronalis 27 5/401 6"9 35/603 5'8 5 0 s bregmae 2/395 0-5 2/592 0-3 6 0 s s a suturae sagittalis 11/377 2"9 16/556 2'9 7 Foramen partietale absens 145/432 33"6 214/649 33"0 8 0 s lambdae 42/399 10'5 59/601 9'8 9 0 s incae 11/420 2"6 17/629 2-7 10 Ossa suturae lambdoideae 135/407 33'2 211'5/610 34"7 11 Os asterii 32/408 7-8 48/625 7-7 12 Os incisurae parietalis 39/406 9'6 58'5/623 9"4 13 Canalis condylaris abs. 99/389 25"4 146/589 24"8 14 Canalis hypoglossi acc. 70/398 17'6 107/605 17"8 15 Facies cond. bipartitus 0-5/394 0"1 0'5/601 0"1 16 Tuberculumpraecondylare 50'5/394 12'8 71"5/600 11"9 17 Foramen ovale incompl. 5.5/397 1"4 8"5/606 1-4 18 For.spinosum incompl. 58'5/393 14'9 84/598 14"0 19 Foramen Huschkei 37.5/415 9"0 53-5/628 8"5 20 For, mast, extrasuturae 139"5/398 35"1 219/608 3 6 - 0 21 Foramen mastoideum abs. 57.5/398 14"4 83-5/609 1 3 " 7 22 Torus acusticus 4/421 1'0 4/643 0"6 23 Os pterii 50/362 13"8 70"5/573 12"3 24 Sutura frontotemporalis 9/372 2"4 12/584 2"1 25 For. ethm. ant. extras. 52-5/245 21"4 82-5/381 21"7 26 For. ethm. post. absens 34'5/277 12'5 40/453 8"8 27 For. infraorbitale acc. 11.5/334 3"4 21"5/509 4"2 28 Torus palatinus 0/354 0'0 0/537 0'0 29 Toruis maxillaris 7.5/359 2"1 9/540 1"7 30 For. palatinum majus abs. 9/336 2'7 21'5/512 4"2 31 For. palat, minus absens 9/325 2"8 13"5/499 2"7 32 For. palat, minus acc, 181'5/322 56'4 25'7/496 51"8 33 For. zygom'faciale abs. 34.5/365 9"5 45"5/552 8"2 34 For. zygom'faciale acc. 194/366 53'0 304/552 55'1 35 M3 maxillae absens. 42/339 12-4 39-5/485 8-1 36 M3 mandibula abs. 23"5/260 9'0 39/370 10-5 37 Torus mandibularis 6.5/279 2"3 7"5/413 1"8 38 For. mentale accessorius 12/280 4'3 16'5/413 4'0
Grave 88 n/N %
P
1/62 1"6 13/62 21'0 9"5/62 13"7 1"5/56 2"7 t/54 1-9 1/54 1"9 15/59 25"4 6/56 10"7 1/59 1'7 205/58 35"3 2"5/59 4"2 3"5/60 5'8 10"5/51 20"6 8/54 14"8 0/54 0"0 6/55 10"9 0"5/54 0'9 7"5/53 14"2 11/59 18'6 2'27 t7"5/56 31-3 6"5/56 11'6 0/60 0'0 3"5/49 7"1 1/53 1"9 4/27 14'8 2/34 5'9 1/45 2"2 0/49 0"0 0/49 0"0 2"5/45 5'6 0-5/44 1"1 24/43 55"8 2"5/52 4"8 31/53 58"5 3-5/44 8-0 0"5/51 0"9 4"89 0/54 0"0 4/54 7"4
Grave 89 n/N % 2/35 3/33 12'5/33 4/32 0/32 0/36 17/35 2/34 1/33 13"5/36 6/35 7"5/34 10/32 9/32 0/33 15-5/33 1/33 8/33 3/34 14-5/32 4"5/32 2/34 2"5/29 1"5/30 5/22 9/24 0'5/26 0/30 0/31 0/30 3"5/29 13/28 3'5/30 17/30 2/31 3/17 1/18 1/18
5'7 9-1 37"9 12"5 0-0 0"0 48"6 5"9 3"0 37"5 17"1 22-1 31"3 28-1 0"0 47-0 3"0 24-2 8"8 45-3 14"1 5"9 8"6 5-0 22"7 37-5 1"9 0"0 0"0 0"0 12"1 46-4 11"7 56-7 6-4 17-6 5'6 5"6
P
3"53
2-32
0'00
1-98
0"08
0"93
322
v . w . R6SINO
migration/gene flow, isolation/fbunder effects and selection). A first example for the use of discreta to investigate social assortment or isolation is given in the original paper (R/Ssing,
1982). Under favorable conditions, individual relationships might be analysed by means of discreta. An example of markedly different familial occurrence of several traits is given in Table 1. Both Aswan necropoles belonged to the same settlement, but differ in the social status of the grave owners. Both are dated from the end of the 5th dynasty to the 12th dynasty ("total I" of Table 1) or the 26th dynasty ("total I I " ) . The table gives observations from two graves which are neighbors and closely related in size and quality. Family grave 88 has rather "normal" frequencies, whereas 89, despite the smaller group size, is untypical of this population. A further analysis might reveal such things as which individuals married into the family 89.
6. Conclusion I f we compare the properties of discreta to those of other skeletal traits we arrive at the following synopsis:
Information level Genetics, known simple determination genomerepresentation Trait intereorrelation Sex variation Age variation Comparable to living to other groups Method standardization determination problems Individual representation Determination time General esteem
Discreta
Measurements Shapetraits
Si:rology
Low Poorly Yes? High? Moderate? Low? Rare Low No Poorly No Yes High (Low) (High)
High Well No Moderate High High Yes Yes Yes Well Yes No Low Moderate High
Low Very well Yes Very high Low Very low No No Yes Poorly Yes No (Total) High Moderate
High Moderately No Moderate? High Moderate Yes Yes Yes Poorly No Yes High Higher Low
The majority of the statements in this table may be substantiated by theoretical arguments or literature; moreover, they are based on numerous personal communications from experts in this field. Several entries in this table demand further explanation. In the case of shape traits and serology, the degree of knowledge about the genetics is, of course, based only on studies of living groups. "Determination" means the relative part of trait variances determined by genetic information as oppposed to environmental influences. The line "comparable to other groups" condenses the number of groups already studied and published, which may be used for comparisons. "Individual representation" means, for example, that in the frequently occurring case of incomplete or fragmentary skeletons, measurements may not be taken but a greater number ofdiscreta and theoretically the ABO blood groups of every individual may be determined. The statement on "determination time" in the case of discreta had to be placed in brackets because the lack of standardization frequently creates time-consuming problems. General esteem for discreta seems very high only if we count
DISCRETA OF THE HUMAN SKELETON
323
published statements. Oral statements, however, are almost constantly critical or even negative. Therefore, "high" had to be put in brackets. The number of lines of this table already shows that the evaluation of quasi-continuous traits is not simple but multidimensional. Evaluation depends greatly on the scientific question being analysed. For the determination of the affinities of a population in time and space, measurements are preferable; and for a small-scale population genetical question, discreta and blood groups might be preferable. Yet if we disregard such differentiation of investigational design, it must be concluded that discreta are not suited for most population analyses. They are disqualified, at the present time, by the lack of a standard for determination and by the poor state of knowledge regarding their genetic basis. Adapted from: R6sing, F. W. (1982). Discreta des menschlichen Skeletts--ein kritischer Uberblick. Homo 33, 100-125 (where the bibliography may be found).
Discreta of the Human Skeleton: a Critical Review
Abteilung Anthropologie und Wissenschaftsforsehung, Universitlit Ulm, Ulm, West Germany
Published results concerning, and unpublished experiments with discreta (discrete or quasi-continuous traits) suggest that analysis of such traits is plagued with serious difficulties, particularly a virtually unknown genetic background and the lack of a standard for their definition and determination. Thus, this trait complexappears to be unsuited for most populational investigations.
1. I n t r o d u c t i o n
The purposes of this paper are: (1) to give a general review of present knowledge regarding quasi-continuously variable traits (discreta/"epigenetic" traits/anatomical variants), and (2) to substantiate the wide spread doubts about the theoretical foundation of these traits, which are seldom formulated in papers but are practically always part of oral treatment of the topic. A review of this topic is appropriate at the present time, because a shift in orientation is evident in papers dealing with this theme. The period of large initial considerations has passed. The traits examined consist of: (1) variants of bone numbers and suture configurations, (2) numerical and shape variants of foramina, (3) hyperostotic (and hypoostotic) variants, (4) numerical and shape variants of teeth. This classification shows that discreta are heterogeneous. Their only common characteristic is their small size. For designation of this trait complex "quasi-continuous traits" is recommended, or as a short, and less precise, term "discreta". "Epigenetic traits" and "non-metric traits", however are inappropriate for several reasons. For example, the term "genetic" is often understood to be a characterizastion of these traits, but their genetic determination is largely unknown. Furthermore, if we trace back "epigenetic" to the epigenesis theory of Wolff (1759), then every trait complex which is generally measured or observed should be included. The trait names in this paper are in latin, following the latest proposal by I~lesnys & Pavilonis (1982). The present wide-spread interest in discreta stems mainly from a paper by Berry & Berry (1967). It must be stressed that this work is defective in most of the critieria of scientific quality which can be formulated (dogmatic genetical statements without material basis, lack of differentiation between traits and between animal species, criticism of other trait complexes without adequate knowledge of them, different or contradictory interpretation of the same results). Its value rests upon its stimulation of further research. 2. G e n e t i c s
The most important basic property of any trait in physical anthropology is its genetic determination. There are m a n y older papers which contain conclusions like: "determined by three loci", "one dominant autosomal gene", "high penetrance and expressivity" etc. These statements should be regarded as history, typical examples of a period in science in which genetics was totally restricted to simple categories. Journal of Human Evolution (1984) 13, 319-323
0047-2484/84/040319 + 05 $03.00/0
9 Academic Press Inc. (London) Limited
320
F.w. R6sINe
Today we may presume that discreta are determined by a large amount of hierarchically organized genetic information, just as in the case of measurements or traits reflecting shape. Thus, as in the case of these latter trait complexes, genetic determination may best be described by heritability measures. If we check the literature for precise heritability information on quasi-continuous traits, we find first that there is not even one publication on the whole trait system in humans. We find only information on single traits (e.g. Garn, 1966; Saunders & Popovich, 1978) and information on mice (Self& Leamy, 1978) and macaques (Cheverud & Buikstra, 1981). As a general conclusion, it must be stated that only a small minority of discreta is known genetically. More specifically: six to eight traits can be regarded as predominantly determined genetically, and two frequently used traits are predominantly non-genetic (foramen infraorbitale accessorium and foramen zygomaticofaciale accessorium). This is a very meagre level of knowledge in the face of the fact that the average number of traits employed in recent papers is 28 and that the number of traits determined in at least one single population in the last decade surpasses 120.
3. Correlations and Variability A thorough examination of the literature reveals only a few significant inter-trait correlations, but here again information is sparse and partly contradictory. Several studies conclude that there are few traits which exhibit significant sex differences and none which exhibits significant sex differences across several populations. Age variability is sufficiently known. For hyperostotic variants, age dependence is known to be high, or may be presumed to be high (e.g. Buikstra, 1972). All other traits are age-independent (e.g. Perizonius, 1979a). Asymmetry of bilateral traits is negligible, even if we take into account that different questions may be being asked (for side preference or for symmetry preference). Only one paper (Kellock & Parsons, 1970a) contains information on trait-specific variability between populations. In this study ten traits already account for 90% of the total variability among australoids. This topic should certainly be investigated further, as it at least gives an objective criterion for the selection of specific traits to be included in population analyses.
4. Methods According to the experience of the author of this paper, at least half of the 40 traits most commonly used are ill-defined in the literature. Particularly the description "extra-sutural" is far from being unequivocal, and it might even be suspected that it is basically impossible to define discontinuous manifestations of this characteristic. This means that frequencies by different workers are not comparable (see also Molto, 1979; Thoma, 1981). A direct check of the inter-observer error (Finnegan & Rubison, 1980) revealed devastatingly high deviations for several traits. This restricts the applicability of discreta to analyses of data by only one individual investigator. Thus, at the present time the methodology of quasi-continuous traits is in a developmental stage comparable to that of metric traits before the Frankfurt Verst~ndigung of the last century.
321
DISCRETA OF THE HUMAN SKELETON
5. Applications The majority of population comparisons published so far seems to yield meaningful results which are comparable to or supplement other knowledge about human populations. Yet one of the best papers in the field (Thoma, 1981) concludes that there is "nonsense variation" between races. In general, there is a tendency to find more meaningful results if the populations are more closely related to each other. This suggests that discreta might be better applicable to small-scale analyses (see also Brothwell, 1959, p. 93). Some population biological processes have ben analysed by means of discreta (e.g. Table 1
Familial differentiation of discreta in the Aswan necropoles Qubbet el Hawa and Elephantine. n-no. of variants, N-no. of individuals, %--relative frequency of variants, P . x 2 significance in % in comparison with total I, total I - o b s e r v a t i o n s on socially determinable and clearly dated individuals, total II--all observations. Both sexes and all ages pooled Total I n/N %
Total II n/N %
1 Sutura metopica 18/447 4'0 29/675 4"3 2 Foramen supraorbitale 77.5/441 17'6 115'5/667 17"3 3 Sulcus frontalis 96'5/441 11"9 133/664 20"0 4 0 s s a suturae coronalis 27 5/401 6"9 35/603 5'8 5 0 s bregmae 2/395 0-5 2/592 0-3 6 0 s s a suturae sagittalis 11/377 2"9 16/556 2'9 7 Foramen partietale absens 145/432 33"6 214/649 33"0 8 0 s lambdae 42/399 10'5 59/601 9'8 9 0 s incae 11/420 2"6 17/629 2-7 10 Ossa suturae lambdoideae 135/407 33'2 211'5/610 34"7 11 Os asterii 32/408 7-8 48/625 7-7 12 Os incisurae parietalis 39/406 9'6 58'5/623 9"4 13 Canalis condylaris abs. 99/389 25"4 146/589 24"8 14 Canalis hypoglossi acc. 70/398 17'6 107/605 17"8 15 Facies cond. bipartitus 0-5/394 0"1 0'5/601 0"1 16 Tuberculumpraecondylare 50'5/394 12'8 71"5/600 11"9 17 Foramen ovale incompl. 5.5/397 1"4 8"5/606 1-4 18 For.spinosum incompl. 58'5/393 14'9 84/598 14"0 19 Foramen Huschkei 37.5/415 9"0 53-5/628 8"5 20 For, mast, extrasuturae 139"5/398 35"1 219/608 3 6 - 0 21 Foramen mastoideum abs. 57.5/398 14"4 83-5/609 1 3 " 7 22 Torus acusticus 4/421 1'0 4/643 0"6 23 Os pterii 50/362 13"8 70"5/573 12"3 24 Sutura frontotemporalis 9/372 2"4 12/584 2"1 25 For. ethm. ant. extras. 52-5/245 21"4 82-5/381 21"7 26 For. ethm. post. absens 34'5/277 12'5 40/453 8"8 27 For. infraorbitale acc. 11.5/334 3"4 21"5/509 4"2 28 Torus palatinus 0/354 0'0 0/537 0'0 29 Toruis maxillaris 7.5/359 2"1 9/540 1"7 30 For. palatinum majus abs. 9/336 2'7 21'5/512 4"2 31 For. palat, minus absens 9/325 2"8 13"5/499 2"7 32 For. palat, minus acc, 181'5/322 56'4 25'7/496 51"8 33 For. zygom'faciale abs. 34.5/365 9"5 45"5/552 8"2 34 For. zygom'faciale acc. 194/366 53'0 304/552 55'1 35 M3 maxillae absens. 42/339 12-4 39-5/485 8-1 36 M3 mandibula abs. 23"5/260 9'0 39/370 10-5 37 Torus mandibularis 6.5/279 2"3 7"5/413 1"8 38 For. mentale accessorius 12/280 4'3 16'5/413 4'0
Grave 88 n/N %
P
1/62 1"6 13/62 21'0 9"5/62 13"7 1"5/56 2"7 t/54 1-9 1/54 1"9 15/59 25"4 6/56 10"7 1/59 1'7 205/58 35"3 2"5/59 4"2 3"5/60 5'8 10"5/51 20"6 8/54 14"8 0/54 0"0 6/55 10"9 0"5/54 0'9 7"5/53 14"2 11/59 18'6 2'27 t7"5/56 31-3 6"5/56 11'6 0/60 0'0 3"5/49 7"1 1/53 1"9 4/27 14'8 2/34 5'9 1/45 2"2 0/49 0"0 0/49 0"0 2"5/45 5'6 0-5/44 1"1 24/43 55"8 2"5/52 4"8 31/53 58"5 3-5/44 8-0 0"5/51 0"9 4"89 0/54 0"0 4/54 7"4
Grave 89 n/N % 2/35 3/33 12'5/33 4/32 0/32 0/36 17/35 2/34 1/33 13"5/36 6/35 7"5/34 10/32 9/32 0/33 15-5/33 1/33 8/33 3/34 14-5/32 4"5/32 2/34 2"5/29 1"5/30 5/22 9/24 0'5/26 0/30 0/31 0/30 3"5/29 13/28 3'5/30 17/30 2/31 3/17 1/18 1/18
5'7 9-1 37"9 12"5 0-0 0"0 48"6 5"9 3"0 37"5 17"1 22-1 31"3 28-1 0"0 47-0 3"0 24-2 8"8 45-3 14"1 5"9 8"6 5-0 22"7 37-5 1"9 0"0 0"0 0"0 12"1 46-4 11"7 56-7 6-4 17-6 5'6 5"6
P
3"53
2-32
0'00
1-98
0"08
0"93
322
v . w . R6SINO
migration/gene flow, isolation/fbunder effects and selection). A first example for the use of discreta to investigate social assortment or isolation is given in the original paper (R/Ssing,
1982). Under favorable conditions, individual relationships might be analysed by means of discreta. An example of markedly different familial occurrence of several traits is given in Table 1. Both Aswan necropoles belonged to the same settlement, but differ in the social status of the grave owners. Both are dated from the end of the 5th dynasty to the 12th dynasty ("total I" of Table 1) or the 26th dynasty ("total I I " ) . The table gives observations from two graves which are neighbors and closely related in size and quality. Family grave 88 has rather "normal" frequencies, whereas 89, despite the smaller group size, is untypical of this population. A further analysis might reveal such things as which individuals married into the family 89.
6. Conclusion I f we compare the properties of discreta to those of other skeletal traits we arrive at the following synopsis:
Information level Genetics, known simple determination genomerepresentation Trait intereorrelation Sex variation Age variation Comparable to living to other groups Method standardization determination problems Individual representation Determination time General esteem
Discreta
Measurements Shapetraits
Si:rology
Low Poorly Yes? High? Moderate? Low? Rare Low No Poorly No Yes High (Low) (High)
High Well No Moderate High High Yes Yes Yes Well Yes No Low Moderate High
Low Very well Yes Very high Low Very low No No Yes Poorly Yes No (Total) High Moderate
High Moderately No Moderate? High Moderate Yes Yes Yes Poorly No Yes High Higher Low
The majority of the statements in this table may be substantiated by theoretical arguments or literature; moreover, they are based on numerous personal communications from experts in this field. Several entries in this table demand further explanation. In the case of shape traits and serology, the degree of knowledge about the genetics is, of course, based only on studies of living groups. "Determination" means the relative part of trait variances determined by genetic information as oppposed to environmental influences. The line "comparable to other groups" condenses the number of groups already studied and published, which may be used for comparisons. "Individual representation" means, for example, that in the frequently occurring case of incomplete or fragmentary skeletons, measurements may not be taken but a greater number ofdiscreta and theoretically the ABO blood groups of every individual may be determined. The statement on "determination time" in the case of discreta had to be placed in brackets because the lack of standardization frequently creates time-consuming problems. General esteem for discreta seems very high only if we count
DISCRETA OF THE HUMAN SKELETON
323
published statements. Oral statements, however, are almost constantly critical or even negative. Therefore, "high" had to be put in brackets. The number of lines of this table already shows that the evaluation of quasi-continuous traits is not simple but multidimensional. Evaluation depends greatly on the scientific question being analysed. For the determination of the affinities of a population in time and space, measurements are preferable; and for a small-scale population genetical question, discreta and blood groups might be preferable. Yet if we disregard such differentiation of investigational design, it must be concluded that discreta are not suited for most population analyses. They are disqualified, at the present time, by the lack of a standard for determination and by the poor state of knowledge regarding their genetic basis. Adapted from: R6sing, F. W. (1982). Discreta des menschlichen Skeletts--ein kritischer Uberblick. Homo 33, 100-125 (where the bibliography may be found).