A new perspective on fluctuating odontometric asymmetry in South African Negroes

The mandibular molar pit-tubercle (MMPT) dental nonmetric trait: Comprehensive analysis of a large sample

Dental nonmetric traits are quasicontinous variables, mostly of genetic origin. Thus, sets of such traits allow biological distance estimation between samples. Mandibular molar pit-tubercle (MMPT) is a buccal trait defined by Weets (2009) in Irish samples. This study aims to analyze (a) trait frequencies, (b) grade definitions, (c) intraobserver error, (d) sexual dimorphism, (e) asymmetry, and (f) trait associations for MMPT in a Portuguese sample. The first (LM1), second (LM2) and third (LM3) lower molars of 600 identified individuals from the Coimbra collections were scored for MMPT in three scoring sessions. Intraobserver error, bilateral asymmetry and trait correlations were tested using Kendall's τ-b, while sexual dimorphism was verified using Pearson's χ². Frequencies (LM1: 2.1%; LM2: 3.5%; LM3: 30.3%) were similar to previous reports. However, a new free apex cusp form (grade 3+) was detected. Considering three scoring sessions, intraobserver precision was above 85%, and correlation coefficients between observations were positive and moderate to very strong (0.291<τ-b<0.835). Intrasample variation was low, since only LM3 showed sexual dimorphism (female: 30.2%; males: 16.2%; χ²=15.512; p<0.001; df=1; n=556) and large asymmetry (27.1%). There were no strong (τ-b>0.3) intertrait associations involving MMPT. MMPT shows low trait presence, sexual dimorphism and asymmetry in stable teeth (LM1 and LM2). Intraobserver precision is high, so scoring should be reliable, although a plaque and better threshold grade definition is needed. After further research on non-European samples, MMPT can be useful in biodistance research.

Finger ridge-count asymmetry and diversity in Andean Indians and interpopulation comparisons

A separate analysis of ulnar and radial finger ridge-counts, obtained from 115 Aymara Indians (55 males and 60 females) of northern Chile, was performed. From these variables, directional asymmetry, fluctuating asymmetry, indices of bilateral asymmetry (square root of A2), and intraindividual diversity (s/square root of 5) were calculated for each sex. The results show that most bimanual differences for the ridge-counts are not statistically significant in the Aymara, except for radial counts in female first and second fingers (right hand means are larger), while most ulnar-radial differences are highly significant in both sexes (radial values exceed ulnar ones). Most sex differences do not reach statistical significance, although males have more ridge-counts, lower directional asymmetry, somewhat lower fluctuating asymmetry, and lower indices of asymmetry and diversity than females. As fluctuating asymmetry is not larger in males, the dermatoglyphic findings do not indicate support for the hypothesis that males are less canalized than females. In accordance with the findings of other authors, interpopulation comparisons in the indices of asymmetry and diversity show ethnic differences. Both indices tend to be low in samples of African ancestry, high in samples of European origin, and intermediate in the Aymara, while Indian groups are characterized by high asymmetry and low diversity values. Moreover, the data reveal a geographical trend in that asymmetry and diversity values tend to decrease from the northern to the southern hemisphere in populations of Europe, the Middle East, and Africa, thus indicating greater ridge-count variability and heterogeneity among fingers in northern populations. It is assumed that this gradient primarily reflects different degrees of miscegenation and heterozygosity.

Variables affecting dental fluctuating asymmetry in human isolates

The aims of the present study are to 1) determine and describe levels of dental fluctuating asymmetry (FA) in a highly endogamous human group; 2) evaluate the effects of various FA measures on perceived FA levels and their interrelationships; 3) study the connections between dental variables (tooth size, class, position, type, location and dimension) and FA levels; and 4) estimate the interrelationships between dental FA measures. The study was carried out on 242 Bedouin boys aged 5 to 14 years. The results demonstrate that the main variables influencing dental FA levels within this population are tooth class (incisors, canine, premolars, molars) and position (mesial, distal) and that the interaction between the two is significant. When sample sizes are large enough and individual measures are needed for the statistical analysis, the use of a computational method based on absolute values is legitimate. Clear relationships between some FA dental traits are discerned through principal-components analysis.