Barış Özener

Fluctuating and directional asymmetry in young human males: Effect of heavy working condition and socioeconomic status†

Many adverse environmental and genetic factors can affect stability of development during human growth. Although the level of fluctuating asymmetry (FA) may be influenced by environmental and genetic stress encountered during this period, directional asymmetry (DA) is largely attributable to differential mechanical loading during bone growth, for example, handedness. I assessed the effects of heavy working conditions and socioeconomic conditions on asymmetry levels in three groups of young human males: 1) individuals employed in the heavy industry sector (n = 104, mean age = 18.48 +/- 0.61 years), 2) individuals who had the same socioeconomic status as the laborers (n = 102, mean age = 18.39 +/- 0.58 years) but were not laborers, and 3) nonlaborers from the higher socioeconomic levels of society (n = 103, mean age = 18.43 +/- 0.67). For all subjects, hand length, hand width, elbow width, wrist width, knee width, ankle width, foot length, foot width, ear length, and ear width were measured. All measurements of the upper extremities in the labor group appeared to exhibit DA; in the other two groups only hand measurements exhibited DA. According to analysis of FA, subjects living in poor conditions exhibited more FA than their nonlaborer peers living in better conditions. In addition, biomechanical pressures due to heavy working conditions of the labor group appeared to cause increased DA in the upper extremities: DA increased with an increase in the number of years working.

Facial soft tissue thickness in individuals with different occlusion patterns in adult Turkish subjects

Knowledge of variation in facial soft tissue thickness is important for forensic anthropologists, dentists, and plastic surgeons. Forensic anthropologists use such information as a guide in facial reconstruction and superimposition methods. The purpose of this study was to measure facial tissue thicknesses of adult males and females of Turkish origin across different types of occlusion, and to compare the results with each other and with values obtained for other populations. The study was conducted on 200 healthy individuals. The analysis of facial tissue thickness included 20 landmarks (10 dentoskeletal and 10 soft tissue) and 10 linear variables. Sex-based variation in facial tissue thickness was noted. The highest soft tissue thickness values were observed in the group with Class III occlusion type at Sn-A point for both the females (16.9, SD=2.4) and the males (17.8, SD=3.3). In the Class I group, the highest tissue depth was observed at Sn-A point (15.3, SD=2.1) in females, and at Li-Id point (17.1, SD=1.9) in males. In the Class II group, contrary to the findings for Class I, the highest soft tissue depth was at Li-Id point (16.0, SD=1.4) in females, and at Sn-A point (18.1, SD=2.6) in males. In conclusion, facial tissue thickness varied in adults depending on the sex and on the type of occlusion.

Effect of inbreeding depression on growth and fluctuating asymmetry in Turkish young males.

This study sought to examine the effects of inbreeding on physical development and fluctuating asymmetry (FA). A total 144 male high-school students (mean age = 18.11 +/- 0.52) whose parents are first cousins (F = 0.125) of low-socioeconomic status and 146 male students (mean age = 18.08 +/- 0.54) from the same school who do not have any consanguineous parents (F = 0) were observed in Ankara. In addition to the weight and height measurements of the individuals, eight bilateral traits (hand width, elbow width, wrist width, knee width, ankle width, foot width, ear length, and ear width) were measured. Whereas the inbred group has lower values in terms of weight and height, the difference in body mass index between the groups is not significant. Although the inbred group is more asymmetric in terms of the observed bilateral traits, the differences are below the significance level. However, the composite FA index shows that the inbred group is more asymmetric and the difference is significant (P < 0.05). Inbreeding depression has a negative effect on weight and height development, and a negative effect on developmental stability.

Brief communication: Facial fluctuating asymmetry as a marker of sex differences of the response to phenotypic stresses.

Fluctuating asymmetry (FA) is thought to increase as a result of environmental perturbations during development. A number of studies involving measures of health and developmental stability other than FA have discussed the presumed increased buffering in females relative to males. But, there is little evidence in the literature on FA to support this hypothesis. This research was conducted to determine the level of difference in terms of facial FA between sexes under different environmental conditions. Group 1 included final year students from three high schools in Yenimahalle, a slum district of Ankara (males: N = 163, mean age = 17.55, sd = 0.50; females: N = 141, mean age = 17.48, sd = 0.38). Group 2 included students with higher socioeconomic background and was composed of final year students from three different private schools located in Cankaya (N = 171, mean age = 17.44, sd = 0.26; females: N = 152, mean age = 17.38, sd = 0.31). Digital images were used to assess the degree of facial asymmetry as measured from eight paired traits and calculated as a composite score. The study shows that the male students had higher facial asymmetry than the female students. However, the present difference reaches a significant level in the low-socioeconomic status group. As a result, it could be inferred that differences in developmental stability between sexes might emerge under stressful conditions.

Growth and fluctuating asymmetry of human newborns: Influence of inbreeding and parental education

Historically, medical concerns about the deleterious effects of closely inbred marriages have focused on the risk posed by recessive Mendelian disease, with much less attention to developmental instability. We studied the effects of inbreeding (first-cousin marriage) on growth and fluctuating asymmetry of 200 full-term infants (101 inbred and 99 outbred) whose parents were of similar socioeconomic status in Sivas Province, Turkey. In addition to differences in their mean inbreeding coefficients (f = 1/16 for first cousins and f < 1/1,024 for unrelated parents), the consanguineous parents were less well educated (3 years, on average for both husbands and wives). We measured weight, height, head circumference, and chest circumference of the newborns, as well as four bilateral traits (ear width, ear length, and second and fourth digit lengths). After taking education into account, none of the measures of size (weight, height, head circumference, and chest circumference) and fluctuating asymmetry differed between the inbred and outbred groups. Male children of well-educated parents, however, were larger and had less fluctuating asymmetry. Female children of well-educated parents weighed more than those of less well-educated parents, but were otherwise indistinguishable for height, head circumference, chest circumference, and fluctuating asymmetry. We conclude that inbreeding depression causes neither an increase in fluctuating asymmetry of full-term newborns, nor a decrease in body size. Unmeasured variables correlated with education appear to have an effect on fluctuating asymmetry and size of male children and only a weak effect on size (weight) of female children.

Relationship between shortness of final body height and fluctuating asymmetry in Turkish young males

Background: Body height is a versatile bio-indicator in that it reflects the quality of physical development. Fluctuating asymmetry, on the other hand, refers to small random deviations from perfect symmetry in bilaterally paired structures and is believed to reflect the ability of an organism to cope with genetic and environmental stresses during its development. Aim: This study sought to investigate the relationship between body height and fluctuating asymmetry in young adult males who display different height-development structures. Subject and methods: Height and eight bilateral non-facial traits were measured in a sample of 320 young male individuals from different socioeconomic backgrounds who display differences in height. Z-scores of each individual were calculated based on the age-range values indicated in the Center for Disease Controls (CDC) 2000 growth data of the US. Results: The five measurements demonstrating fluctuating asymmetry indicate that there is a significant increase in fluctuating asymmetry that parallels the decrease in body height. Developmental stability increases with the increasing body height. Conclusion: This finding implies that the stresses causing slower growth in body height might have negative effects also on fluctuating asymmetry.

Fluctuating Asymmetry of Human Populations: A Review

Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population’s state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The most widely used bilateral traits include skeletal, dental, and facial dimensions; dermatoglyphic patterns and ridge counts; and facial shape. Each trait has its advantages and disadvantages, but results are most robust when multiple traits are combined into a composite index of fluctuating asymmetry (CFA). Both environmental (diet, climate, toxins) and genetic (aneuploidy, heterozygosity, inbreeding) stressors have been linked to population-level variation in fluctuating asymmetry. In general, these stressors increase average fluctuating asymmetry. Nevertheless, there have been many conflicting results, in part because (1) fluctuating asymmetry is a weak signal in a sea of noise; and (2) studies of human fluctuating asymmetry have not always followed best practices. The most serious concerns are insensitive asymmetry indices (correlation coefficient and coefficient of indetermination), inappropriate size scaling, unrecognized mixture distributions, inappropriate corrections for directional asymmetry, failure to use composite indices, and inattention to measurement error. Consequently, it is often difficult (or impossible) to compare results across traits, and across studies.

Extreme behavioral lateralization and the remodeling of the distal humerus

Objectives: The effects of extreme behavioral lateralization (i.e., extreme handedness) on the epicondylar breadth are poorly understood. This study was conducted in order to determine the effects of high levels of right‐ and left‐handedness on epicondyle of the humerus.

Inbreeding is associated with lower 2D: 4D digit ratio.

While consanguineous marriage has been shown to result in a small increase in risk of recessive Mendelian disorders among offspring, far less research has been conducted on the effects of inbreeding on complex traits. These effects, thought to result from increased developmental instability due to loss of heterozygosity, are expected to be found more pervasively than rare recessive Mendelian traits and are expected to result in increased developmental noise. Here, we test for a direct effect of inbreeding on 2D : 4D, a putative indicator of prenatal hormonal environment.