Non-metric cranial traits: Sex difference and age dependence

Absence of association with age and/or sex in the case of discrete traits was hypothesized by Berry & Berry (1967). The important implication that skeletal material too fragmentary for sex and age determination may also be used in discrete-trait-studies stimulated us to test this hypothesis for 49 discrete traits in 254 Amsterdam crania of known age and sex. The results were compared with those of other such studies of European skulls. No significant deviation from the hypothesis was found as far as age dependence is concerned while sex difference did occur for some traits. At the same time Corruccini's (1974) conclusion that the hypothesis fails when tested in the Terry collection was found to result largely from the fact that right and left manifestations of lateral traits were treated as being independent. The possibility of including skeletal material too fragmentary for sex and age determination in future discrete-trait-studies is still open for discussion.     

Study on long bones: variation in angular traits with sex, age, and laterality

The biological problems considered in this study are sexual dimorphism in angular osteometric traits, changes in these traits with aging and their bilateral asymmetry in the same individual. The sample comprises the right and left long bones of 200 skeletons (100 males and 100 females) of Sardinian adults (Frasetto collection) for whom the sex and age at death are known. As concerns the sexual dimorphism, some angular traits of upper limb (joint axis angle of the ulna in particular) and the lower limb (condylo-diaphyseal angle of the femur and retroversion angle of the tibia) are significantly different between males and females. Torsion angles of long bones (especially the femur) were found to change with age. In sides comparison revealed a clear right-left asymmetry in our sample. The asymmetry, sexual dimorphism and changes with age are discussed in relation to varying stresses of different living activities. Our data indicate that the angular traits of long bones could be very informative in biomechanical interpretations of human activities based on skeletal remains.     

Discontinuous traits of the skull: variations on sex, age, laterality

This paper discusses some problems relating to the study and the utilization of discontinuous traits in anthropology. The importance of sex, age and laterality in the manifestation of these traits is discussed on the basis of investigations on a numerous skeletal sample of Siena (Tuscany, Italy) and on data from literature. It is pointed out that sides and sexes should be considered separately. The age of adult subjects seems to be insignificant as the incidence of these traits is concerned.     

Timing and genetic rapport between growth in skeletal maturity and height around puberty: similarities and differences between girls and boys.

We have analyzed longitudinal twin data by using a multivariate normal model to identify and quantify genetic effects over time on two main aspects of growth, height and skeletal maturity. The largest genetic contribution to the variance in both height and skeletal maturity coincided with the respective ages of peak growth velocity. The highest genetic covariance between these two traits coincided with the age of greatest acceleration of growth in height. These findings imply the existence of regulatory or structural genes that influence growth in both height and skeletal maturity. We also found sex differences in the rapport between velocities for height and skeletal maturity. These are consistent with a predominant role of estrogen in accelerating skeletal maturation in females, and the existence of additional mechanisms in males which may promote growth in height independently of the effects of gonadal sex steroids.     

Maximum-likelihood variance components analysis of heritabilities of cranial nonmetric traits

Nonmetric traits of the cranium are often used to support hypotheses of the history and divergence of human populations. These studies rely on the assumption that nonmetric traits are heritable, yet few skeletal series exist with associated pedigree information that allow for the calculation of additive genetic variance, or heritability. In addition, traits for which heritabilities have been published represent dichotomous present/absent forms instead of the range of expression that can be observed for many nonmetric characters. In the present study I use a maximum-likelihood variance components analysis to calculate univariate narrow-sense heritability estimates on the skeletal series from Hallstatt, Austria, for 9 sutural bones, 27 multilevel traits, and dichotomized present/absent forms for 19 of these multilevel characters. Most of the trait heritabilities do not differ significantly from a model of h2 = 0, and they have large standard errors. In a heuristic comparison of multilevel versus dichotomous trait forms, most of the nonmetric characters showed no differences in heritability between the two methods used for parsing the phenotypic variation, although where differences were noted, the presence-absence version had higher heritabilities. These results have implications not only for the use of particular nonmetric traits in population studies but also for the practice of character dichotomization in data collection.     

Walnut creek massacre: Identification and analysis

The purpose of this study is to add to our understanding of skeletal material from the American pioneer period. Eight White and two Negro skeletons were washed out of their graves during flood conditions of 1973, but the recovery and subsequent storage of this material permitted commingling, and identification of the individual skeletons had to be undertaken before the material could be analyzed. Variation in age, sex, race, metric, non-metric traits and condition of the bone was considered prior to the analysis of the material. When these methods failed, ultra-violet fluorescence of the material and the matching of individual bones with colour slides taken at the time of the excavation were employed. Identification of all bones for the ten skeletons was impossible. However, on the basis of non-metric trait variation a father and son pairing is tentatively identified. Analysis of this material shows the early pioneer to have been a rather tall and robust individual displaying little bone pathology, but advanced pathology in the dental tissue and alveolar region. Historical records pertinent to this massacre validate the identification of sex, race, and age for these individuals.     

Anatomical, physiological, and epidemiological correlates of the aging process: a confirmation of multifactorial age determination in the Libben skeletal population

Paleodemographic analyses based on estimates of skeletal age at death consistently report high levels of young adult mortality with few individuals living in excess of 50 years. Critics assert these data indicate systematic underaging of adults and justifiably remark that criteria for estimating skeletal age at death may be unreliable, age determinations are too frequently based on one or two criteria alone, and adult paleodemographic age profiles often mimic the age distribution of the modern population from which an age indicator's standards were originally derived. This study reports a series of tests based on well-documented biological aging phenomena that can be used to investigate potential effects of systematic underaging in adults, assuming the skeletal population is of sufficient size to permit such tests. These include patterns of third decade sternal clavicular epiphyseal fusion, multiple age and sex criteria associated with cortical bone dynamics, and fractures known to occur throughout the entire adult ages range. These phenomena are examined here for the Libben site skeletal population where adult age at death was determined by the multifactorial summary age technique. None of the biological criteria reported here were used in the Libben summary age analysis and thus serve as an independent test of accuracy in age determination. In addition, the summary age method has recently been applied to a series of modern skeletons of known age (Todd samples 1 and 2). Age standards for criteria employed with Libben and Todd 1 were identical. Since Todd 1 displayed underaging in older adults, a second Libben age distribution adjusted for Todd 1 bias was generated for comparison. A third Libben adult survivorship profile based on a Coale and Demeny West level 3 mortality experience, considered by some to be a more realistic model for skeletal populations, was produced for comparison. For all criteria examined, original Libben summary ages provided superior concordance with known patterns of biological aging in human populations. While Libben ages adjusted for Todd 1 bias were slightly better in the third decade, both Todd 1 adjusted and Coale and Demeny West level 3 age distributions produced unrealistic patterns of biological aging for individuals greater than 35 years. Implications of these results are discussed.     

Long-lasting fitness consequences of prenatal sex ratio in a viviparous lizard

Maternal effects and early environmental conditions are important in shaping offspring developmental trajectories. For example, in laboratory mammals, the sex ratio during gestation has been shown to influence fitness-related traits via hormonal interaction between fetuses. Such effects have the potential to shape, or constrain, many important aspects of the organism's life, but their generality and importance in natural populations remain unknown. Using long-term data in a viviparous lizard, Lacerta vivipara, we investigated the relationship between prenatal sex ratio and offspring growth, survival, and reproductive traits as adults. Our results show that females from male-biased clutches grow faster, mature earlier, but have lower fecundity than females from female-biased clutches. Furthermore, male reproduction was also affected by the sex ratio during embryonic development, with males from male-biased clutches being more likely to successfully reproduce at age one than males from female-biased clutches. Thus, the sex ratio experienced during gestation can have profound and long-lasting effects on fitness in natural populations of viviparous animals, with important implications for life-history evolution and sex allocation.     

Pleiotropic patterns of quantitative trait loci for 70 murine skeletal traits

Quantitative trait locus (QTL) studies of a skeletal trait or a few related skeletal components are becoming commonplace, but as yet there has been no investigation of pleiotropic patterns throughout the skeleton. We present a comprehensive survey of pleiotropic patterns affecting mouse skeletal morphology in an intercross of LG/J and SM/J inbred strains (N = 1040), using QTL analysis on 70 skeletal traits. We identify 798 single-trait QTL, coalescing to 105 loci that affect on average 7-8 traits each. The number of traits affected per locus ranges from only 1 trait to 30 traits. Individual traits average 11 QTL each, ranging from 4 to 20. Skeletal traits are affected by many, small-effect loci. Significant additive genotypic values average 0.23 standard deviation (SD) units. Fifty percent of loci show codominance with heterozygotes having intermediate phenotypic values. When dominance does occur, the LG/J allele tends to be dominant to the SM/J allele (30% vs. 8%). Over- and underdominance are relatively rare (12%). Approximately one-fifth of QTL are sex specific, including many for pelvic traits. Evaluating the pleiotropic relationships of skeletal traits is important in understanding the role of genetic variation in the growth and development of the skeleton.     

Quantitative trait loci for bone traits segregating independently of those for growth in an F2 broiler x layer cross

An F2 broiler-layer cross was phenotyped for 18 skeletal traits at 6, 7 and 9 weeks of age and genotyped with 120 microsatellite markers. Interval mapping identified 61 suggestive and significant QTL on 16 of the 25 linkage groups for 16 traits. Thirty-six additional QTL were identified when the assumption that QTL were fixed in the grandparent lines was relaxed. QTL with large effects on the lengths of the tarsometatarsus, tibia and femur, and the weights of the tibia and femur were identified on GGA4 between 217 and 249 cM. Six QTL for skeletal traits were identified that did not co-locate with genome wide significant QTL for body weight and two body weight QTL did not coincide with skeletal trait QTL. Significant evidence of imprinting was found in ten of the QTL and QTL x sex interactions were identified for 22 traits. Six alleles from the broiler line for weight- and size-related skeletal QTL were positive. Negative alleles for bone quality traits such as tibial dyschondroplasia, leg bowing and tibia twisting generally originated from the layer line suggesting that the allele inherited from the broiler is more protective than the allele originating from the layer.     

Host plant effects on the behavioural phenotype of a Chrysomelid

1. The food plant quality influences feeding preferences and various life history traits of herbivorous insects. However, the effects of different host plant qualities on the behavioural phenotype have rarely been studied in behavioural ecology, especially in a pest‐crop‐framework. 2. Behavioural phenotypes of insects may not only be affected by external environmental factors, such as the host plant quality but are also shaped by internal factors, such as the sex and the age of individuals. 3. To study host plant effects on behavioural phenotypes, we reared mustard leaf beetles (Phaedon cochleariae Fabricius) either on their natural host watercress or on the crop cabbage, on which this beetle can be a pest. The behavioural phenotype was characterised twice in the adult lifetime by measuring six behavioural traits tested in distinct contexts. 4. Depending on the context, different behavioural traits were specifically affected by the host plant, the sex and/or the age. Beetles fed on cabbage became more active with age. Furthermore, the boldness tested in an unprotected environment context was influenced by the host, with beetles fed on cabbage being bolder, whereas the boldness in a hiding or predator attack context was affected by the age and/or the interaction of host plant × sex. 5. In conclusion, beetles fed on the crop cabbage develop a different behavioural phenotype compared to beetles fed on watercress. Previous results showed that beetles reared on cabbage have a higher reproductive output. Thus, beetles fed on the crop potentially express a faster pace‐of‐life.     

Testing the phenotypic gambit: phenotypic, genetic and environmental correlations of colour

Evolutionary theory is primarily concerned with genetic processes, yet empirical testing of this theory often involves data collected on phenotypes. To make this tenable, the implicit assumption is often made that phenotypic patterns are good predictors of genetic patterns; an assumption that coined the phenotypic gambit. Although this assumption has been validated for traits with high heritability, such as morphology, its generality for traits with low heritabilities, such as life-history and behavioural traits, remains controversial. Using a large-scale cross-fostering experiment, we were able to measure genetic, common environmental and phenotypic correlations between four colour traits and two skeletal traits in a wild population of passerine birds, the blue tit (Parus caeruleus). Colour traits had little heritable variation but common environment effects were found to be important; skeletal traits showed the opposite pattern. Positive correlations because of a shared natal environment were found between all traits, obscuring negative genetic correlations between some colour and skeletal traits. Consequently, phenotypic patterns were poor surrogates for genetic patterns and we suggest that this may be common if trade-offs or substantial parental effects exist. For this group of traits, the phenotypic gambit cannot be made and we suggest caution when inferring genetic patterns from phenotypic data, especially for behavioural and life-history traits.     

SEX RATIO VARIATION IN A PARASITIC WASP II. DIALLEL CROSS

Sex ratio has been studied from many theoretical and empirical perspectives, but a general assumption in sex ratio research is that changes in sex ratio occur because of selection on sex ratio itself. I carried out a quantitative genetic experiment—a diallel cross among three strains—on a parasitic wasp, Muscidifurax raptor (Hymenoptera: Pteromalidae), to measure genetic variation for sex ratio. I also tested whether sex ratio may change as a consequence of selection on other life-history traits by estimating genetic covariances between sex ratio, fecundity, longevity, and development time. Most of the variation among strains could be accounted for by a maternal effect, likely caused by a microsporidian parasite that was transmitted through the West Germany (WG) strain. Genetic variation was small by comparison, but almost all traits were affected by dominance. The only significant additive genetic effect was for fecundity early in life. Upon crossing, all traits displayed heterosis: more female-biased sex ratio, greater fecundity, longer life, and faster development time. All life-history traits were correlated phenotypically, but the correlations were mainly the result of decreased performance in crosses with the WG strain that carried the microsporidian parasite. Dominance genetic correlations were also found between sex ratio, fecundity, and longevity. How the correlation between sex ratio and other life-history traits would affect sex ratio evolution depends upon the frequencies of sex-ratio genotypes within a population as well as the signs of the correlations, because sex ratio is under frequency-dependent selection whereas other traits are generally under directional selection. Although the results from crosses among laboratory populations should be approached with caution, the inbreeding depression (the difference between inbred and outcrossed progeny) found in M. raptor implies that the evolution of a female-biased sex ratio could be affected by selection for inbreeding avoidance.     

Evaluation of morphological sex determinations by molecular analyses

The study presents an evaluation of morphological sex determinations of adult skeletal individuals based on traits of the ossa coxae and the cranium. The evaluation criterion was genetic analysis of the amelogenine gene, which represents parts of the X- and the Y-chromosome (Mannucci et al. 1994). The study was carried out on 33 human skeletons from an early modern burial site in Lower Saxony. In this skeletal series, 88% of the morphological sex determinations matched the genetic sex. The percentage of matches was further improved, if only those morphological determinations were taken into account that were classified as unambiguous by a self-evaluation. In the reverse case, a significant number of non-matching determinations (33%) resulted from those cases in which a sex determination still seemed possible but was classified as "ambiguous" in the self-evaluation. At least within this skeletal series, no clear connection could be detected between the number of matching results and the presence or absence of the ossa coxae. This might be due to a strong cranial dimorphism within this particular skeletal series.     

Age determination on long bones in a skeletal subadults sample (b-12 years)

The skeletal age on the basis of the diaphyseal length of long bones was assessed. To this aim a sample of subadults skeleton, dated to last century, coming from the cemetery of Bologna was studied. The sample is composed by 79 males and 70 females between 0 and 12 years, whose chronological age and sex are known. Some information can be obtained by the means, standard deviation and graphs of the specimens grouped in age classes. The comparison with other studies confirms the interest of using standards based on direct measurements on long bones of known age and similar to the skeletal populations under study.     

Factors influencing back strength and the changes due to age of the oraon agricultural labourers of jalpaiguri district, west bengal

Muscle strength is a major component of successful performance in almost every activity of daily living and it is critical to health and well-being. Anthropometric, blood pressure and strength measurements were taken from Oraon agricultural labourers of Jalpaiguri district of West Bengal. The data were analyzed to find out the differences between high and low back strength groups of both sexes in different traits of the parameters mentioned above. Secondly, identifying the peak age of muscle strength in both sex and the declining ages. Thirdly, the influencing factors which, affect the back strength. The results show that high back strength groups have higher mean values of most of the anthropometric traits compared to low back strength groups and the differences are significant in case of males, but females show significant differences in few traits. Blood pressures are relatively low in high back strength groups compared to low back strength groups in both sexes. The peak age for higher back strength seems to be within the age of 24 years for males and 20 years for females. The predictive variables for males were found to be grip strength and subscapular skinfold thickness, but females show grip strength, BMI, biceps girth, bicondylar diameter of humerus. The differences in influencing factors between males and females have been sorted out from sociocultural practice of the population.     

Associations between the rates of maturation of the bones of the hand-wrist

Skeletal maturation rates for the age interval 3 to 13 years were analyzed using bone-specific assessments (Greulich-Pyle) of serial radiographs of 40 children. The mean rates of skeletal maturation resembled those of the population from which the atlas standards had been derived. There was a linear trend of skeletal age against chronological age for most bones in each sex. Regression lines were fitted to these data and the b values of the regression lines were calculated. Communality indices were calculated from an intercorrelation matrix of these b values. There was a statistically significant rank order correlation between the sexes in the communality indices. They tended to be higher in the girls than in the boys and were relatively low for the radius, ulna and carpals. Communality indices within groups of bones were high in all rows, especially the metacarpals, but in each sex they were comparatively low in the first ray (metacarpal plus the phalanges of the corresponding digit) and in the fifth ray of the boys. Neighborhood effects on the levels of association of maturation rates were present, particularly in the carpus, but marginal effects were not noted.     

Females better face senescence in the wandering albatross

Sex differences in lifespan and aging are widespread among animals. Since investment in current reproduction can have consequences on other life-history traits, the sex with the highest cost of breeding is expected to suffer from an earlier and/or stronger senescence. This has been demonstrated in polygynous species that are highly dimorphic. However in monogamous species where parental investment is similar between sexes, sex-specific differences in aging patterns of life-history traits are expected to be attenuated. Here, we examined sex and age influences on demographic traits in a very long-lived and sexually dimorphic monogamous species, the wandering albatross (Diomedea exulans). We modelled within the same model framework sex-dependent variations in aging for an array of five life-history traits: adult survival, probability of returning to the breeding colony, probability of breeding and two measures of breeding success (hatching and fledging). We show that life-history traits presented contrasted aging patterns according to sex whereas traits were all similar at young ages. Both sexes exhibited actuarial and reproductive senescence, but, as the decrease in breeding success remained similar for males and females, the survival and breeding probabilities of males were significantly more affected than females. We discuss our results in the light of the costs associated to reproduction, age-related pairing and a biased operational sex-ratio in the population leading to a pool of non-breeders of potentially lower quality and therefore more subject to death or breeding abstention. For a monogamous species with similar parental roles, the patterns observed were surprising and when placed in a gradient of observed age/sex-related variations in life-history traits, wandering albatrosses were intermediate between highly dimorphic polygynous and most monogamous species.     

Genetic parameters estimation for preweaning traits and their relationship with reproductive,productive and morphological traits in alpaca

The aim of this study was to estimate the genetic parameters for preweaning traits and their relationship with reproductive, productive and morphological traits in alpacas. The data were collected from 2001 to 2015 in the Pacomarca experimental farm. The data set contained data from 4330 females and 3788 males corresponding to 6396 and 1722 animals for Huacaya and Suri variants, respectively. The number of records for Huacaya and Suri variants were 5494 and 1461 for birth weight (BW), 5429 and 1431 for birth withers height (BH), 3320 and 896 for both weaning weight (WW) and average daily gain (DG) from birth to weaning, 3317 and 896 for weaning withers height (WH), and 5514 and 1474 for survival to weaning. The reproductive traits analyzed were age at first calving and calving interval. The fiber traits were fiber diameter (FD), standard deviation of FD (SD), comfort factor and coefficient of variation of FD and the morphological traits studied were density, crimp in Huacaya and lock structure in Suri, head, coverage and balance. Regarding preweaning traits, model of analysis included additive, maternal and residual random effects for all traits, with sex, coat color, number of calving, month–year and contemporary group as systematic effects, and age at weaning as linear covariate for WW and WH. The most relevant direct heritabilities for Huacaya and Suri were 0.50 and 0.34 for WW, 0.36 and 0.66 for WH, 0.45 and 0.20 for DG, respectively. Maternal heritabilities were 0.25 and 0.38 for BW, 0.18 and 0.32 for BH, 0.29 and 0.39 for WW, 0.19 and 0.26 for WH, 0.27 and 0.36 for DG, respectively. Direct genetic correlations within preweaning traits were high and favorable and lower between direct and maternal genetic effects. The genetic correlations of preweaning traits with fiber traits were moderate and unfavorable. With morphological traits they were high and positive for Suri but not for Huacaya and favorable for direct genetic effect but unfavorable for maternal genetic effect with reproductive traits. If the selection objective was meat production, the selection would have to be based on the direct genetic effect for WW but not on the maternal genetic effect that has been shown to have less relevance. Other weaning traits such as WH or DG would be indirectly selected.