Assessing non-metric skeleton characters as a morphological tool

Study of non-metric characters of the skull to determine the epigenetic variability in populations of the European wildcat (Felis silvestris silvestris) and domestic cats (Felis catus)

We studied the variability of non-metric cranial traits, mainly foramina, of European wildcats (Felis silvestris silvestris) and domestic cats (Felis catus) from Germany based on 28 non-metric traits in 211 skulls. The domestic cats were grouped together as a statistical population. The wildcats were divided into two populations: Harz and Hesse, which were further subdivided, based on traffic infrastructure, natural landscape, and in the Harz, on time period. Epigenetic variability, epigenetic distance and the fluctuating asymmetry were calculated to assess genetic variability, possible depressions and population stability. The epigenetic variability Iev of the wildcat groups ranged from 0.27 (Hesse II) to 0.40 (Harz I). The difference in Iev between all specimens from Harz and Hesse respectively was less (Iev = 0.37 Harz and 0.31 Hesse). Compared to other studies these values are not assumed to indicate genetic depression. The epigenetic distance between the wildcat samples is 0.0774 overall, and in each case higher between sub-groups of the Harz and Hesse than between groups within these regions, respectively. The significant epigenetic distance between Harz and Hesse might indicate—at least past formerly—restricted connectivity between these regions. The fluctuating asymmetry for wildcats in total is 11.74% and in the sub-groups it ranges from 8.47 to 16.14%. These values are below 20% are at the lower range known from populations of other mammal species. The use of fluctuating asymmetry had also been discussed critically in its usefulness to assess viability of populations.

A Parametric Bootstrap for the Mean Measure of Divergence

For more than 50 years the Mean Measure of Divergence (MMD) has been one of the most prominent tools used in anthropology for the study of non-metric traits. However, one of the problems, in anthropology including palaeoanthropology (more often there), is the lack of big enough samples or the existence of samples without sufficiently measured traits. Since 1969, with the advent of bootstrapping techniques, this issue has been tackled successfully in many different ways. Here, we present a parametric bootstrap technique based on the fact that the transformed θ, obtained from the Anscombe transformation to stabilize the variance, nearly follows a normal distribution with standard deviation $\sigma = 1 / \sqrt{N + 1/2}$σ=1/N+1/2, where N is the size of the measured trait. When the probabilistic distribution is known, parametric procedures offer more powerful results than non-parametric ones. We profit from knowing the probabilistic distribution of θ to develop a parametric bootstrapping method. We explain it carefully with mathematical support. We give examples, both with artificial data and with real ones. Our results show that this parametric bootstrap procedure is a powerful tool to study samples with scarcity of data.

Sex and age related non-metric variation of the human sternum in a Northwest Indian postmortem sample: a pilot study

Nonmetric traits are quasi-continuous skeletal traits that cannot be measured, but are observed as ranks or scores. In the present study, 8 nonmetric traits of sternum were examined from 343 sternums collected from the autopsy cases. More males, particularly older subjects, had a mesosternal foramen. The frequency of mesosternal foramen, arch-shaped prominence on the manubrium and radial strips on mesosternum significantly increased but that of lateral projection of manubrium decreased in the 30+ year age-group (older individuals). The denticulate costal incisures were found mostly in females and younger subjects; however, the crescent incisures and arch shaped prominence of manubrium were noticed mainly in males and older subjects. Majority of subjects had 'deep and narrow' jugular notch and xiphi-sternum was 'bifid' or 'oblong' in males and 'small sized' in females and younger subjects. Xiphi-sternum was generally found absent in females and younger subjects. The different shapes of costal incisures, jugular notch and xiphoid process were found to have significant sex and age differences. The number of cases with fused elements significantly increased with advancing age in both sexes. The sternal elements' fusion showed a variable pattern and hence was not found to be a reliable criterion. Chi-square analysis revealed significant differences between two age-groups of individual sex in the distribution of 3 of the 8 nonmetric traits. Significant sex and age differences were noticed in the frequency of occurrence of mesosternal foramina between the younger and older age groups in both the sexes. The logistic regression analysis of the scores classified 73.8% sternums to their sex category and 70.0% sternums to their age-group. Though present findings may not be enough for absolute personal identification, these traits can still serve as important identification tools if antemortem radiographs/CT or MRI scans are available for comparisons, or help classify an unknown sternum to its sex or age category based on the morphological features discussed in present study.