Cover Letter for American Journal of Physical Anthropology.

Dr. Christopher Ruff
Editor-in-Chief, AJPA
Center for Functional Anatomy and Evolution
Johns Hopkins University School of Medicine
1830 E. Monument Street, Room 302A
Baltimore, MD 21205

Dear Dr. Ruff:

I am writting to present the manuscript that summarize my thesis investigation for the professional degree of Physical Anthropologist of the University of Chile. The manuscript it’s entitled “Predictable value of cranial traits used in the visual assessment of sex: a Geometrics Morphometrics analysis”.

This investigation develops a new aproach to evaluate visual sex assessment methods in cranial traits, and to set a populational validation for this method by geometrics morphometrics (GM).

We select five cranial traits used in visual sex assessment (glabela, mastoid process, zigomatic process of the temporal, zigomatic bone and orbital form) to be measured by 3D coordinates. For these features, the shape variabilty between female and male skulls in a sample with know sex was registered by GM to discriminate wich traits were reliable sex estimators. In contrast to previous publications, our methods rests in the application of GM metrics more than the interobserver error measurement showed by another investigators.

Whit this work publication, we hope to aid in the improvement for the skull visual sex assessment methods to be applied in fields like bioachaeology or forensic anthropology.

Sincerely,


Pablo Díaz Jarufe
Physical Anthropologist
University of Chile.

Predictable value of cranial traits used in the visual assessment of sex: a Geometrics Morphometrics analysis.

Sex assessment it’s one of the cornerstones for any investigation in physical anthropology. It can be realized by means of visual examination of the cranium or the hip bone. Populational validation for these methods it’s perform by experienced observers estimating the sex in osteologycal collections with known sex. A problem with these methods it’s that they are validated minimizing the interobserver error for sex assessment and not by the biological varibility measurement of these traits. Five cranial traits for sex determination (glabella, mastoid process, zygomatic process of the temporal, zigomatic bone and orbital form) were recorded in a set of 3D landmark coordinates and analized by geometrics morphometrics. The aim of this investigation was the metric assessment for the reliability of these traits for sex visual assessment. The coordinates set for each trait were statistically compare between females and males, and by Generalised Procustes analysis (GPA) and thin-plate splines for size and shape variables to carry out a discriminant analysis and to visualize they morphological variation. Significant differences between sex were found for glabella, mastoid process, zygomatic bone and zygomatic process of the temporal. Discriminant analysis for size and shape variables gave significant clasification for sex over 89% of the sample. 3D thin-plate splines visualization of form for these traits described the morphological variation from hyperfeminine to hypermasculine cases. These results may improve visual methods to sexing skulls and demostrate that geometrics morphometrics could be a powerful tool for populational validation of these methods.

Keywords: sex estimation, sexual dimorphism, geometrics morphometrics, populational validation

Predictable value of cranial traits used in the visual assessment of sex in the chilean population: a Geometrics Morphometrics analysis.

The variation of five cranial traits used in the visual assessment of sex were recorded in a set of landmarks coordinates and analized by geometrics morphometrics methods to put into practice a metrical method to evaluate the reliability of this traits for sex determination in chilean population. The cranial traits analized were glabella, mastoid process, zygomatic process of the temporal, zigomatic bone and the orbital form. The 3D coordinates for morphometrical analysis were taken from 120 craniums (60 male, 60 female) with know sex from the Cemeterio General collection of the Anthropology Department of the University of Chile. The coordinates set for each trait were compare between females and males through a permutation test for means difference, and by Generalised Procustes analysis (GPA) and thin-plate splines for size and shape variables to carry out statistical analysis and to visualize the morphological variation for this cranial trais. Significant differences owed to sex were found for glabella, mastoid process, zygomatic bone and zygomatic process of the temporal and the size and shape variables discriminant functions gave significant clasification for sex over the 89% of the sample cases. The 3D thin-plate splines visualization and the size and form varition of this traits allowed us to describe the morphological variation from hyperfeminine to hypermasculine cases of this population, descriptions that could be applyed to methods for cranium visual sex assesment. Finally, we conclude that this cranial traits can be measured to validate this methods in a particular population