Methods used for biological sex identification

Dental/Odontological Methods: The teeth exhibit sexual dimorphism in characteristics like crown size, root length, and the dimensions of the canine teeth, which are typically larger in males. These methods are particularly useful for young individuals whose skeletal secondary sexual characteristics haven't fully developed.

Molecular (Genetic/Proteomic) Methods: These are highly accurate methods that analyze biological material:

DNA Analysis (Genomic): The preferred technique involves Polymerase Chain Reaction (PCR) to target the amelogenin gene, which has different sizes on the X and Y chromosomes (a 6-base pair deletion is present on the X homolog). The presence of both forms (X and Y) indicates a male, while the presence of only the X form indicates a female.

Protein Analysis (Proteomic): This technique, often applied to tooth enamel due to its preservation quality, tests for the presence of the amelogenin-Y isoform protein, which is only found in males.

Q2. What is photo-superimposition?

Photo-superimposition (specifically Craniofacial Superimposition) is a forensic identification technique used to determine if an unknown skull or set of skeletal remains belongs to a specific missing person.

It involves the following process:

Overlaying Images: An image (or model) of a recovered skull is digitally or physically overlaid and aligned with an ante-mortem photograph (taken before death) of the suspected missing person.

Scaling and Orientation: The two images must be carefully scaled to the same size and oriented to the exact same viewing angle. This often involves aligning anatomical landmarks on the skull with corresponding facial features in the photograph (e.g., eye sockets, nasal spine, jawline).

Comparative Analysis: The forensic expert examines the superimposed image for anatomical consistency. If the key features and bony landmarks of the skull align precisely with the soft tissue outlines of the face in the photograph, it provides evidence that the skull could belong to that individual.

Primary Use and Significance: The technique is generally more effective for exclusion (ruling out a potential match) than for positive identification. A significant mismatch between the skull and the photograph can definitively exclude the individual. While a high degree of concordance is strongly suggestive, a positive identification typically requires supporting evidence from more conclusive methods like DNA analysis.

Sample Answer

Q1. What are the methods used for biological sex identification?

Biological sex identification, particularly in forensic anthropology or bioarchaeology when dealing with skeletal remains, utilizes several key methods, which can be broadly categorized as follows:

Skeletal/Morphological (Macroscopic) Methods: These methods assess sexually dimorphic traits (differences in size and shape between males and females) in the skeleton.

Pelvis: This is the most reliable area for sex estimation in adults, due to differences related to female childbirth capacity. Key traits include the wider sub-pubic angle, the presence of a ventral arc, and a wider/shallower greater sciatic notch in females.

Cranium (Skull): Features on the skull provide a reliable estimate, although less accurate than the pelvis. Traits examined include the overall size and robusticity, the prominence of the supraorbital ridges (brow ridges), the size of the mastoid process, and the shape of the chin (mandible).

Postcranial Bones (Long Bones): Measurements (metric methods) of long bones like the femur and humerus (especially the diameter of the head of the bone) can also be used, though their accuracy is often population-specific.