Ch.8: Sex Estimation

Sexual Dimorphism

• The “expression of phenotypic differences between males and females of the same species” (p. 203)

• Not as extreme in humans as in some other species

Sex Estimation

• Sexual Dimorphism

• Utilizes changes in shape and size of the skeleton related to secondary sex characteristics

• Biological males are about 15% more robust than biological females

• Various methods for estimation

Various methods for estimation

• Metric and morphological (nonmetric)

• Pelvis is the best indicator

Sex

• “Refers to an individual’s genetics and biology” (p. 204)

• Estimable from skeletal remains

Gender

• A “cultural expression” of identity (p. 204)

• Not estimable from skeletal remains

Indicators of non-conformity to biological sex

• Evidence of surgical gender-affirming medical procedures (i.e., facial feminization surgery, etc.)

• Contextual information (clothing, personal effects, etc.)

Morphoscopic Sex Estimation Methods

• Visual assessment of features which vary between biological males and females

• Methods involving the pelvis are most accurate

  • Childbirth

• Methods involving the skull are second-most accurate

• Must use multiple methods for a thorough estimation

  • Do not use one method in isolation

Morphoscopic Sex Estimation Methods (Scoring of Pelvis)

• Character state scores for the varying degrees of expression of the three pubic traits for sex estimation

  • Phenice (1969) pelvic sex estimation traits

• Scores of 1-2 represent more female expressions of the traits whereas scores of 4-5 represent more male expressions of the trait (From Klales et al., 2012)

• Females usually have a pronounced subpubic concavity (subpubic contour) and have a ventral arc, whereas males lack these features; females have a sharp ischiopubic ramus ridge while males have a blunt ridge

Phenice (1969) pelvic sex estimation traits

• Subpubic countour

• Medial aspect of the ischiopubic ramus

• Ventral arc

Morphoscopic Sex Estimation Methods (Scoring of Skull)

• Cranial trait scoring for sex estimation; Scores 1-2 represent a more female expression while scores 4-5 represent a more male expression for each trait

Other Morphoscopic Sex Estimation Methods

• Sex-related susceptibilities to certain diseases and skeletal conditions

  • Ex., hyperostosis frontalis interna is more common in biological females

• Gracility or robustness of muscle attachments

Metric Sex Estimation Methods

• Sex estimation based upon sectioning points

• Single measurements

• Index of two measurements

• Multivariate analyses

• Those based on long bone measurements are often the most accurate

• Population-specific

• Males are typically larger than females

Sex estimation based upon sectioning points

• Measurements of “maximum or minimum dimenstions or… [those] based on osteological landmarks” (p.212)

Multivariate analyses

• Discriminant function

• Random forest modeling

Metric Sex Estimation Methods

• Maximum femoral head diameter

• Postcranial element measurements

• (hu)MANid

• Fordisc

Subadult Sex Estimation

• Very low accuracy and high inter-observer error

  • Secondary sex characteristics do not develop until 14 years of age

    • Most methods (metric and non-metric) are dependent upon these characteristics

• Some methods have been developed

  • Morphoscopic

    • Features of the fetal pelvis, etc.

  • Metric

    • Measurements of the humerus and femur (up to 1 year old)

      • Measured from radiographs

    • Diaphyseal dimensions

Other Considerations

• Parturition

  • Childbirth may leave “various lesions on the pelvic bones” (p. 215)

• Geometric morphometrics (below)

  • Robust analytical method which uses shape and size

• Molecular methods (i.e., DNA)

• Proteomic analyses of tooth enamel