Human Sexual Polymorphism and Predicted Ranges of Morphological Variation in Human Skeletal Sex Indicators

Objective

Humans, while most often considered to be sexually dimorphic by biologists, exhibit a greater range of variation in sex traits than is generally acknowledged. Intersex individuals, or those with a combination of traits traditionally considered male, female, and/or atypical for either, represent some of this variation. While much study has been devoted to characterizing sex differences and estimating sex in the human skeleton, skeletal variation in sex traits is unknown for intersex individuals.

Materials and Methods

Informed predictions of the relative level of skeletal sex indicator expression for nine forms of intersex were created using a recent endocrinological text with a section focused on intersex variations. Predictions of skeletal sex indicator expression in standard sex indicators were defined as low, intermediate, or high.

Results

Results predicted that skeletal sex indicator expression is expected to be low for individuals whose form of intersex is complete androgen insensitivity (CAIS), monosomy X, and XY gonadal dysgenesis; intermediate for those whose form of intersex is 5α-reductase (5α-RD), partial androgen insensitivity (PAIS), congenital adrenal hyperplasia (CAH) (21-hydroxylase variations), Müllerian agenesis, and XXY; and high for those whose form of intersex is CAH (11β-hydroxylase variations) and hypospadias.

Conclusions

These predictions may be used for testing hypotheses on intersex skeletal variation when skeletal remains and/or data are accessible with the consent of intersex individuals.