Tracking them all: exploring age-related variation in sexual dimorphism of the human pelvis
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Date
2021
Authors
Sanchez, Jose
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Abstract
Determining the biological characteristics of a skeleton, which include age, sex, and
stature, is an integral step in skeletal analysis for bioarchaeologists and forensic
anthropologists. Although sex determination in adult skeletons is highly accurate,
particularly when conducted on the pelvis, this type of analysis continues to elude the
field of juvenile osteology. It has been proposed that sex traits on the pelvis do not
become sufficiently dimorphic until adulthood. This research examined age-related
variation in the expression of sexual dimorphism in the human pelvis from an
ontogenetic perspective. The main objective was to identify the age of appearance and
stabilization of morphological and metric sex differences in the pelvis. This research
also explored the relationship between sexually dimorphic pelvic traits and the
attainment of puberty. Eighteen morphological traits and nine logistic regression
equations were examined on 128 subadults (51 females and 77 males), aged 4 months
to 20 years, from the Hamann-Todd and Terry Skeletal Collections. Pubertal stage
assessment was also conducted based on skeletal indicators. This research showed
that age-related trends exist in the appearance and stabilization of morphological pelvic
traits. Three general patterns emerged from this research: traits either showed a male
“default” expression, a female “default” expression, or concurrent sex expressions by
birth or the time of pelvic fusion. Ten of the 18 morphological traits examined had an
accuracy of 80% or above in individuals 17-20 years of age. Additionally, this research
showed that the post-pubertal period is not required for the full expression of sexual
dimorphism for all morphological traits. Instead, surpassing peak height velocity was
shown to be more important since four traits and overall sex assessments showed
substantial dimorphism occurring in the deceleration pubertal stage. Only one of the
logistic regression equations tested in this research proved to be effective for sex
assessment in subadults. Moreover, metric methods appeared to be best employed with
age estimates as opposed to developmental (pubertal) stages. The novel strategy
employed in this research to address subadult sexual dimorphism proved insightful to
understand the complex nature of sexual dimorphism in the human skeleton.
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Keywords
Sex estimation; Growth and development; Bioarchaeology; Forensic anthropology