Document Type


Date of Degree Completion

Spring 2022

Degree Name

Master of Science (MS)


Primate Behavior

Committee Chair

Lori Sheeran

Second Committee Member

Nicole Jastremski

Third Committee Member

Joseph Hefner


Macromorphoscopic analysis (MMA) was used to assess variation of ten skull features in 20 western lowland gorilla (Gorilla gorilla gorilla) specimens. Non-metric analysis has been used to document human variation in skulls to track ancestry. MMA has yet to be used in the study of population variation among non-human primates; rather, most studies have been focused on metric variation of dentition and limb bones. Here, western lowland gorilla specimens were chosen based on the availability of digitized skulls, the number of complete skulls of adult individuals, and documented geographical origin of specimens. Twenty adult individuals (14 males and six females) were online collected from the Smithsonian 3D digitalization catalog. The sample was collected from a private online drive, where access was granted by Dr. Matt Tocheri from the Smithsonian and stored on an exterior hard drive for review. After specimens were selected for analysis, a methodology was developed based on previous MMA studies conducted with human specimens (Hefner, 2018). Eight traits common to hominoids were analyzed, as well as two non-human primate traits included to link macromorphoscopic analysis to heritability in non-human traits. Ten traits were scored on each of the 20 individuals using MMA (Hefner, 2018). The data was then analyzed using correspondence analysis in RStudio (RStudio Team, 2022) using several packages: FactoMineR, ggplot2, factoextra, Hmisc, corrplot, MASS, tidyverse, plotly, and wesanderson. These analytical packages interpret and plot data for correspondence analysis. Results were interpreted based on male versus female expression of traits, geographical expression of traits and the expression of traits on each specimen. The results showed that while there were no significant differences among males and females, nor differences in geographical location, there were four traits that showed significant differences in the expression of traits in the overall sample.

Available for download on Wednesday, June 09, 2027