Date Approved


Graduate Degree Type


Degree Name

Biomedical Sciences (M.H.S.)

Degree Program

Biomedical Sciences

First Advisor

Dr. Melisa Tallman

Second Advisor

Dr. Dawn Richiert

Third Advisor

Dr. John Capodilupo

Academic Year



Old world monkeys, new world monkeys, and humans all originate from a common ancestor. Although humans and old world monkeys are phylogenetically more closely related, old world monkeys and new world monkeys have similar locomotion. A difference in muscle patterns exists between old world monkeys, new world monkeys, and humans. Different musculature may be due to differences in locomotive patterns and species-specific use of their forearms. Muscles in the forelimbs are innervated by the nerves of the brachial plexus. There are differences among the brachial plexuses of human and non-human primates as well as variability within the species.

In this study, we compared the level of variability of the branching patterns of the brachial plexus between primate species as well as within each primate species. Research has been published on the comparative anatomy of primates of bones and skeletal muscles; but little research has been reported on the neural pathway supplying these muscles. Muscular patterns changed with the evolution of locomotive pattern from quadrapedalism to bipedalism. The rates of evolution have been found to be higher in species that locomotive patterns diverged from sister taxon. Understanding the brachial plexus and its level of variability will help better understand the evolution of primate locomotion. Differing levels of variability have been attributed to the evolution of locomotive patterns.

This study analyzed 51 individual specimens and 81 individual brachial plexuses of old world monkeys, new world monkeys, and Homo sapiens. Each of the specimens were photographed and a written description given. The results showed that old world monkeys and new world monkeys exhibited similar levels of variability which were collectively higher than that of Homo sapiens. Discussions of these variant branching patterns and levels of variability help build an understanding of the results discovered in this study.

Available for download on Sunday, August 20, 2023