Date of Award




Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Biological Sciences

Content Description

1 electronic text (x, 322 pages) : PDF file, illustrations (some color)

Dissertation/Thesis Chair

Caro-Beth Stewart

Committee Members

Richard Zitomer, Min-ho Lee, Christine Wagner


Chimpanzees, Evolutionary genetics, HIV (Viruses), Human genetics, Sexual behavior in animals

Subject Categories

Bioinformatics | Evolution | Molecular Biology


Chimpanzees (Pan troglodytes) and bonobos (P. paniscus) are often used as models to study the genetic and morphological changes on the lineage leading to the modern humans (Homo sapiens). Results of this dissertation suggest that, in comparison to other hominoids, chimpanzees and bonobos are more derived in their relative testes sizes and promiscuous mating systems. Phylogenetic analysis of genes that might underlie increased testes size revealed that, in addition to being a sex-determining gene, SRY displays Pan-specific amino acid replacements that make it a compelling candidate as a testes-size determining gene. Strikingly, SRY and another candidate gene, DMRT3, display patterns of evolution similar to that of relative testes size in the hominoids. Interestingly, DMRT3 displays a very high GC-biased substitution rate on the Pan lineages.