Date of Award
5-2014
Degree Type
Thesis
Degree Name
Master of Science in Integrative Biology (MSIB)
Department
Biology
Committee Chair/First Advisor
Dr. Marcus Davis
Major Professor
Dr. Jared Taglialatela
Second Committee Member
Dr. Antonio Golubski
Abstract
Chimpanzees and bonobos have distinctly different vocalizations, but it is unclear why these differences have evolved. We hypothesized that differences in habitat and feeding ecology have selected for bonobos to have an increased reliance on vocal communication compared to chimpanzees. To evaluate this hypothesis 1571 chimpanzee vocal events and 612 bonobo vocal events were analyzed. After analyzing and coding video of communicative interactions it was determined that chimpanzees are more likely than bonobos to utilize multimodal communication and to direct vocalizations to an individual conspecific. Bonobos were more likely than chimpanzees to produce a vocalization that was not bound to a specific social context. We further hypothesized that these behavioral differences should be reflected in neuroanatomical differences between bonobos and chimpanzees. In humans, there is a left neuroanatomical asymmetry in Broca’s area – an inferior frontal region of the brain known to be involved in language production and processing. Therefore, we hypothesized that this would also be seen in bonobos as they putatively rely on vocal communication more than chimpanzees. However, quantification of the inferior frontal gyrus (IFG) on magnetic resonance images showed that bonobos had a larger right than left IFG, while chimpanzees had a larger left than right IFG. There was also no difference in lateralization of neuropil fraction (a measure of the space between neurons and glial cells in the gray matter) of Brodmann’s areas 44 or 45. These data are discussed in relation to the hypothesis that observed differences in the communicative strategies and neuroanatomy of the two Pan species were driven by differences in foraging strategies since they diverged from a common ancestor approximately one million years ago.