My current research centers on the evolution of the primate hearing sense using a multifaceted and interdisciplinary approach.
The ecology and evolution of primate hearing
The reception of acoustic signals and cues is vital to the survival and reproductive success of primates, and thus has likely played a significant role in the evolution of human and nonhuman primates. Yet for decades our understanding of how and why auditory sensitivity varies among primates has been little understood, in part due to the logistical challenges of testing primate hearing via traditional methods. The lack of a data set sufficient to allow full exploration of auditory-ecology relationships has resulted in a long-held dogma that primate hearing is unspecialized and solely a consequence of size. This is surprising considering the strong interest in vocal communication and language evolution throughout anthropology.
I addressed the void in comparative data with my Ph.D. research at the University of California, Santa Cruz (Nathaniel Dominy’s lab). Working with Jim Finneran at the U.S. Navy Marine Mammal Program, we developed a portable evoked potential system for testing primate auditory sensitivity in the lab and in the field, using a safe, efficient, and minimally invasive auditory brainstem response (ABR) method originally developed for human infants. The ABR method enables the measurement of auditory sensitivity in virtually any animal species in approximately 30-60 minutes. Using the ABR method, my colleagues and I have tested the auditory sensitivity of howling monkeys in Costa Rica, tarsiers in the Philippines, eleven strepsirrhine taxa at the Duke Lemur Center, and platyrrhine monkeys at the California National Primate Research Center and various collaborating laboratories.
I also collect data on habitat acoustics (e.g. forest structure) and the properties of acoustic signals and cues present within the natural habitats of the species that I study. Such data allows variations in auditory sensitivity to be understood in an ecological and evolutionary context.
The comparative and functional morphology of the bony labyrinth
The bony labyrinth is a region of the cranium (temporal bone) that houses the organs of hearing (within the cochlea) and balance (within the vestibule and semicircular canals). At MPI-EVA, I am working with Fred Spoor to explore the primate bony labyrinth using CT scanning and 3D geometric morphometrics. This work is an expansion of Spoor’s previous work on the morphology of the semicircular canals to include a 3D approach, additional species and age classes, and a more detailed consideration of the cochlea. For additional information please see Fred Spoor’s research page.