DDIG: Was There a Sensory Trade-off in Primate Evolution? A method of tracing vomerolfaction in the fossil record

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There is a long-standing hypothesis in physical anthropology that a sensory trade-off has occurred between smell and vision in primate evolution. This trade-off is suggested to have taken place during the time that anthropoid primates adapted to a diurnal rather than nocturnal activity pattern. Thus, these primates began using visual stimuli more prominently than smell or chemosensation in communication. While this trade-off hypothesis seems supported by reduction in the anatomical structures related to pheromone detection and enhancement of the visual system in some living primates, it has not been tested using the fossil record. Fossils have largely been excluded from answering this question because features related to chemosensation, particularly the vomeronasal organs, which are important in pheromone detection, do not fossilize. This study identifies bony anatomical features related to chemosensation in primates to understand variation in the expression of these features in living primates and compare the resultant information to fossil primates. We have identified a hard-tissue correlate of primate chemosensation in the form of bilateral bony grooves on the nasal floor, formed by articulation with the cartilage surrounding the vomeronasal organs. The palatal grooves and their relationship to the vomeronasal organs (occurrence, relative size) are analyzed statistically in a range of living primates using histological and CT methods. Skulls of fossil primates that preserve the nasal floor will are also examined using CT to identify the presence, size and morphology of the palatal grooves to understand the timing and context of the reduction of chemosensation in anthropoid primates and test whether this corroborates the sensory trade-off hypothesis.This research promotes graduate education and will result in a Ph.D. for a female graduate student. The data recovered from this project will increase knowledge on the interface of ecology and adaptation in early primates as well as contributing information to understanding reduction of human chemosensation. This research will be made available to the scientific community and the interested public through journals and scientific magazines.