Abstract of Daria Vojcic’s 2008 undergraduate honors thesis
In the study of primate evolution, the importance of visual specialization has often been emphasized
over other sensory systems. In order to evaluate the relationship between visual and olfactory function
in diurnal haplorhines, measurements of optic foramen index (OFI) as an indicator of visual acuity and
cribriform plate area as an estimate of olfactory bulb size were obtained from skulls of 12 species of
New World monkeys (including three species of Alouatta), five species of Old World monkeys, and
four species of nonhuman apes. Results showed no evident trend for an increase in visual acuity at
the expense of olfaction in diurnal haplorhines. As noted by many authors, there was no significant
difference in relative cribriform plate area, i.e. olfactory bulb volume, between platyrrhines and
catarrhines. In addition, there were no significant differences in size-adjusted OFI values between
platyrrhines and catarrhines. This counters the idea that catarrhines reduced their olfactory function in
favor of visual processing. However, diurnal haplorhine folivores had significantly smaller relative OFI
values than frugivore-omnivores. There was no significant relationship between cribriform plate size
and diet. These results indicate that among diurnal haplorhines diet is a selective pressure governing
the size of sensory structures and that the trend is independent of phylogeny.