The primary objective of this research is to test the hypothesis that reduction in size of the olfactory system of the brain in higher primates has been accompanied by a significant reorganization at the cellular level. Such reorganization could have allowed some animals previously considered to be microsmatic (having a poor sense of smell)--including humans--to have highly discriminative olfactory systems despite their small size. The Principal Investigators will conduct a quantitative analysis of neurons of the olfactory system, their arrangement, and their interconnections in the brains of several primates and other mammals. The animals to be used in this research are to be received from other investigators and this therefore represents a judicious use of a valuable resource. This research addresses a fundamental question of interest to those involved with either olfactory behavior or anatomy; namely, why do some animals, sensitive to olfactory cues and with seemingly complex social behavioral patterns, have what appear to be diminutive olfactory structures? Anthropologists have traditionally believed that the olfactory system in primates has been reduced at the expense of development of the visual system. This research could demonstrate that long-held tenet of anthropology to be misleading if reorganization of the olfactory system has allowed a small "smell-brain" to be just as efficient in some respects as a large one.
