Why Is the Catarrhine VNO Pheromone Transduction Pathway Dispensible?
Earlier anatomical and physiological studies showed that adults of hominoids and OW monkeys do not have VNOs or functional VNOs, whereas NW monkeys and prosimians clearly have them (1–3, 32, 33). Observations of presumably pheromone-based reproductive or social behaviors are largely consistent with this dichotomy (1, 2, 34), although notable exceptions do exist (35, 36). For example, menstrual cycles tend to synchronize among female humans living in close proximity (37, 38). The molecular basis of the synchronization, however, is unclear, and it may not be mediated by VNO. In fact, certain non-VNO-mediated behavioral responses to putative pheromones have been reported in pigs and rabbits (39, 40). Our evolutionary genetic data from two components of the vomeronasal pheromone transduction pathway are consistent with each other and are in general congruent with the aforementioned anatomical, physiological, and behavioral data. It may be concluded that the VNO-mediated pheromone sensitivi
