SELECTIVE REDUCTION. “While anthropoids may have olfactory deficits, the reduction is probably selective. One chemosensory system is fundamentally altered in anthropoids. A functional vomeronasal system is clearly lacking in catarrhines, and there is anatomical and genetic evidence for a reduction in some NW anthropoids.”
http://onlinelibrary.wiley.com/doi/10.1002/ar.23035/full