Only the nose knows

The researchers identified a transient receptor potential ion channel (TRP) in rats that is likely to participate in VNO sensory transduction, which is involved in the detection of pheromones. But they noted that the human ortholog of TRP2 is likely to be a non-functional pseudogene and that the human VNO may be a non-functional remnant of a time when human breeding depended on pheromone detection.

The Harvard researchers suggested that because breeding no longer depends on pheromones, receptors involved in VNO signaling have accumulated detrimental mutations and have become non-functional. In fact, they suggested that the VNO and the portion of the brain to which the VNO sends its signals in rats may be altogether useless in humans...