Ellen, Oklahoma City asked:
I want to know if humans have a functioning Jacobsonís Organ? As Iíve heard several different opinions on this matter.
This week's Question was answered by Peter Burnham, department of physiology and pharmacology, University of Bristol.
The Jacobsonís organ is part of the vomeronasal system. It senses chemical stimuli such as marks, which tell animals about the sex and individual identity of other members of their species, often called pheromones. The Jacobsonís organ is found in many species but by no means, all species. The question is, whether or not thereís a Jacobsonís organ in humans. People have found a small infolding in the nose of humans and claimed that to be a Jacobsonís organ. The question is, whether or not it is functional. The overwhelming weight of evidence is against this function. For instance, it has a very different appearance from the Jacobsonís organ that you find in other species. There are no nerves that can be found that connect it to the brain and therefore it is unlikely that it can send a signal to the brain. Moreover, there are genes that are vital for the function of the vomeronasal organ/Jacobsonís organ in other species but they donít work anymore in humans. They become redundant during human evolution. That happened at about the time when the new and old world monkeys split off from a common ancestor in Africa many millions of years ago. So it seems very unlikely that the Jacobsonís organ can have any function at all in humans.
Diana: So there is some evidence for its existence in humans, but it seems unlikely that our brains are actually receiving any information from it. It may be that our ancestor hominids had one to detect sex pheromones. Itís more likely now though that you can only tell a man from a woman from their scent, because there are a lot of boys out there who smell pretty awful anyway. Otherwise it may be worth memorising a pour homme or pour femme perfume counter.