Jacobsons organ in Humans?

07 October 2007

Question

I want to know if humans have a functioning Jacobson’s Organ? As I’ve heard several different opinions on this matter.

Answer

This week's Question was answered by Peter Brennan, Department of Physiology and Pharmacology, University of Bristol.

The Jacobson's 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 Jacobson's organ is found in many species but by no means, all species. The question is, whether or not there's a Jacobson's organ in humans.

People have found a small in-folding in the nose of humans and claimed that to be a Jacobson's 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 Jacobson's 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/Jacobson's organ in other species but they don't 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 Jacobson's 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. It's 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.

Comments

I have been researching this topic for some time now, and the science is very limited compared to a large amount of anecdotal studies on the topic. For example, there are studies that suggest a pheromone called androstadienone has an effect on cortisol levels in women, can reduce pain, and can be comforting to women during ovulation. Several social tests have also proven that women rate men higher than average, than those who aren't exposed to the pheromone. [SPAMMY LINK REMOVED]

While doing nasal endoscopies on each other I was found to have this organ. I have been told that senses can be elevated and beyond smelling a woman from a man I did notice a good sense of reading fear and other emotions from people. It could be possible. And I now know that my relatives are Neanderthals!

Paul, you said "by doing endoscopies" - but what Peter Brennan points out above is that although there is an in-folding that might resemble the VMO (vomeronasal organ) in the human nose, it's not clear that it actually funcations as such. So how do you know, from your endoscopy, that this is the case?

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