Males use the hormones present in a female's urine to test her reproductive status. Many animals can be seen drawing their lips back and exposing their teeth after smelling in an expression known as a Flehman Grimace. An organ called the Organ of Jacobson is situated in the roof of the mouth and the grimace opens the pathway to the organ, allowing the smell particles to enter. From here, specialized receptors in the brain decode the hormones and provide the male with all the information pertaining to the urine's owner. This may include age, hierarchical status and even mood, as well as her reproductive condition. It is worth noting that an animal can only decode the hormones of its own species (species specific). If this giraffe analyzed the urine from a wildebeest for example, it would not be able to interpret the information.
There is plenty of evidence to support the fact that humans used to possess this ability, and still do to some extent. Modern technology has enabled us to see a similar organ developing in fetuses in the womb but then regressing before birth. Our sense of smell is potentially the most powerful that we have and a mere whiff can instantly transport us back to a very specific time and place.
Thankfully, humans have developed a hugely sophisticated, and diverse, vocal and visual communication repertoire that has negated the need for us to smell each other in such an obvious fashion! Can you imagine the perils of the dating game without our ability to read, write and talk!?
Fact and photos by Ben Coley