Why do we have two nostrils?
• Most animals, and many plants, are bilaterally symmetrical. The evolutionary origin of this trait can be traced back hundreds of millions of years. Our two nostrils are a consequence of this process.
What is much more interesting, though, is that there is little symmetry between the two nostrils, either in shape or function. For example, many people can smell different odours in each nostril, and you can test this yourself.
I have also noticed that when I have a virus, it usually only causes a blockage in one nostril at a time, which I…
