Two Nostrils enables us to notice things better. Have you at any point seen that, for the duration of the day, one nostril cavity can 'suck' more air in than the other? This isn't a physiological slip-up with respect to mankind, this is in fact something to be thankful for.
Lets have a little life systems lesson first (however I let it be known has been a year since my last life structures and physio class). the structure of the nose is so that 'odors' (read: coasting particles) are recognized by an accumulation of nerves inside the nasal tract. The particles dock inside particular locales of these nerves and the data is in this manner sent to the cerebrum to translated. So what does this hav to do with having two nostril holes? Some 'scents' require time to dock at these locales upon the olfactory nerves, while other 'odors' can rapidly hurdle through those districts. Having one nostril that breaths slower, and another which breaths speedier, enables these olfactory nerves to get a far more extensive scope of scents.