I can understand why we have two eyes (judge distance) and two ears (locate sound), but why two nostrils?
-- J.R., Cardiff
Stereolfaction doesn't make much sense, unless it has something to do with locating dinner. So let's look elsewhere. Your nose's most important job is to protect your lungs by warming, cleaning, and moistening inhaled air. For this, the air has to come in contact with the mucus lining and the millions of tiny hairs in our nostrils. The central membrane dividing what would otherwise by one big nose hole adds extra surface to condition our breath, not to mention keeping us from inhaling large bugs and small birds.