Kid Questions: Why do we have noses?

by Deb on November 17, 2009

This is such a great question!  Partly because I’m a human biologist at heart so I like talking about things like this, partly because at one level the answer is “We don’t know.”

Firstly, noses are for smelling.  We don’t think about it much, but smelling is the oldest sense and is very important.  All the other senses tell you about things that are happening right now, close to you.  Smell can tell you about something that happened before you got here, or something that happened far away.  It can warn you that something dangerous is coming like when you smell fire, or warn you not to eat that meat.  Smell is a part of taste, which is why food tastes funny when you have a cold and your nose is blocked.  And smell is a big part of emotion and memory – when I smell roses it always makes me think of my mother.

Horse's nose

Next, noses are for breathing, and apart from when they’re blocked they’re better at it than your mouth.  Your nose has lots of blood and snot inside it for a reason.  The blood helps warm up the air, so the cold it isn’t a shock to your lungs.  Try taking a deep breath through your mouth when it’s really cold and it will make you cough.  The snot is to catch things you wouldn’t want going into your lungs, like dust or pollen or flies if you’re really unlucky 😀  Breathing through your nose lets you eat at the same time, which is important for babies.  It would be hard for them if they had to let go and breathe while drinking their milk, and it’s one reason they are very unhappy when they have a cold.

nasal cavity

In this picture you can see where the air goes when you breathe through your nose, the big flaps have extra blood in them and help make the snot.  The big pink thing at the bottom is your tongue.

So why do humans have a nose that sticks out?

Nose

For most animals, the whole bottom of their face sticks out and they have a snout with a mouth and nose at the end.  But humans have a flat face and just a nose that sticks out.  We used to have the whole face sticking out, but our jaws got smaller and smaller.  Because our noses still needed space to do their job, they had to stay sticking out.  People who come from very cold areas have bigger noses than people from where it is hot, so they can warm the air up more.

What we don’t know is why our nostrils point down instead of forwards like other animals.  It might be to protect them from dust, it might be so they can help clear in front of our mouth, it might even be so it’s easier to swim without getting water up your nose.  It’s one of the questions scientists are still trying to answer.  Isn’t it fun?

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