# Did noses evolve for smelling or for breathing? **URL:** \ **Category:** Factual Questions\ **Created:** [February 25, 2012, 4:30am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919 "2012-02-25T04:30:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Speaker\_for\_the\_Dead](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@Speaker\_for\_the\_Dead](https://boards.straightdope.com/u/Speaker_for_the_Dead)\ **Post date:** [February 25, 2012, 4:30am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/1 "2012-02-25T04:30:30Z")
Background: I’ve taken the intro-level university paleontology classes, but they don’t cover the burning questions like “what were noses originally for?” So, currently mammals can breath through their noses or through their mouths, which is a little redundant, and a lot of lower animals get by fine without noses at all. That’s what got me wondering: can we tell from the fossil record/current biology whether noses were initially developed as air passages (e.g. breathing while eating, breathing with most of an animal submerged, making sounds) or as passages to get air flowing by olfactory nerves? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2012, 4:51am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/2 "2012-02-25T04:51:16Z")
Nostrils were originally purely for smelling. Fish have two nostrils on either side of the nose that open into a blind sac, unconnected to the mouth, that contains odor receptors. Water enters through one nostril and then leaves through the other. Apparently at some point one pair of nostrils migrated inside the mouth where they became the internal nostrils (choanae) that permit air to be taken into the lungs. [A recent fossil](http://www.newscientist.com/article/dn6607-fish-fossil-confirms-origin-of-nostrils.html) appears to confirm an intermediate stage in this migration. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [February 25, 2012, 8:17am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/3 "2012-02-25T08:17:13Z")
**Colibri** , who knew you knew so much about nostrils? ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 25, 2012, 9:24am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/4 "2012-02-25T09:24:22Z")
> [@Leo\_Bloom](#): > > **Colibri** , who knew you knew so much about nostrils? He nose his stuff. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [February 25, 2012, 9:52am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/5 "2012-02-25T09:52:08Z")
That’s nothing to sneeze at. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [February 25, 2012, 10:01am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/6 "2012-02-25T10:01:34Z")
He makes a lot of scents. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [February 25, 2012, 11:38am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/7 "2012-02-25T11:38:13Z")
These puns stink. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [February 25, 2012, 1:19pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/8 "2012-02-25T13:19:50Z")
Okay, from now on, puns are strictly No-Nos. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [February 25, 2012, 3:35pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/9 "2012-02-25T15:35:47Z")
If you ever figure out how to avoid 'em, sinus up! ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2012, 4:34pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/10 "2012-02-25T16:34:12Z")
> [@Leo\_Bloom](#): > > **Colibri** , who knew you knew so much about nostrils? C’mon, I’ve always been a nose-it-all.🙂 ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [February 25, 2012, 4:35pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/11 "2012-02-25T16:35:33Z")
> [@Polycarp](#): > > If you ever figure out how to avoid 'em, sinus up! What’s to figure out? It’s as plain as the…oh, never mind ---
**Author:** ![Toucanna](https://avatars.discourse-cdn.com/v4/letter/t/3bc359/32.png) [@Toucanna](https://boards.straightdope.com/u/Toucanna)\ **Post date:** [February 25, 2012, 5:00pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/12 "2012-02-25T17:00:36Z")
Great question and love the puns, just one clarification: not all species of mammals can breathe through their mouths. Horses are one example. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [February 25, 2012, 5:11pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/13 "2012-02-25T17:11:23Z")
> [@Toucanna](#): > > Great question and love the puns, just one clarification: not all species of mammals can breathe through their mouths. Horses are one example. I did know that. So, Mr. Nose-it-all (;)) How does that happen? If there was something after-the-fish split off that developed internal nostrils, how come not all mammals have internal nostrils? Did some proto-horse have them and then lose them, so modern horses don’t have them? It seems like since so many mammals can breathe through their noses, for at least most of their lifespan, that it would have had to be a long time ago that it developed. What selective pressure caused it to be lost in horses, do we know? (I know this is a thoroughly garbled post with flagrant mis-uses of evolutionary terms, but I hope you get the gist of what I’m asking.) ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [February 25, 2012, 6:52pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/14 "2012-02-25T18:52:09Z")
> [@Toucanna](#): > > Great question and love the puns, just one clarification: not all species of mammals can breathe through their mouths. Horses are one example. Breathing, as I understand it, involves moving air into and out of the lungs—i.e., inhaling and exhaling. When it comes to mouth breathing, horses clearly have no trouble with the latter, as anyone who has heard them vocalize can attest. So what’s preventing them from inhaling? ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [February 25, 2012, 6:59pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/15 "2012-02-25T18:59:27Z")
I just realized post 13 is moronic and I’m a drooling idiot. So sorry. Please ignore me today. I’d blame it on the cold medicine, only I’m not taking any. :smack: ---
**Author:** ![Gorsnak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gorsnak/32/7587_2.png) [@Gorsnak](https://boards.straightdope.com/u/Gorsnak)\ **Post date:** [February 25, 2012, 7:06pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/16 "2012-02-25T19:06:13Z")
Noses evolved for making more babies, same as everything else. 😛 ---
**Author:** ![AlsoNamedBort](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alsonamedbort/32/3213_2.png) [@AlsoNamedBort](https://boards.straightdope.com/u/AlsoNamedBort)\ **Post date:** [February 25, 2012, 7:14pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/17 "2012-02-25T19:14:24Z")
> [@Colibri](#): > > Nostrils were originally purely for smelling. Fish have two nostrils on either side of the nose that open into a blind sac, unconnected to the mouth, that contains odor receptors. Water enters through one nostril and then leaves through the other. > > Apparently at some point one pair of nostrils migrated inside the mouth where they became the internal nostrils (choanae) that permit air to be taken into the lungs. [A recent fossil](http://www.newscientist.com/article/dn6607-fish-fossil-confirms-origin-of-nostrils.html) appears to confirm an intermediate stage in this migration. Interesting. When I saw the question, I immediate thought, “it had to be breathing, otherwise why would air be drawn in.” Ignorance fought! ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [February 25, 2012, 7:23pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/18 "2012-02-25T19:23:09Z")
> [@WhyNot](#): > > I did know that. So, Mr. Nose-it-all (;)) How does that happen? If there was something after-the-fish split off that developed internal nostrils, how come not all mammals have internal nostrils? Did some proto-horse have them and then lose them, so modern horses don’t have them? Horses have internal nostrils like other mammals. However, they have an unusually tight seal between the epiglottis and soft palate that blocks off the pharynx (entrance to lungs) when they are not swallowing. Horses, rabbits, and rodents are regarded as [obligate nasal breathers.](http://en.wikipedia.org/wiki/Obligate_nasal_breathing) Whales, for obvious reasons, have developed a separation between the respiratory and digestive systems in order to permit them to breathe and swallow at the same time. ---
**Author:** ![GiantRat](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@GiantRat](https://boards.straightdope.com/u/GiantRat)\ **Post date:** [February 25, 2012, 11:22pm UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/19 "2012-02-25T23:22:43Z")
Y’all may think your pun is funny, but it’s not. ---
**Author:** ![Siam\_Sam](https://avatars.discourse-cdn.com/v4/letter/s/d78d45/32.png) [@Siam\_Sam](https://boards.straightdope.com/u/Siam_Sam)\ **Post date:** [February 26, 2012, 3:18am UTC](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919/20 "2012-02-26T03:18:17Z")
So what’s up with those two lines that come down from the nose? [Next page](https://boards.straightdope.com/t/did-noses-evolve-for-smelling-or-for-breathing/613919.md?page=2)