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  #1  
Old 02-24-2012, 10:30 PM
Speaker for the Dead Speaker for the Dead is offline
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Did noses evolve for smelling or for breathing?

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?
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  #2  
Old 02-24-2012, 10:51 PM
Colibri Colibri is offline
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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 appears to confirm an intermediate stage in this migration.

Last edited by Colibri; 02-24-2012 at 10:52 PM..
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  #3  
Old 02-25-2012, 02:17 AM
Leo Bloom Leo Bloom is offline
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Colibri, who knew you knew so much about nostrils?
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Old 02-25-2012, 03:24 AM
Blake Blake is offline
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Colibri, who knew you knew so much about nostrils?
He nose his stuff.
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Old 02-25-2012, 03:52 AM
panache45 panache45 is offline
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That's nothing to sneeze at.
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  #6  
Old 02-25-2012, 04:01 AM
Peter Morris Peter Morris is offline
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He makes a lot of scents.
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  #7  
Old 02-25-2012, 05:38 AM
Sunspace Sunspace is offline
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These puns stink.
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  #8  
Old 02-25-2012, 07:19 AM
Peter Morris Peter Morris is offline
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Okay, from now on, puns are strictly No-Nos.
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Old 02-25-2012, 09:35 AM
Polycarp Polycarp is offline
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If you ever figure out how to avoid 'em, sinus up!
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  #10  
Old 02-25-2012, 10:34 AM
Colibri Colibri is offline
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Colibri, who knew you knew so much about nostrils?
C'mon, I've always been a nose-it-all.
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  #11  
Old 02-25-2012, 10:35 AM
Gary T Gary T is offline
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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
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  #12  
Old 02-25-2012, 11:00 AM
Toucanna Toucanna is offline
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Great question and love the puns, just one clarification: not all species of mammals can breathe through their mouths. Horses are one example.
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Old 02-25-2012, 11:11 AM
WhyNot WhyNot is online now
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Quote:
Originally Posted by Toucanna View Post
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.)
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  #14  
Old 02-25-2012, 12:52 PM
psychonaut psychonaut is offline
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Originally Posted by Toucanna View Post
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?
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  #15  
Old 02-25-2012, 12:59 PM
WhyNot WhyNot is online now
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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.
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  #16  
Old 02-25-2012, 01:06 PM
Gorsnak Gorsnak is online now
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Noses evolved for making more babies, same as everything else.
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  #17  
Old 02-25-2012, 01:14 PM
enalzi enalzi is online now
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Quote:
Originally Posted by Colibri View Post
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 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!
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  #18  
Old 02-25-2012, 01:23 PM
Colibri Colibri is offline
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Quote:
Originally Posted by WhyNot View Post
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. 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.
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Old 02-25-2012, 05:22 PM
GiantRat GiantRat is offline
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Y'all may think your pun is funny, but it's not.
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  #20  
Old 02-25-2012, 09:18 PM
Siam Sam Siam Sam is offline
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So what's up with those two lines that come down from the nose?
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  #21  
Old 02-25-2012, 09:38 PM
don't ask don't ask is offline
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And here I was thinking that the nose evolved to facilitate modern office politics.
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  #22  
Old 02-25-2012, 10:00 PM
JKellyMap JKellyMap is online now
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Originally Posted by Siam Sam View Post
So what's up with those two lines that come down from the nose?
Ask Phil somebody. He nose.

Last edited by JKellyMap; 02-25-2012 at 10:02 PM.. Reason: hot chick link, but safe for work
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  #23  
Old 02-27-2012, 01:53 PM
phreesh phreesh is offline
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Somewhat related, but why are the nostrils downward pointing? In the great apes, the nostrils are forward facing, which seems like the more 'natural' way for them to be utilized for the intake of oxygen and odors.

I've read that it's to facilitate swimming, so water doesn't [easily] get into your nose, but that seems pretty far-fetched. Is there a factual answer to this?
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  #24  
Old 03-01-2012, 06:57 PM
Speaker for the Dead Speaker for the Dead is offline
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Guys, wow. I haven't been on the SDMB for months and months, and my first thread nets me BOTH the answer I want and an amazing series of puns. I'm sad I ever left!
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  #25  
Old 03-07-2012, 10:17 PM
Zebra Zebra is offline
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Moses supposes horse noses are hoses, but Moses supposes erroneously.
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  #26  
Old 03-07-2012, 11:29 PM
Autolycus Autolycus is offline
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Quote:
Originally Posted by WhyNot View Post
What selective pressure caused it to be lost in horses, do we know?
Sinus pressure?

Or what Colibri said. One of the two!
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  #27  
Old 03-08-2012, 02:30 PM
Elendil's Heir Elendil's Heir is offline
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Originally Posted by Sunspace View Post
These puns stink.
Then why'd you come sniffing around here?
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  #28  
Old 03-08-2012, 09:43 PM
Chefguy Chefguy is online now
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Then why'd you come sniffing around here?
He's nose it adenoids us.
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  #29  
Old 03-09-2012, 09:49 AM
Tom Tildrum Tom Tildrum is offline
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Quote:
Originally Posted by Colibri View Post
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.
And yet they never discovered oral sex....
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  #30  
Old 03-09-2012, 10:18 AM
psychonaut psychonaut is offline
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Originally Posted by Tom Tildrum View Post
And yet they never discovered oral sex....
On the contrary…
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