Evolutionary purpose of the nasal septum?

[CurvKyle]

Does anyone have any ideas on why we have a nasal septum and what purpose it might have served in the Evolutionary process?

[ecoli]

so it can be pierced?

[bascule]

I'd imagine if it were removed your nose would lose a lot of structural integrity

[ecoli]

the septum is just the part in the middle, separating the two nostrals. Is there an advantage of having two nostrals as opposed to one? Maybe it's a matter of symmetry?

[Mokele]

It's a leftover, a developmental relic. Originally the "nose" was simply a pair of pits on each side of the snout, containing chemoreceptors. In early lungfish, the pits became tubes connecting to the inside of the mouth. In synapsid reptiles, the pits moved to the back of the mouth and, eventually past the pallate, resulting in the mammalian condition.

 

IIRC, several defects of bilateral development result in (non-viable) fetuses with only a single nostril.

 

So basically, it's not there because it's an adaptation, it's there because it's a developmental consequence of our evolutionary history.

 

Mokele

[gcol]

double post, sorry.

[gcol]

I reckon it is much simpler than all the above:

 

Without the septum, when you inhaled, your nose would close, like a flap-valve: when you breathed out, it would make a noise like a whoopy cushion.

 

Why two nasal orifices? Olefactory focussing and backup facility of course, so you can tell who has farted, and when I am digitally unclogging one nostril, I can still breathe through the other.

 

Are there not some animals, seals and camels for example, that can open and close their nasal flaps at will?

[Mokele]

Without the septum, when you inhaled, your nose would close, like a flap-valve: when you breathed out, it would make a noise like a whoopy cushion.

 

Not actually, the nose is full of elastic cartilage that provides more than ample support to prevent this.

 

Why two nasal orifices? Olefactory focussing and backup facility of course, so you can tell who has farted, and when I am digitally unclogging one nostril, I can still breathe through the other.

 

Actually, mammals are incapable of directional smell. Although there are two nostrils, the airstreams fuse and intermix in the nasal cavity.

 

Are there not some animals, seals and camels for example, that can open and close their nasal flaps at will?

 

Yes, though that's not really relevant.

 

Mokele

[JHAQ]

A consequence of bilateral symmetry ?

[gcol]

But then why have I got only one mouth, one anus and one ...errr.. you know what. One is symmetrical too, you know, as long as it is in the middle. Might be fun with two of the other things