Why do mouths dry up when nervous?

[marmaduke]

What's the point of our mouths drying up when we're scared or nervous? I can understand other things like hairs standing on end when cold as a relic of our early-human past, but what's the reason for this?

[MORELLO]

I'm not sure why your mouth dries up, but hairs standing on end when cold isn't some relic from the past. Hairs stand on end to trap a layer of air close to the skin, which will be heated by body temp and act as an insulator. Examples of relics from your past are your sacrum, and third bone (phalange) in your little toe (if you have one - some people have evolved to have only two)

[portocat]

it is an autonomic nervous response.  in times of stress (ie when nervous) your body puts energy into other things, such as increasing heart rate etc, and less effort into making saliva

[marmaduke]

Yes I know it's the insulating layer, but it would have meant a lot more in our savagely hirsute days.

[MORELLO]

How would it mean a lot more? It would serve the same purpose. If you're talking of the meanings of things, you need to word your posts more carefully. If hairs standing on end were a 'relic of our early human past', so would having two legs be.

[marmaduke]

Hairs standing up on end when it's cold would have meant more, I believe, because humans were hairier millennia ago, and so the response would have done more to insulate a person.