Re: Why does warm water cause a gag reflex?

This is an interesting question, but I don't think there is a good answer
for it. Frankly, before I'd believe it is real (the two people I asked
after receiving this question said "I like to drink warm water"), I think
you need to settle your own question of whether it is a cultural issue. 

It is highly likely that you and your friends have many things in common
(age, geography,food preferences in upbringing) which could magnify any
cultural effect. 

Set up a booth on campus and get people to taste water. A university should
have many students from around the world who would give you a more diverse
sample. An easier experiment would be to set up a poll on a social
networking site... try to get more information than just "I like warm
water" or "warm water makes me barf." Ask for age, gender and where people
grew up. 

As for your evolutionary speculation, it is not unreasonable, but I don't
really know any way to test it.