Cat Behavior - Why Your Cat Hisses

This question actually did not come from my husband this time.
I just had both of my cats hiss today and while I thought that I knew why cats hiss, I decided to satisfy my own curiosity.
The first thing that I discovered is that the hissing sound itself is a form of animal mimicry.
It turns out that the hiss evolved from cats imitating snakes.
When I first read this information, I was skeptical.
However, the more I researched, the more it made sense.
I looked at pictures and videos of snakes hissing and realized that my cats made similar facial expressions and sounds when they hissed.
So I guess this theory is not only possible, but it is plausible.
Usually cats hiss in their own defense or in defense of their territory.
When your cat feels threatened by a person or even another cat, it will bare its fangs and let out a hiss.
This puts the other animal or person on notice that they are unwelcome and better not get too close.
Unusually the cat also spits and its fur is fluffed up and its tail beats back and forth.
Some suggest that this whole body language is reminiscent of a snake when it's about to attack.
Just the way you would back down if you saw a snake behaving like this, I would suggest that you back down if you see a cat doing this.
Whatever you do, please do not try to touch a cat when it exhibiting this behavior.
The next reason that a cat may hiss is because it is annoyed.
For similar reasons that a cat may bite while you pet it, a cat may hiss when you are petting it.
Sometimes your cat has simply had enough and she is just making it clear that you need to stop.
If a cat should hiss when you are petting it, please just stop petting.
The cat will usually move away from you, begin licking itself and forget about the whole episode.
However, if your cat hisses when nothing and no one is provoking her, something else may be going on.
If you notice your cat hissing when there is no reason for her to be defensive or annoyed, she may be sick, in pain or suffering a mental defect.
If this should happen, please take your cat to the vet to have her checked out.
In the end, no matter why your cat hisses, we as humans need to respect the hiss.
Just be the bigger person (literally) and back off.
Ultimately, you and your cat will be better for it.