Correction, vampires and werewolves were not imagined, I know a werewolf but I have heard of the reality of vampires.
But if they didn't exist, I'd guess they'd come from random imagination, stories made up - how was Jesus, Buddha, Father Christmas, the Hindu gods and Mohammad, etc made up? Same way I could make up that there was a thirteen eyed massive spider stuck to the ceiling the size of a car! Back to reality...
In mythology they have been acclaimed their fiction from mythic explanations:
Let's start with vampires seen as it was the first one listed:
Modern day vampires (their image) came from an extension of Bram Stoker's book of which he could not think nothing more but the ancient cultures, he invented most of the vampire's characteristics.
But we have no idea of where werewolves came from as there are so many influences of the same image all over the world, even in places they are either extinct or never lived there. So how'd they explained that, but if werewolves did not connect with these countries, nor wolves, then surely wolves or werewolves did exist and/or the myths were imported or their reality was.
When I was at school my English teacher on a few occasions told me to invent stories of which I invented my own creatures or invented new opinions of the already existent background of them. It is easy, trust me.
Someone would of originally invented them.
Understand me, that there is still a possibility these still could of existed and I have evidential information. I have used and edited this to make more sense and I have given four years to the biology of lycanthropy. Please respect my work and copy it for informational purposes only.
Bit of science:
Let's start with vampires - they are driven by a bacteriophage based on blood, it'll eat blood until there is nothing left and that's why they'll need new blood and not too sure on how it works but the vampirism captures four genes, bacteriophage, something that gives them fangs, something that makes them allergic to Vitamin D, usually via sun rays, either instant or over time and something bacterial flushing, re-animating them, giving them a close to immortality age, like 1,000 years at maximum, theoretical the bacteriophage.
I have sourced this from someone else's work but I can't give it a 100% positive.
Yet I do know alot on werewolves, with 100% reality on werewolves.
I think you have coined what a werewolf is from films, not from reality. Yes there are many forms and are actually all of them, it is all to do with the gamma spectrum.
I'll provide some information of the science of werewolves in reality and you will be able to assimilate what they are really, I know they go by things like magic, etc but I have wrote a piece on the chemistry of it and here it is:
The lycanthropy, classed as a virus by metamorphic scientists and biologists is a form of DNA manipulation that will try to target several areas of the body connected to the endocrine system via the use of metabolism - the same way larvae turns into an adult insect, but this time using the DNA of the original DNA and the virus' gene, which in this case is to do with / is wolf DNA. Lycanthropy is brought on by a large amount of bright Gamma Rays from a source, such as the moon, reflecting another source of Gamma Rays and multi-plying it by storing the heat before releasing it, the full moon is a perfect dose of Gamma Rays so it will start to take shape when a full moon casts upon a person with lycanthropy (a werewolf)'s skin.
Werewolves use their in-controllable wolf genes to catch pray that may not be necessarily eaten, therefore it could be classed as un-necessary deaths. But it is un-controllable in most cases, so it may be a little more different than murder.
Werewolves pratically only see edible living life as food, like any other ravenous wild dog or wolf. So they'd see anyone with any religion or even without in the same eyes.
When Gamma Rays lower their tone, as the moon sets or another light source constrasts out the Gamma Ray light source - the lycanthropy will settle down and slowly deplete the swelling in the endocrine system and bodily parts will become less wolf like and more human.
It has been knowledgable that you cannot remember what happened when being a werewolf as the same effect of drinking alcohol heavily is that to metamorphosis as it uses the same resources.
In films and other sources of mythology can blacken the truth of lycanthropy that is shown above.
Please note lycanthropy is now rare in urban areas as they have been cast out by torchlight sermonisers to get rid of the werewolves as they have been known to massacre.
See the realism?
Werewolf origin is actually unknown, but in folklore they are believed to have come from magic, yet the explaination of it is rabies - What they on? How'd you explain some of the sightings in real life of the spectrum - no technology for pranks back then, was there?
Well, I hope this improves your knowledge (as well as all readers)!
Thanks.
CybX Systems.
Excuse my English, It's not my main language.