When did vampire folklore start?

Answer 1

It largely depends on what you consider Vampire Folklore. Almost all ancient cultures have some form of "demonic" creature who consumes human blood. Many cultures also had gods who required sacrifices in form of blood, but let's not count those for now.

Hebrew texts speak of Lilittu, a screech owl like crature that consumed blood. Ancient Mezoamericans had all sorts of creatures who drank blood, the only human looking ones though had a fanged skull instead of an ordinary human head (though were largely human in every other way). Ofcourse, this is streaching the definition of Vampire a bit.

If you refer to the folklore about humans returning from the dead to drink the blood of the living, then it is slightly more recent (note the term "slightly").

In Asia there was the belief in the existence of the Jiang Shi, which were animated corpses of the dead whose souls did not leave their body (curiousely enough, the "mind" did leave). These Jiang Shi needed to consume "life energy" or "Qi" to continue being animated and thus "hopped" around looking for it. The main means of obtaining Qi ofcourse was through the consumption of the blood of the living.

In Europe, many myths about vampires existed, each differing in how they came to be, how they behaved, what they looked like and how to despach with one. As the Roman Empire expanded, it took with it bits and pieces of folklore that would (just like the language of the romans) combine with local folklore to create new versions of old favorites. Personally, this is where I would say the folklore about vampires began, because it is from this period that we find the roots of the currently known vampire. Bear in mind that the expansion of the Roman Empire was through military efforts, which means that contact was made through legions of soldiers. Both in antiquity as in modern times, soldiers have a tendency to be "ritualistic" and thus incorporate easily to their belief system what ever they come across. If you were a soldier invading an unknown land and heard about a "haunted" place you would probably take it at face value, and so then it is easy to see how folklore begins to entwine and overlap. More so when you know that soldiers are known for their bragging and storytelling at the campfire.