origins of vampires cut & pasted from vampires.monstrous.com

Mythology:
The first Vampire was Lilith, also the first wife of Adam that she eventually left for Lucifer. In short, the bone of the quarrel was that Lilith would prefer to stand over Adam but God wanted the man to rule. Lilith is also the Queen of Death and Demons. She was and is still adored in almost all religions by magicians, sorceress and witches.

The Hormone Theory: According to this theory, the vampire is the next step of human evolution. A genetic complex present inside our body but usually dormant get activated by a hormone brought in from an external source. The hormone transforms the victim's physical form and the new vampire will be able to inject the hormone into another victim.

The Fallen Angels Theory: This theory inspired from the Books of Enoch claims that vampires are the offspring of the union between the Watchers (Fallen Angels) and humans. When the Children of the Watchers had consumed all of the food available, they turned to mankind and began to eat their flesh and drink their blood. In another adjunct, vampires are the offspring of the daughters of Eve (female humans) and the Angel of Death sent by God on Earth. Vampires have the mission to control and thwart the demonic offspring of the fallen angels.

The Nanobot Theory: Nanobots, created either by renegade scientists or a race of reptilians, were introduced into a handful of human bodies in order to repair damaged cells. These nanobots performed so well that they rendered their hosts immortal. However, the Nanobots themselves are not immortal and must self-replicate by utilizing the iron atoms from the hemoglobin in the host's red blood cells. The result of this nanoreplication process is the constant need for sufficient supplies of blood. Unable to keep up with the demand, the host has no choice but to seek out blood from others. If the colony of Nanobots exceeds the host's ability to supply sufficient RBCs, some nanobots may migrate into another host, usually the next victim of the primary host's bite.

The Atlantis Theory: The Atlantans, in their quest to prolong life, have conducted biological and genetic experiments which end result was a new human that could live for centuries but had to drink the blood of humans in order to survive. Vampires have escaped the Great Flood as the Atlantans, not satisfied with the results, had buried them in an underground crypt.

The Alien Vampire Theory: Since H.G. Wells' "The Flowering of the Strange Orchid" in 1894, there has been many writings and movies exploring the possibility of a space alien taking over a human body in order to live off the life energies of others. Those space aliens are some kind of parasites that control our mind and draw our vital forces. When they have exhausted the body, they look for a new host. In another adjunct, vampires do not come from outer space but from another dimension.

Etymology: The word 'vampire' derives from the Slavic word 'vampir' or 'vampyr', first appearing in the 1600s in the Eastern European region in the Balkans. 'vampir' is derived from 'upir', which first appeared in print in an Old Russian manuscript from 1047 AC in which a Novgorodian prince is referred to as 'Upir Lichyj' (Wicked Vampire). But the origin of 'upir' is even more controversial. Franz Miklosich suggested that 'upir' is derived from 'uber', a Turkish word for 'witch' whereas Andre Vaillant suggests just the opposite. Kazimierz Moszynski suggests that 'u-pir' is from a Serbo-Croatian word 'pirati' (to blow). Aleksandr Afanasev points to the Slavic 'pij' (to drink), which may have entered the Slavic language from the Greek, via Old Church Slavonic. A. Bruckner proposes Russian 'netopyr' (bat).

Diseases linked to Vampirism: Xeroderma Pigmentosum (XP), meaning pigmented dry skin is a rare, often fatal genetic disorder that leaves its victims acutely vulnerable to skin and eye cancers if they are even briefly exposed to sun or any ultraviolet rays. The body fails to produce one of the enzymes necessary to make heme, the red pigment in hemeglobin. Strangely, Garlic stimulates heme production (a reason for its inclusion in many herbal blood tonics) and can turn a mild case of porphryia into a severe and painful one. There is less than 100,000 identified cases of XP nowadays but inbreeding could have stimulated the disease in the middle ages, creating pockets of it in isolated areas. Drinking blood could have been considered as a remedy in the dark ages but the human body is not made to assimilate heme directly from blood so it cannot be a cause of vampirism.