You might need to sit down. I'm serious, I think I may have cracked this thing wide open.
You've probably wondered where the idea of vampires came from. "Perhaps," you thought to yourself, "the idea came because vampires exist." Or maybe you thought: someone saw a bat and thought, "Wait, what if that were a person?"
But I'm here to tell you that the whole vampire myth (or reality!) came from one place: teenagers.
Hear me out (why are you running away?). Consider your 11- or 12-year-old child. Happy. Cheerful. A pain in the ass, maybe (like the rest of us), but recognizable to you. Then one day…everything changes. The child retreats to his room, far from the sun and any contact with you. Where once he woke you up regularly at 6 a.m. (which was, admittedly, a bummer) now he sleeps till 11! Noon! Even later! When he emerges, surly and pale, hungry for meat. Or cornflakes—whatever, let's not quibble. A pervasive aura of gloom covers him, until nightfall. Then, he perks up, energized, wanting to go out into the darkness, to wreak havoc! Or go to the movies (note: also in the dark!).
It all makes sense! All those studies, "Teenagers have different physiological needs, and are at their most productive from the hours of 9pm to 2am." Why did we never fully understand the signs before? They retreat into their dark lairs, and emerge, pale, taller, and sexualized. All that's missing are the capes! And sometimes the capes are even present!
OK: admittedly, I haven't fully figured out where the whole drinking blood, killing, stake in heart aspects come into play. But mark this, oh doubters. When did Bram Stoker write Dracula? 1897. When was his son born? Oh, 1879—so he wrote it when his son was 18 (yes, I can google and add and subtract with the best of them). He had spent the past years researching vampires. Why? Because he was living with one.
Further evidence: consider that other literary masterpiece, Zagazoo.
I have now solved the primary riddle of existence. Now I must eat lunch and work out that whole middle-east thing.