Parasites cannot evolve
Parasites exist in all stages and forms of life. There are smart and primitive ones. Primitive ones take out energy until the host will not die out completely. In this case primitive parasites live short range life. Smart ones let the victims exist for the longest interest of theirs, since they totally comprehend what will happen if the host dies. From this point smart parasites evolve to the very point where they have to switch to the creative force.
If they are able to. Usually it happens when spirits convert to the human forms of life. They start to create. They start to comprehend of what is happening around them. But this happens only when they sacrifice their abusive nature. However, there are parasites exist among people as well. It is those people who cannot or don’t want to bother themselves pasting themselves on creative force. Usually it is old people and genetically spoiled. But not all of them. Some people adapt to suck out the energy out of others.
They need to talk to someone, to be close, to feel the energetic bridge from the victim. And it is obvious, they are on their ways off. After some interaction with donator they feel great. But just for a while. Until they need more energy. As a result, the prey feels completely exhausted. Stay away from such individuals. Do not communicate with vampires for the sake of own convenience. They are parasites. Because, never been taught on how to stay human.