A parasite starts its first stage of life with the reproductive phase by cloning itself to infect as many people as possible without leaving any signs of its presence.

After two days, the parasite starts its growth phase during which it controls the brain of the victim, making it a zombie wandering around, searching for a safe place in the darkness, where it will start to cover itself in a cocoon.

Inside the cocoon various parts of the zombie's body will be absorbed and recreated in a different form.

Then the pupa will grow into an adult vampire that would still have almost the same external appearance as the previous zombie/person, but with subtle differences in bone structure, muscle mass and a slightly bluish or pale white skin depending on the individual. The human-like appearance is used to fool other non-infected people into thinking they are not vampires.

A vampire has increased intelligence, strength, and stamina, the vampire doesn't need to relearn everything, having some essential memories of the previous human that include language, clothing, basic tool use, and geographic memory.

The vampire doesn't demand a lot of food, but after the cocoon phase it will be hungry. It will start to search for the zombies that didn't start their cocoon phase yet and eat them; if there aren't any the vampire will start to hunt humans and drink their blood while infecting them at the same time with the parasite to repeat the cycle.

The vampires can reproduce sexually and skip the parasitic phase, but they still prefer to infect other humans because both blood and zombies are great sources of food and don't require taking care of vampire kids as zombies metamorphose directly into adult vampires.

In the event that a vampire doesn't find any zombies or any people around, it will start to drink the blood of other animals or eat plants. It can only digest zombie meat, mammal blood and plants.

Other features of the parasite:

  • The adult vampire doesn't get stronger and smarter with age
  • The adult vampire doesn't have a lifespan limit
  • The vampire can regrow its head if decapitated, but not other limbs
  • The vampire has its brain in a boned box inside the chest
  • Zombies can't talk and they move incredibly slowly, with bad coordination
  • Vampires don't sleep, but enter rest phases in which their activity is diminished
  • Vampires can see in the dark
  • Vampires are cold blooded for the majority of time, but can become warm blooded when needed to do so

My questions are: How did this vampire/zombie parasite come to exist? Why does it have so many features that are useful for individual survival, but have no apparent reason to evolve in the first place? Also, what explains its diet of eating blood, zombies and plants but not the flesh of humans and animals?

  • 1
    $\begingroup$ This is far too extreme to have evolved on Earth given our understanding of evolution. There was an edutaintional YA novel some years back titled "Peeps," which presented vampirism as parasitic infection in a far more grounded fashion. If the YA target doesn't drive you away, you might enjoy it. $\endgroup$
    – Anonymous
    Commented Aug 22, 2016 at 12:51
  • $\begingroup$ It can turn from cold blooded to warm blooded?? It can regrow its head? Effectively making it immortal if regularly provided food? And then the problem that it seems to have adapted to hunt humans, animals that hunted humans are usually killed fast. And in order to evolve to the stage you described, it would take multiple generations of successful human hunting without anybody noticing to turn from whatever it was to this. $\endgroup$
    – Skye
    Commented Aug 22, 2016 at 12:58
  • 1
    $\begingroup$ Scientifically, blood is a very poor source of protein and nutrients. I believe we have a question about that somewhere... $\endgroup$
    – Jax
    Commented Aug 22, 2016 at 15:10
  • $\begingroup$ Here... $\endgroup$
    – Jax
    Commented Aug 22, 2016 at 15:14

2 Answers 2


Maybe the parasite didn't evolve in people.

As another post mentions, it would take a very, very long time for a parasite to evolve in such dastardly ways, and through all of human evolution, you'd think someone would have noticed this phenomena. Even assuming the zombie/vampire numbers are rather small, enough humans would see and survive zombie/vampire encounters and would begin to hunt down and exterminate the parasite responsible. Yes, some of the infected might survive the initial sweep, but people would start working on antibodies and vaccinations.

Clearly, this hasn't happened, so the zombie/vampires must not be so systemically linked to humanity. There are several types of mind-hacking parasites out there already. Some attack mice and rats, others fish, others ants. With all the interactions between humans and animals, especially all the kinds of animal that we kill, it seems quite plausible that somewhere along the way some people might be exposed to a new kind of parasite, one we don't know about because it doesn't usually infect humans.

This parasite, having evolved to take over the brains and bodies of a different animal, is clumsy in its human host, hence the poor motor control and loss of ability to speak. The parasite, which would normally induce its host to seek out its predator, guides the zombie to a safe location while it adapts to its new and vastly different environment; the human brain.

The parasite begins to re-form its host as soon as it enters the blood-stream, seizing control of muscles and nerves as it makes its way to the brain. Within a few moments of a bite, the human is merely a host. Within a few hours, the parasite is beginning renovations on a large scale. The parasite is in unfamiliar territory, so it seeks to make the human more like its intended host. The first step is to discard all the various proteins and chemicals that the parasite is unfamiliar with. These are expelled, sometimes violently, as cysts and abscesses on the skin of the host. When these burst, the contents mingle and form a sort of cocoon.

The next step is for the parasite to get the body in working order. This could be likened to the owner of a new house rearranging the furniture; the outside of the house looks the same, but the inside has been changed to suit the new occupant. This explains the brain being moved into the chest, as well as the newfound strength and speed of the emerging vampire. Because this process occurs in a dark space, the parasite installs a tapetum lucidium (that layer that makes cats' eyes glow), allowing it to see in the dark.

The vampire, now fully formed, emerges into the world with most of its functional memories in tact. Having spend a few days reforming its insides, as well as expelling large quantities of fluid and material, the vampire is hungry and seeks a meal. Its first choice is a zombie because not only does a zombie contain exactly what the newly ex-zombie needs, but it is slow and easy to catch. Additionally, the parasite has reordered the human digestive system, drastically weakening it. Any normal food, even raw hamburger, is too tough for the parasite's new digestive system to handle in anything like an acceptable time, so the vampire seeks out predigested food. In the zombie stage, the parasite is reordering things on a cellular level, so zombie flesh is already broken down, requiring very little effort to digest.

Failing to find a zombie, the vampire turns to the humans around it. The parasite can now be found in any part of the host body, including its saliva, so any human that is attacked and then abandoned will be infected. The fact that the parasite begins to take control of the host's nerves as soon as it enters the body accounts for the mythological "venom" that may numb or paralyze the victim while the vampire feeds. The parasite requires massive amounts of iron to survive and function which is why the vampire has an intense craving for blood. Most of the nutrients in blood are negligible in terms of energy intake, but blood contains iron in concentrated form, making it essential for the vampire. Because both zombies and vampires closely resemble humans, the parasite is attracted to humans over animals, perhaps confusing the human for a zombie.

Failing to find humans, the vampire will slake its thirst for blood with animal victims as their blood is little different from ours. If there are no animals nearby (which seems unlikely seeing as the parasite had to get into the human from something), the vampire will resort to feeding on plants. There is no nutritional value in the plants, but the vampire is famished and desperate. If there were no plants, it would eat rocks, however, just as a human becomes hungry long before he is in danger of starving, the vampire can survive for several days without food, even after it metamorphoses, because the parasite has stripped the host body of most of its energy-consuming processes. Blood-flow is diminished except during strenuous activity, and the parasite has cut most metabolic function, resulting in the 'cold-blooded' resting state. If needed, the parasite can kick-start the metabolism, allowing the vampire to survive in cold weather. In addition, the vampire need never sleep, seeing as sleep is mostly a chance for the mind to process what happened in the day and the host's mind is not really processing anything anymore. The body's need for rest is met by phases of low activity.

In summation: The zombie/vampire parasite displays the expected self-preservation drive but not the species-preservation drive because, since the parasite didn't evolve to live in humans, the parasite does not accurately identify the hosts its own species. The vampire consumes zombie flesh because its weakened digestive system cannot handle flesh that is not pre-broken-down, as is the flesh of a metamorphosing host. Humans remain unaware of this parasite because very few humans are infected and survive.


Assume that the ancestor of this vampire/zombie parasite was a brain parasite that ultimately consumed the entire body of its host and it parasitized early hominids, but the early hominids were good at detecting its presence in the infected.

This has the effect of subjecting the parasite to strong selective pressures. Forcing the parasite to develop more and more mechanisms to conceal its presence in hominids and later in humans. Somewhat like the Eumenides wasps it would have progressively developed ways of first taking control of its host's body. Eventually developing virus-like mechanisms for hijacking host cells to undergo metamorphosis into what would become the adult vampire stage of its life cycle.

The adult vampire would retain the capacity for metamorphic regrow, so the loss of vital parts could be replaced. All the traits of the zombie/vampire creature will have arisen from natural selection due to the evolutionary arms race between host and parasite.

Presumably the zombie stage has poor coordination and a lack of speech because the parasite has taken control of the motor cortex of the host and inhibited other parts of the brain that might interfere with its dominance of the host.

Its dietary requirements may have evolved simply because trying to devour uninfected humans would be a clear signal that this wasn't a normal human being but a zombie/vampire.

On a more cautionary note: for a remarkable parasite of this kind to have evolved, because if it didn't evolve it would need to be engineered and while that would be simpler explanation it does open a lot more awkward questions, it would take an extremely long time. There are a considerable number adaptations that would have to develop and that can only happen with a lot of time to do so. This is only a guesstimate: probably several hundreds of millions of years. Basically much longer than the complete history of human evolution. This suggests it mainly happened somewhere else where there was more time for it to do so.

  • $\begingroup$ Any chances the parasite could survive with its human body speared or any other method to kill? $\endgroup$
    – Skye
    Commented Aug 22, 2016 at 13:00
  • $\begingroup$ @Sky With a parasite this exotic, anything is possible. $\endgroup$
    – Jax
    Commented Aug 22, 2016 at 15:16
  • $\begingroup$ @Sky Its brain is in its chest, admittedly inside a relocated skull case, driving something through that should be fatal. $\endgroup$
    – a4android
    Commented Aug 23, 2016 at 4:54

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