The hybrids were created when unseen aliens sent SETI a message explaining how to combine human and alien DNA. (Ignoring the scientific illiteracy and contradictions in the films) Under the constraints of real science, how could an engineered alien-human hybrid organism approximate the traits of the hybrids in the films?

These traits, off the top of my head, include:

  • accelerated growth and aging: Sil grew to adulthood in under a month, Miranda was dying of old age after a few years of life.
  • shape shifting: the hybrids look like Giger monsters with claws and spines and tentacles but may assume an externally human appearance.
  • excel at observational learning: Sil learned to speak conversational English in a few days, Sara and Miranda could instantly read books in a few seconds.
  • sense genetic abnormalities in potential partners: Sil could determine a man had type 1 diabetes, Eve could determine a man was a carrier for sickle cell anemia, Miranda could determine another hybrid was sterile.
  • heightened and unusual senses: Sil in the novel mentally perceived toxic gases, good smells and pheromone signals as colors.

EDIT: additional traits after some researching:

  • genetic message in a bottle: Sil would experience dreams that included subliminal messages from whoever provided the alien DNA that impelled her to reproduce, Eve broke out of containment to seek another hybrid partner after learning of his presence, Miranda experienced psychotic episodes as she began dying of old age and then became murderously horny after receiving stem cells to reverse her aging.
  • no innate conscience: Sil was raised in a glass box with little human contact and killed anyone who got in her way, Eve was taught morality and attempted to stop a mass murdering psychopath, Sara was taught morality and refrained from killing except when under sexual assault, Miranda was taught morality and only committed murder while experiencing abnormal psychotic episodes.
  • $\begingroup$ Note that this can get complicated. The gene for sickle cell anemia is hardly a genetic defect. In malarial areas (with long-term historical medical knowledge - that is, none) it acts as a strong survival trait. In the long term It is only a problem where malaria isn't. $\endgroup$ Commented Sep 28, 2016 at 23:45
  • $\begingroup$ Innate conscience... don't think that even humans have that. Ever seen an innocent kid tear legs off an insect? It's a sobering sight, making very clear how much of an innate conscience we don't have. Humans have to learn their morals too. We only start out with some empathy by default, and that is easily dismissed towards those who are of a different species, race, gender, religion, et cetera. For us it's normal to make a difference between steak and murder, so why should the hybrids not? It could even be that their cruelty is not part of the alien side, but comes from them being part human. $\endgroup$
    – Estharon
    Commented Oct 3, 2016 at 12:24

2 Answers 2


Go trait by trait.

accelerated growth and aging:

There are a few known diseases that result in accelerated aging...DNA repair deficiency disorder for example. Werner syndrome is another example, however they still live for more than 40 years on average. This is an extreme case of it (aging and dying in less than 2 years), but there is some known background to it. Look up Progeroid syndromes for more info here.

shape shifting: the hybrids look like Giger monsters with claws and spines and tentacles but may assume an externally human appearance

This one is much harder to resolve without going out into pure speculation. Mass conservation tends to be one issue as they change sizes and concealing weapon grade traits like giant claws isn't an easy feat. The best explanation I can offer here is somewhat inspired by the movie 'Lucy'. In the end, your body is a mass of cells that you have some control over, but not much. If you could command your cells to take new shapes and new configurations, then you could potentially get some shape change ability supported at a cellular level. Reeeeeeacchh, but maybe?

excel at observational learning: Sil learned to speak conversational English in a few days, Sara could instantly read the entire contents of a book by touching it

Humans are quite good as is at early language acquisition to the point where it's been proposed that the early child has a specific mental 'device' called the early language acquisition device (theory proposed by Noam Chomsky, google it) that is dedicated to learning a new language. Assuming a much more efficient brain...2 days is still quite short, however it is in the range of plausible since we don't understand much on the subject.

Touching a book to read it's contents is a bit further out there...page flipping extremely fast is a little more justifiable.

sense and understand genetic "disease" in potential partners: Sil could determine a man had type 1 diabetes, Eve could determine a man was a carrier for sickle cell anemia

There is a particular book called 'Tannion' that has similar story involved...the main character finds himself capable of knowledge on a cellular level (perhaps Lucy is another movie reference here as well). Though this knowledge is initially focused on himself, he eventually finds himself capable of reading other peoples cells (through touch) and this information is readily held in each persons cellular structure. Feasible? probably not, but within the range of existing fiction anyway.

heightened and unusual senses:

Our senses actually pass our brain much more information than it's capable of processing. If you want the IT comparrison...our eyeball and the optic nerves as streaming data to our brain in the gigs per second range while our brain is processing it in the KB per second range and this is true for other sense as well. One would assume if the brain was the bottleneck, an increase in brain processing power would make further use of the senses we do have.

There is also Synesthesia where our brain relates things to senses (such as letters and numbers are directly related to a colour, or time (months) are associated to a colour, or even numbers are related to genders). Perceiving anything to a colour is a known trait now...expanding it to toxic gasses and other inputs isn't that far of a stretch.

Kinda funny that the only one I can't justify in the least is the book reading through osmosis...anything else has some potential.


I don't really see a problem with Hybrids growing and aging faster than humans. Creatures exist on this very planet that grow faster than humans, so it's not unreasonable to think that an alien species or human-alien hybrids could have a faster growth and/or metabolism rate. They are not really human, so why would our traits apply to them?

The transformations and their actual defiance of physics are mostly a question of mass vs volume. Short of weighing the hybrids, it's hard to tell if they really gain mass. The only thing they obviously gain is volume.

So, what's the easiest way to change volume? Deflated structures, inflated by a liquid that boils slightly above normal body temperature. The body heats up a bit, steam expands the deflated structure, maybe a few hardening chemical reactions here and there to make those claws and spikes useful, and voila, enough tentacles for all your weird feti- ehmm... horror movies.

Smelling disease: We are also able to smell sickness to a degree, the metabolic imbalances it causes alter the smell of a person. However, we're not used to rely on that ability. To give a relatable example, even the most civilization-numbed people are able to recognize the smell of old people, or children. Both Diabetes and Anemia would affect the metabolism, so it's possible that the hybrids just have a fine enough sense to notice the different smell. Also, dogs. They do pretty much the same thing portrayed in the movie, but on an instinctive level. They're just not smart enough to give a detailed diagnosis of specific diseases, as Sil and Eve would.

Twelfth did a good job on some of the traits, and I don't feel like writing redundant info, so props to them for the answers regarding superhuman senses and mental capabilities.


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