In my world, the population of mankind has been all but wiped out by the accidental introduction of extraterrestrial plants brought to earth by scientists who were attacked by them. The plants reproduce by shooting seeds inside the victim at high velocity, and the seeds sprout inside, growing more of the aliens. These creatures can also move around like animals, and they're no bigger than a dog in size. How feasible would it be for such creatures to wipe out most humans?

The technology is that of slightly above modern era, in year 3005. Traveling to different parts of our galaxy is now a thing, although mankind only recently discovered such an ability.

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    $\begingroup$ Is one of them named Audrey? If not, then we are safe. imdb.com/title/tt0091419 $\endgroup$ Apr 7, 2021 at 17:13
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    $\begingroup$ That depends on many factors The Day of the Triffids $\endgroup$
    – Alexander
    Apr 7, 2021 at 17:16
  • $\begingroup$ Wouldn't the scientists notice all the seeds shooting out from all the plant-dogs running around during their "observation" phase of exploring that world? Also, as with most "doomsday" scenarios, you must rely upon deserve-to-die humans to do the hard work of crossing oceans, smuggling past quarantines, bribing guards, introducing to remote villages, etc. $\endgroup$
    – user535733
    Apr 7, 2021 at 17:36
  • $\begingroup$ I think you highly underestimate the actual stupidity of humans, which can be demonstrated in real life. And the Doomsday scenerio is direct result of the Doomsday, the first scientists aren't wise enough to know they're looking at the potential doomsday despite seeing it with their own eyes. (I don't want to go off-topic by giving examples) $\endgroup$ Apr 7, 2021 at 18:57
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    $\begingroup$ @NomadMaker There's an extremely popular theory that vaccines cause autism. Even very intelligent people somehow believe that! And Peter Duesberg, a revolutionary man and a genius, was the creator of the theory: AIDS is not caused by HIV, but rather by recreational drug use. 300,000 died from believing his stupidity. There's even a regular scientist who thought it was a good idea to let a rich arab's adult pet lion "play" with her, tackling her, and when it got off her she called it "a magical experience" (you almost died lol). Animals don't care if they're on tv... $\endgroup$ Apr 8, 2021 at 0:54

2 Answers 2

  • What is a plant, anyway?
    The definition has shifted over time. Multicellular organisms which derive energy by photosynthesis is one. Since photosynthesis is less efficient than eating food which (ultimately) derived from photosynthesis, plants tend to be immobile, but that doesn't have to be the requirement.
    Anyway, what we are talking about are alien lifeforms which some characteristics of plants. They're mobile, so talking about them as plants is misleading.
  • How do they attack?
    The aliens are capable of infecting human hosts at some distance, but they do not bring significant technology with them.
    As per your story, it might be that they do not bring culture and organization with them, either. That's assuming there is no such thing as "instinctive" knowledge of a language. And even if there are "instinctive" chains of command, similar to an insect colony or a herd of animals, I can't see how that works over intercontinental distances.

So summarized, we have rabid dogs that can turn humans into other rabid dogs with their bite. I'd say that they can put mankind into trouble, but not to the brink of extinction. Compare the current COVID pandemic. Yes, it is bad. Yes, many people died, and even more would have died without intensive care. Where the hospital systems were overwhelmed, fatalities skyrocketed. But it wasn't even close to exterminating mankind. And your plants are a lot bigger, easier to see and fight.

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    $\begingroup$ There's studies and sped-up videos that show plants reacting to their environment and even moving around/traveling and communicating, except much slower than most animals. I based this creature off of those plants, except it's full on walking. And I'd assume that they aren't full sized when they first exit the victims body, they'd be tiny hunters similar to baby gators $\endgroup$ Apr 7, 2021 at 18:40
  • $\begingroup$ @SuperYoshikong, moving fast requires much energy. Photosynthesis does not produce much energy, so plants move slowly. $\endgroup$
    – o.m.
    Apr 8, 2021 at 4:10
  • $\begingroup$ Pitcher plants climbing up and over trees like vines, and having a more carnivorous diet is a direct result of lack of nutrients in an environment. You don't think an environment could push a plant to be even more mobile and carnivorous? $\endgroup$ Apr 8, 2021 at 16:07
  • $\begingroup$ @SuperYoshikong, at some point calling a fully carnivore plant a plant becomes word games. You have alien lifeforms who had something like a plant in their ancient genetic history, but they are no longer plants as we use that word. $\endgroup$
    – o.m.
    Apr 8, 2021 at 17:48

The answer to your question is: Can be both 100% feasible and 100% not feasible or anything in-between as provided information is insufficient.

As o.m. said in their answer, the closest to your described situation would be a pandemic of some novel virus. You can use various epidemiological models to calculate possible scenarios for pandemic development. The most important factors to consider in your model would be:

  • plant physiology: If your plants are God-like heaven-defying organisms that cannot be poisoned, killed, or stagnated in any feasible way everything else does not matter unless the number of plants is very small and they do not reproduce;
  • plant reproduction (how often, how many seeds are produced, etc.): A plant that produces one seed in a century will not pose a threat even if it goes unnoticed, but a plant that produces 10 000 seeds every 2 days can overtake the entire planet in a matter of weeks or even days;
  • plant growth cycle (how fast the plant matures, what stages it goes through, etc.): a plant that grows and matures fast poses more danger than a slow-growing plant;
  • visibility of the plant (this is pretty much the same as symptoms of a disease): if your plant becomes detectable only when it is mature and ready to release seeds it is much more dangerous than a plant that makes a human grow leaves on their head;
  • viability of seeds outside of host organisms: If the seeds can survive outside hosts and can attach themselves to someone and sprout the problem is much worse than seeds that die fast without a host;
  • ability of humans to detect plants: If plants can be easily detected quarantine measures can be established easier than when plants are undetectable; the earlier plants can be detected the greater the chances of successful isolation of all infected from the rest of the population;
  • ability to contain the spread of seeds: How far the seeds are shot and can they be contained; isolation, necessary when dealing with infectious diseases, can be maintained only if transmission of infection can be contained and/or controlled;
  • social and political institutions and norms practised by humans: If humans are unwilling or unable to comply with testing for plants and quarantine requirements the situation will be much worse (e.g. compare the USA with S.Korea/Taiwan in the recent epidemic);
  • level of medicine: It is much easier to develop treatments for a disease when society reached advanced levels of medicine and has built all necessary infrastructure (hospitals, laboratories, research centres, manufacturing facilities, distribution chains, etc.).

In other words, treat your plants as an infection and then decide whether you want to kill your humans or not. The rest is just for decorum.


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