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In my world, the characters have to travel to a new planet and start all over again. Say they make the journey in a space ship transporting a bunch of human DNA samples. If this ship crashed on the new planet, everyone died, and the DNA "leaked" onto the surface, could anything come of it?

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    $\begingroup$ If possible it would take billions of years to develop a living creature $\endgroup$ – Yacomini Sep 12 '16 at 13:36
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    $\begingroup$ Well, that's not going to work. Where would you get the oxygen to make a planet hospitable without life to reduce the carbon dioxide? It took life to make Earth hospitable - the conditions where life appeared were nothing like where humans can survive. $\endgroup$ – Luaan Sep 12 '16 at 14:33
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    $\begingroup$ Well originally I was just curious if it would work with DNA but now I'm regretting the wording of my question and considering writing a new one. I am indeed curious about how to make it work. $\endgroup$ – Matthew Goulart Sep 12 '16 at 15:31
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    $\begingroup$ @JDługosz good point I hadn't thought of that. $\endgroup$ – Matthew Goulart Sep 12 '16 at 17:02
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    $\begingroup$ This reminds me of the opening scene in Prometheus. $\endgroup$ – aroth Sep 13 '16 at 13:28

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Just DNA? Probably not.

DNA in and of itself is just information. It contains the coding for cellular machinery, it is not that machinery itself. In the case of a crash landed ship where all humans have died but left the hull largely intact, then all the bacteria, microbes and fungi would spread out from the hull and start populating the planet. Give it a few billion years and there might be human like things walking around again.

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  • $\begingroup$ So the result may not necessarily be humans? Is there anything that would fit the scenario that would GUARANTEE that humans would eventually re-appear? $\endgroup$ – Matthew Goulart Sep 12 '16 at 13:39
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    $\begingroup$ @MatthewGoulart, no, there is no way to guarantee the reappearance of humans or even human like things on this world. Using the power of the Author, it's possible but in real life, no. Evolution is chance and luck. Earth saw about 176 million years of crazy diverse life (the dinosaurs) without a human form. $\endgroup$ – Green Sep 12 '16 at 13:47
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    $\begingroup$ For one of the best explanations I've ever seen as to what it takes to evolve a human (and why humans look the way they do), I'll point you here: worldbuilding.stackexchange.com/a/2496/10364 $\endgroup$ – Green Sep 12 '16 at 13:50
  • $\begingroup$ That's a really good answer! Thank you for pointing it out. $\endgroup$ – Matthew Goulart Sep 12 '16 at 14:02
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    $\begingroup$ @NuWin: No, you wouldn't know, you would have just relocated the question of the origin of life to a different planet. $\endgroup$ – jamesqf Sep 12 '16 at 17:35
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There are some bacteria on Earth capable of transformation. They can take up DNA from the environment and incorporate it into their own genome.

When such bacteria also exist on the alien world, they might end up with traces of human DNA. When these bacteria then evolve into higher lifeforms over the next millions of years, traces of the human DNA might still be detectable in them. It is very unlikely that the resulting lifeforms will have any obvious resemblance to humans. But when someone analyzes their genome in a lab, they might be surprised to find a few genes usually only found in humans.

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    $\begingroup$ I really like this (and similar) answers because a reader could technically not categorically deny the possibility of an almost identical species to humans developing as a result. Especially when you take into account the wonderful answer here worldbuilding.stackexchange.com/a/2496/10364 ( originally posted by green in this very question) $\endgroup$ – Matthew Goulart Sep 12 '16 at 16:49
  • $\begingroup$ I'm choosing this as the answer because it most directly addresses my question (the way I was hoping for). However, some other answers are also very informative. Overall, everyone is a winner in my books :) $\endgroup$ – Matthew Goulart Sep 12 '16 at 16:51
  • $\begingroup$ @MatthewGoulart If you've found this answer most helpful you should consider accepting the answer. $\endgroup$ – Erik Sep 13 '16 at 14:46
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    $\begingroup$ Because the microbes on the alien world evolved independently, this answer assumes that DNA is universal to life. Can't even call them "bacteria" because that implies they're on Earth's evolutionary tree. $\endgroup$ – Schwern Sep 13 '16 at 17:47
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    $\begingroup$ @MatthewGoulart "could technically not categorically deny the possibility of an almost identical" that's a lot of hedging! Technically, I cannot categorically deny the possibility that I will be hit by a meteor today, doesn't mean I'm wearing a helmet. ;) No, because some bacteria picked up a few hunks of human DNA (not whole strands, just carved off some pieces) its descendants will not be humans. Your DNA is about 8% virus. Your descendants will not be viruses. $\endgroup$ – Schwern Sep 13 '16 at 17:55
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Consider how much infrastructure a human being needs to survive and grow up before it gets self-sustaining. Even if you had a cell to begin with (more than just the DNA), you would need a womb, a mother to take care of the child as it develops, supply it with nutrients and teach it to survive, and maybe in a few years you'd have a working human. Your scenario is more ridiculous than expecting that a bit of your dead skin would come to life as another human :)

If you want an analogy, it's kind of like expecting that if you throw a floppy disk at the ground which contains a Word document, it would get printed on sheets of paper. You're missing all the machinery required to make that happen.

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    $\begingroup$ What is a floppy disk? $\endgroup$ – NuWin Sep 12 '16 at 15:41
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    $\begingroup$ @NuWin It's like an eight-track reel-to-reel tape, but all bundled up and a lot more convenient to use. $\endgroup$ – a CVn Sep 12 '16 at 16:49
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    $\begingroup$ Great, the wet-behind-the-ears brigade has moved beyond “what’s a record?”. $\endgroup$ – JDługosz Sep 12 '16 at 17:06
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    $\begingroup$ @wizzwizz4 I don't know what Retrocomputing's policy is on those (I mostly read, there; haven't found many questions where I've been able to contribute an answer, and most of those had already been well answered), but even with much more to it than in NuWin's comment, that's the kind of question I would downvote for lack of research effort. Even the most cursory perusal of Wikipedia would answer it, in excruciating detail. $\endgroup$ – a CVn Sep 12 '16 at 17:07
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    $\begingroup$ @MichaelKjörling Perhaps it's a few decades too early for that question to appear... $\endgroup$ – wizzwizz4 Sep 12 '16 at 17:43
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You are essentially asking if abiogenesis (life arising from non-life) could be catalyzed by the addition of DNA. The answer is we don't know, because we aren't sure how abiogenesis works.

It definitely might help though. Most models of abiogenesis start with the creation of organic building blocks, such as nucleic acids which make up RNA and DNA. Then these building blocks arrange themselves by chance into some sort of self-replicating polymer. This then begins the evolutionary march as those self-replicating chemicals mutate and procreate. A big influx of organic building blocks in a concentrated area, if the conditions are near perfect, could kickstart the beginnings of life. But, it is a long shot.

One note is that DNA is actually not that great at forming self-replicating polymers and it is widely believed that the first life on Earth was based on RNA because it has better catalytic capabilities. You can read more about it here. So it may not actually be the DNA from your humans that begins life on the new world, but rather the RNA.

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The mad genius scientists which planned the colonization mission came to the conclusion that those colonists who volunteered for the mission might be great for flying through space and building a colony, but would be unworthy to be the genetic base for the new human population. They picked a number of far more capable specimens of mankind. But how would they spread their DNA to the planet?

They came up with a devious plan: They bio-engineered a new retrovirus. A retrovirus is a virus which latches on to cells and replaces their genom with its own. But their retrovirus had some modifications: It carried the DNA of the "worthy" humans, and it only targeted human egg and sperm cells. They filled a vial with that virus and planned for it to burst after landing on the planet. The idea was that all the colonists would be contaminated with the virus and all their children would not be their own genetic offsprings but those of the chosen people.

They expected that it would take the colonists a couple years to notice that all the children born on the new world have no genetic similarity with them and then at least a decade until they found the reason and purged the retrovirus. But until then there would be plenty of retrovirus-children around and disowning them would be both immoral and impractical. So the children would assimilate into the society, have children themselves and carry on the "superior" genes.

Unfortunately nobody will ever know if that plan would have worked because those genetically inferior colonists couldn't find the "activate parachute" button in time.

But curiously that retrovirus worked too well. It didn't just work on humans but also on the local fauna of the planet. So all creatures around the crash site started to become pregnant with human babies. Most of those embryos would not survive gestation in an uterus designed for a completely different species. But there was one species which was for some crazy coincidence biologically compatible enough with humans to give birth to living human babies and socially compatible enough to keep them alive during infancy.

Note that especially the last part is very unlikely, so it will require quite a lot of handwaving.

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  • $\begingroup$ Very creative! Unfortunately the mad scientist doesn't quite fit in with the narrative. I do, however, like your idea of a retrovirus. With some tweaking, it could be the solution. $\endgroup$ – Matthew Goulart Sep 12 '16 at 13:59
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    $\begingroup$ The species that is so compatible is sentient and recognized what was happening because that's how they themselves had populated this world just a few centuries back. :-) $\endgroup$ – SRM Sep 12 '16 at 14:51
  • $\begingroup$ @SRM Centuries from the perspective of the generation ship. Millennia from the perspective of the planet-bound rest-of-species. $\endgroup$ – wizzwizz4 Sep 12 '16 at 16:57
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Yes, if there was bacterial contamination in the vial. The human DNA won't do anything, but any bacteria that are in the vial might manage to survive and reproduce.

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Everyone died in the crash - but millions of species of bacteria in the bodies, food system, and on rocket surfaces survived? Most of them require oxygen for life (which is not yet present on your new planet) but few do not, and those will take over the planet.

In few billions of years (and with some luck) you will have more habitable planet.

The vial with DNA is 100% irrelevant, especially if it is human DNA.

To improve your chances, and speed things up, you should aim to sending an fully automated rocket which will orbit the planet for few hundred millions of years and send down (soft landing, not burning on entry) capsules with bacteria needed for next evolutionary step: anaerobic bacteria first, then some algae to produce oxygen, later some hardy multi-cellular organisms, to give evolution some shortcuts.

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  • $\begingroup$ I like the idea but perhaps I went too far in saying the planet is in the "early stages" Let's assume the planet already supports basic life. $\endgroup$ – Matthew Goulart Sep 12 '16 at 16:54
  • $\begingroup$ @MatthewGoulart - Please define "basic life". Are oxygen-creating bacteria present? What is level of oxygen? What about multi-cellular organisms? Plants? Life outside of the oceans? Regardless, a vial of DNA will do you no good. It is not alive. You need living, replicating life-forms. $\endgroup$ – Peter M. Sep 12 '16 at 17:23
  • $\begingroup$ Honestly, the exact state of the planet is not terribly important. If the only way to make this plausible is for there to already be life, oxygen and plants, then so be it. I posted a different question that you may enjoy answering more than this one: worldbuilding.stackexchange.com/questions/55087/… $\endgroup$ – Matthew Goulart Sep 12 '16 at 17:25
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Luaan is utterly correct in his/her assessment, as DNA is only a set of instructions that encode a design. If a womb were not available, then the theoretical minimum that would be required would be an artificial womb, equipped with an artificial connection to the umbilical chord (starting at a microscopic scale), accompanied by an artificial input of blood, into which would have to be added a regular, frequent supply of nutrients (in a manner equivalent to what is provided by a stomach) - plus a constant supply of oxygen via the very same route.

Even were all the above possible and successful, and the resultant child were successfully 'born', it would then need constant nuture in the form of artificial feeding, cleaning, protection, nurturing and training.

Seeing as all of the above are outlandishly far-fetched, the bare minimum requirement would in reality be one human being aged around 8-10. And it goes without saying that male and female would be required for there to be any continuation.

As for abiogenesis, that is even more far-fetched than the above scenario. Non-animate materials remain non-animate materials that decay, in line with the second law of thermodynamics. Life requires an intelligent blue-print (which is what DNA represents), along with a suitable environment, plus an ability to survive and reproduce.

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    $\begingroup$ "Life requires an intelligent blue-print (which is what DNA represents)" Um, no. I'm not aware of any scientifically accepted theory that puts life's origins on any planet in the realm of intelligent design, and I very much doubt that such a theory would gain much ground seeing how well-received any concept of intelligent design would likely be in the scientific community; existing theories explain well the available data, and require far less handwaving. See Occam's razor. I was about to vote this up for discussing the requirements for procreation, but that last sentence changed my mind. $\endgroup$ – a CVn Sep 12 '16 at 16:55
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DNA alone, certainly not. However, a vile full of single cellular organisms (complete cells) certainly could survive as long as they were able to adapt to the environment.

A multi-cellular organism generally requires a parent for birth and nurturing. However, this does not have to be the case. It could be possible for an advanced culture to create a stem cell which would grow up on its own into a multi-cellular creature without the need of a parent. I can't think of a creature currently in existence which has this ability.

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  • $\begingroup$ There are lots of relatively advanced multi-cellular organisms which abandon fertilized eggs to unparented chance. Trees and oysters release somatic cells to chance hoping they will meet a compatible partner, and they are wildly successful multicellular species, at the extreme end of the r/K spectrum (en.wikipedia.org/wiki/R/K_selection_theory) . Most reptiles hatch from unattended eggs. You could easily handwave your way to something as complex as a platypus being seeded from unattended eggs. $\endgroup$ – arp Sep 14 '16 at 16:03
  • $\begingroup$ I agree eggs would be able to hatch and survive on an alien planet. Eggs are sort of an intermediary parent. They are a complex multi-cellular organic incubator. The vile of liquid could contain eggs. $\endgroup$ – Jason Williams Sep 14 '16 at 16:25
  • $\begingroup$ The problem is that the incubator (egg) is a reproduction feature that was adapted to one environment, and dropping the eggs to hatch on a new planet does not prepare the host to the new conditions. Unless the new planet is VERY similar to the original one in atmosphere composition, pressure, gravity, etc, there is very little chance any specimen would survive, much less reproduce. You need to bring the DNA in a matter that it can then go through evolution with the specific conditions of its habitat. Start small, virus or bacteria small. $\endgroup$ – Drunken Code Monkey Oct 8 '16 at 4:32
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Presumably, the goal was to repopulate to begin with, so if we assume the DNA collection is transported via live retrovirus (DNA sequence encoded in RNA, once the virus infects a host, it starts reproducing from the DNA it is programmed with) AND that there is already life the virus can infect, AND that some of that life is malleable enough that it doesn't die upon infection, but gets assimilated by the virus (highly unlikely)... etc... Then sure it is possible some new life could emerge. It won't be human though.

It would be like rolling the dice a gazillion times twice, and hoping the sequence of results would be the same.

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In 1951, a researcher took a cell sample from a cancer. These cells have mutated into a form that is independent of the human body, they live and thrive on their own. (Well, at least in laboratories)

This cell line is called HeLa from the name of the patient.

It is much used by researchers since it grows easily and is still almost genuine human cells.

If the spaceship laboratories had samples of HeLa they could very well escape after a crash. On an otherwise unpopulated planet they could survive and even thrive.

Of course, the chance of these cells evolving back into something humanoid is slim. Even if you have all the genes you would have a severe chicken/egg problem, or rather a human/womb problem.

Still, if a future researcher were to come to this planet and take samples of the local life they would be severely puzzled.

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  1. Due to wind patterns and the spaceship's weight compared to the local sand, the spaceship sinks deep under the surface and becomes unfindable without high-tech tools. That protects it from UV and looting for a few thousand million years.
  2. During the crash, moss/acarian/other tiny life forms were peppered on the planet's surface, where some started striving.
  3. Two thousand million years later, this life has evolved into intelligent creatures (the Zorglubs) who spend their days studying cloning and biotechnology.
  4. Despite their lack of interest for underground exploration, the Zorglubs finally find the buried spaceship, and quickly understand what the samples are (even in their now-fossilized state).
  5. As they always do with all fossils they find, the Zorglubs clone each DNA sample, creating a collection of humans.
  6. The Zorglubs put these humans in the planet's zoo, where they entertain young Zorglubs for generations.
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No. But a colony ship doesn't just carry DNA.

Instead it would carry a selection of biotech to terraform the planet. This is going to realistically take 1000s if not millions of years.

The ship might first sterilize the planet with something akin to nuclear weapons, then release life forms adapted for the streilized environment. Layers of later life forms would be designed to survive in the environment generated by the previous. You'd have an oxygen catasrophy, release more complex animals, complex life forms like lichens that can break down the surface and generate soils, etc.

Each epoch would be designed to thrive in the environment predicted to be generated by the previous epoch. Possibly to make the situation work more reliably, a sterilization period (nukes) would occur to "clean slate" the world and prevent adapted previous-epoch creatures from out-competing the new-epoch creatures.

Once the world is reasonably terraformed, multicellular plants and animals can be created. When a functioning macro-scale ecosystem exists then it becomes safe to add humans to the mix.


An alternative to the nuke-and-reseed approach might be to use viruses to guide evolution. You could imagine a high-tech civilization which knows of various novel "keyhole" strategies unlikely to be invented or defeated by greenfield organisms.

Use those to create viruses, and release said geneengineered viruses to cause expected existing lifeforms to evolve in certain directions.

But that seems harder.

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It's impossible to say for sure.

The manifestation of life and its evolution are quite possibly, a predominant byproduct of chaotic chance & data, to the power of billions of years. However, (from reading your comments), I think what you're looking for, is a fundamental scientific concept, known as falsifiability.


Falsifiability.

Falsifiability or refutability of a statement, hypothesis, or theory is the inherent possibility that it can be proved false.
A statement is called falsifiable if it is possible to conceive of an observation or an argument which negates the statement in question.

Falsifiability | Wikipedia, the free encyclopedia
https://en.m.wikipedia.org › wiki › Falsifi...


What does it mean for something to be falsifiable?

Falsifiability or refutability is the logical possibility that an assertion could be shown false by a particular observation or physical experiment. That something is "falsifiable" does not mean it is false; rather, it means that if the statement were false, then its falsehood could be demonstrated.

Falsifiability | Princeton University
https://www.princeton.edu › tmve › docs

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