That's right, kids: Pasteur Was Wrong.
Funny thing, science. For ages, there was no certain way of determining that maggots grew from eggs laid by flies, so it was generally assumed they arose naturally from putrefying meat and other sources. It was a different time then — heavier rocks fell faster; bloodletting cured illness, etc.
Funny aside: Spontaneous Generation is an ancient example of Artistic License – Biology and Pregnancy Does Not Work That Way. It makes it possible for living things to spring up from non-living — or at least non-fecund — things through a vague and inexplicable process. It's most noticeable in myths — creation myths generally have no choice but to resort to this explanation for the First Mover that comes into existence after chaos. However, some scientists continued to believe in spontaneous generation of small creatures (e.g., flies appearing on carrion) up until the 18th century or so, when experiments with sterile, vacuum-sealed containers disproved it for good.
It should be noted that abiogenesis, the extremely simple chemical processes scientists propose as the origins of life, is NOT the same as spontaneous generation, the emergence of complex organisms from non-living matter, such as maggots forming from rotting flesh or truffles from small rocks.
See also Born of Magic and Love Imbues Life. Sometimes, It Came from the Fridge.
Real Life and Mythology
- The Greek philosopher Aristotle, and by extension his following, believed that insects had no parents, but were born right out of mud, corpses, etc. This was in part related to the concept of life and breath being related note : as insects didn't appear to breathe like mammals or birds, they weren't alive in the same sense that mammals and birds were.
- Given the way mushrooms seem to pop up overnight and their mysterious, invisible reproductive process (spores, which are so tiny they cannot be seen without a microscope), it's easy to see why people used to think mushrooms generated spontaneously and circles of fungi were magical "fairy rings."
- The Boltzmann Brain. According to the theory, it should be possible for a human brain, complete with a set of Fake Memories, to simply appear from random chance, and given enough time, though it likely would be absurdly long period of time, it definitely should happen. Statistically, this could mean that you are actually more likely to be a Boltzmann Brain than a real human. Physicists try to resolve this by avoiding models of the universe where Boltzmann Brains are likely.
- The Wooing of Étaín: Etain is reduced to a puddle of water by a jealous rival. As it is heated by the sun, eventually a maggot is born from the puddle, which moults into a beautiful fly.
- Gaia, the goddess and personification of the earth, just sort of... forms from the dark, shapeless nothing that was primordial Chaos. Alongside her sprang forth Tartarus (the deepest abyss and also the closest approximation to Hell Greek Mythology has), Eros/Phanes (the god of love), Erebos (darkness personified) and Nyx (embodiment of night).
- Aphrodite, among others, sprung into existence when sky-god Uranus's newly liberated ballsack hit sea foam. Ouch. Some of his blood also fell on the earth, i.e. his wife/mother Gaia, from which sprouted the Giants, ash-nymphs, and Furies.
- Gaia is very prone to this in general. She has the uncanny ability to just create offspring out of nowhere, for example the giant scorpion that killed the hunter Orion.
- Deucalion and his wife repopulate the human race after The Great Flood by tossing rocks over their shoulders, causing whole intelligent human beings to spring up.
- As Perseus flew over the desert on his winged sandals, blood from Medusa's severed head fell on the sand and formed "poisonous asps and adders," as a "Just So" Story element. Pegasus and his less popular, human or winged boar brother Chrysaor were born from Medusa post-mortem, and depending on the version, are either her children by Poseidon or an example of spontaneous generation. In one, her blood falls in the sea and spawns them, Aphrodite-style.
- The teeth of Ares's water-dragon that Cadmus killed, once sown in the ground, grow into sentient warriors. In Cadmus's story, five of them help to found Thebes and produce offspring. In Jason's far more famous adventure, the remaining teeth's newborn warriors are all killed.
- Older Than Dirt: all Ancient Egyptian creation myths start with spontaneous generation.
- In one creation myth, one version has Hathor, a bovine sky goddess, created from a cosmic imbalance of primal forces. Then the sun god Re hatches from an egg laid on top of Hathor by a big heron (itself a sun-god) from, um, somewhere.
- Alternatively, Re arises, weeping, out of a lotus bloom whose bud was formed from said prior imbalance, rather than Hathor. Or else the bud grew out of the waters of primordial chaos.
- Another myth has the universe being masturbated and/or spat out by Atum, starting with the gods Tefnut and Shu. Atum created himself from nowhere first.
- In the Ogdoad myth, the first eight gods of air/invisibility, darkness, eternal time, and water/chaos grew from the first mound of earth that spontaneously rose from the primordial chaos. The mound itself was deified as a god, and depending on interpretation Nun, god of the primordial chaos, could be his own father or grandfather.
- In Norse Mythology, life began when the warm air of Muspelheim hit the cold ice of Niflheim, creating the giant Ymir and the cow Audhumla. Other giants grew from Ymir's sweat and Bori, the first of the gods, appeared from Audhumla's salt lick. Fun times.
- Natural Histories: The narration speculates that the reason for why fish are present in the lake formed from a large quarry, despite it having no inlets or outlets that fish could have used to reach it and having been filled only by rainwater, is that they spontaneously appeared within it; it's mentioned that sometimes mice will just appear in stacks of hay, or maggots in meat, and that something similar may have happened here. A more mundane explanation that the narration proposes next is that fish eggs were just carried in on the feet of birds.
- Clash of the Titans (1981): In this adaptation of the myth of Perseus, it's giant scorpions that sprout from drops of Medusa's blood.
- TRON: Legacy: The Isos spontaneously generated themselves from the Sea of Simulation and became an unknown, uncontrollable factor on the Grid. Flynn was thrilled, but his administrator / counterpart Clu viewed them as a threat, setting into motion the events of the film.
- Autumn: The survivors seem to be under the impression that decomposing human bodies spontaneously generate all manner of disease.
- Earth's Children: No one except Ayla believes conception involves men having sex with women. Rather, in their view the Great Mother (for the Others) or totem spirits (among the Clan) are said to do this. However, at least the Others acknowledge children's looks can have an influence by men's spirits, though it still isn't something physical for them. Ayla manages to convince people over time however, pointing out how children usually resemble their mother's mates, virgins don't have them etc. It's hinted this is going to usher in a social revolution afterward, as men become more possessive over women as a result to make sure their mates' children are theirs genetically.
- In Hayy ibn Yaqzan, this is given as a possible explanation for how Hayy came to be a Wild Child on a Deserted Island. The intense heat of the sun combined with a particular mixture of elements in a certain spot under the ground and spirit infused by God to create life. Hayy gestates until the mud around him dries and cracks, revealing a fully-formed infant.
- Journey to the West: Sun Wukong hatched full-grown from a giant stone egg. Not much detail is given as to how or why this happens.
- The Kingkiller Chronicle: The Adem believe that babies just sort of happen and are completely unable to accept the idea that men have anything to do with their creation, to the point of openly mocking and rejecting Kvothe's assertion to the contrary.
- Paradise Lost: Satan claims that he arose spontaneously, out of "pregnant possibility", i.e. the idea of him was so fundamentally awesome that he couldn't not exist. This is his justification for disobeying God and rejecting him as a creator.
- "The Red Tower": The narrator believes the Tower originated as a crude sketch in the desolate surrounding landscape, that slowly solidified and reddened like a sore, and attributes the Tower with qualities like ambition and perverse defiance as though it formed intentionally.
- Thud!: According to the dwarfs' creation myth, the god Tak's first action was to write himself into existence. Further, the first troll sprung unbidden from the stone egg that Tak used to make the first man and dwarf. In the traditional, conservative version of the myth, the troll went unregarded and so wanders through the world without purpose; in an alternate version, however, Tak was pleased with the stone's tenacity and gave the troll His blessing.
- Babylon 5: Lorien claims that his entire super-advanced species was created spontaneously by the universe.
- Diablo: It's said that demons arise spontaneously in the footsteps of the Prime Evils. This is borne out considering how demon-infested places that they've been are.
- Ōkami: According to his backstory, sub-boss Red Helm spontaneously sprung from the spilled blood of Orochi, a bigger bad.
- The Sims: All the Sims have to do in order to make a baby (before expansion packs and later editions with the "Woo Hoo" function came out) is kiss passionately, and suddenly a baby bassinet arrives in a shower of daisies.
- Star Wars: The Old Republic: During Knights of the Eternal Throne, the PC visits the Sith Emperor's home planet Nathema, where thousands of years ago he enacted a Sith sorcery ritual that consumed the life and Force essence from every living thing on the planet. When you revisit the planet in the "Nathema Conspiracy" flashpoint after destroying the Emperor, the Force has come back and the previously barren, dusty wasteland is starting to green up again despite the fact the planet was literally lifeless before, barring whatever its few offworld visitors might have imported.
- Object Invasion: Sometime after all life on Earth went extinct, objects spontaneously evolved to be living beings.
- Goodbye Strangers centers around strange creatures called strangers that seem to manifest spontaneously when conditions are right. There are many different kinds of strangers that all have different conditions for appearing. They exclusively appear in areas that are populated by humans and all except one of them, which is always the first kind to appear, require the presence of at least one other kind of stranger to manifest so once an infestation of them has started they will appear in somewhat predictable patterns.