"Speculative biology" (also referred to as "speculative zoology", though it is by no means limited to animals) refers to when people speculate how a species could evolve under certain circumstances.
The most common situation used for the animals to evolve is After the End: "What would the world be like once humans go extinct?" Another common situation is "What animal(s) could become as advanced as humans and how would they?" Other works focus on the question of "What if humans never evolved?", feature aliens on different types of planets, or just end up creating animals that could exist. Often, the aim of Evilutionary Biologist is to see how humans/certain animals would end up if he hastens their "evolution".
Speculative biology is very popular online amongst wannabe biologists and animal fans, especially on sites like Deviantart, and Sturgeon's Law applies here. This sort of work is common in fandoms that feature fantastical animals such as Pokémon or My Little Pony: Friendship Is Magic; artists will invoke Reality Ensues and try to revamp the characters in a way that makes more biological sense. However, it's also a topic that gets professionally discussed. Several books and a few documentaries have also been created on the topic of speculative biology.
Despite the name, speculative biology is often not very scientifically accurate. Many artists end up coming up with inaccurate animals and circumstances that most likely couldn't occur. Every so often however, years later a species is discovered that resembles a previously fictional animal.
- Realistic Pokémon is a series of fanarts depicting interpretations of Pokémon as if they were, or had evolved from, real-life animals. Some, like Zapdos and the Eeveelutions, remain largely what they are in canon, albeit with more realistic anatomy. Others get more drastic redesigns — Giratina is interpreted as a giant insect native to extremely deep caverns (the Distortion World) where the air pressure is high enough for its larval form (Giratina's Origin Forme) to "swim" through the air. Likewise, Voltorbs are drawn as red-and-white armadillos that "explode" by violently uncoiling.
- Tiny Sapient Ungulates is a realistic take on My Little Pony: Friendship Is Magic:
- The ponies themselves are a species of basal ungulates with short muzzles and big ears, as well as legs still ending in five digits tipped with hoof-like nails and with some limited mobility (explaining their in-show ability to hold objects with their hooves). Pegasus wings are reimagined as lobed wings of skin supported by elongated fingers like a bat's.
- Griffons become hexapodal birds that evolved from solitary predators. As such, they only typically interact for territorial posturing or trade and are mentally predisposed to see all forms of interaction as one of these two, explaining their aggressive and greedy behaviors.
- Changelings become enormous four-legged insects who evolved to mimic ponies (their food source) and that feed on both emotional energy and solid matter. Their transformation in "To Where and Back Again" is interpreted as Chrysalis essentially starving her hive by denying it both physical food (as she wrongly believed they didn't need it) and the social interaction they need for optimal feeding, only allowing them to grow into stunted neotenic forms. Thorax's takeover allowed them to start feeding properly again and morph into their true adult shapes.
- This Very Wiki has a Just for Fun series, The Pokédex - Extended Fanon Edition, that takes the premise of Pokémon Up to 11 and documents the creatures as if writing a scientific article about real-world animals, dealing their biology, behavior, reproductive habits, diet and depiction in human culture.
- Deviantartist Chritopher Stoll,mainly with his two series, A Natural History of the Fantastic (which cover mythical creatures), and PokeNatomy (which covers Pokemon).
- Dougal Dixon is probably the Trope Maker of this genre.
- After Man is a 1981 book on how Earth could evolve in the 50 million years after humans go extinct. It is one of the most famous and influential examples.
- The New Dinosaurs: An Alternative Evolution is a 1988 book about how dinosaurs could have evolved over 68 million years if the mass extinction had not happened. Due to being made in the 1980s, the book is very outdated in many respects.
- Man After Man: An Anthropology of the Future is a 1990 speculative fiction book that focuses on individual characters rather than whole species. It starts After the End in the 22nd century, when the Earth has been ruined by human overpopulation and destruction of the environment and the humans decide to launch spaceships to find other livable planets. Scientists created two humanoid species — the frog-like "aquamorph", and the "vaccuumorph" that only can survive in the airless voids of space — in order to help build the ships, as well as a species of gilled manatee-like humans.
Over five million years the Earth recovers, and the descendants of the humans who stayed behind genetically engineer a variety of apes from human stock to replace the by then long-extinct megafauna — yeti-like tundra dwellers, Australopithecus-like dwellers of temperate forests, long-legged grazers to replace antelope and buffalo, and apelike arboreal inhabitants of tropical forests. Over millions and millions of years, these speciate into even more forms — the temperate forest-dwellers, for instance, give rise to spindly, sharp-toothed parasites of bigger humans, a people with Genetic Memory, sloth-like colossi and saber-toothed hunters, while the grazers evolve into desert-dwellers who inhabit insect-like hives. The manatee people stick around for most of this
This goes on until one day the descendent of the space-faring humans come back, colonize the planet, engineer the human animals into various forms of Organic Technology and wreck the Earth even worse than before. On the whole, the book is heavy on Body Horror and the unsustainability of technological civilization, and uses a lot of Artistic License – Biology.
- The literary mockumentary The Snouters: Form and Life of the Rhinogrades, by the German zoologist Gerolf Steiner in 1957, may be one of the earliest semi-serious examples, as the book documents the bizarre endemic inhabitants of a fictional island chain, cartoonish shrew-like creatures that have evolved to do every conceivable activity with their noses (walking, eating, jumping, swimming, reproducing etc.). Despite the absurdity of the subject, the snouters are treated with absolute seriousness and strict scientific rigour.
- The 2013 book Cryptozoologicon tries to reinterpret cryptids as plausible animals.
- One of the plot elements in The Mote in God's Eye was how the various subspecies of Moties evolved. Determining how this occurred was crucial in determining that some of the Motie bodies ejected from the Crazy Eddie Probe were Warriors, which exposed one of the Moties' darkest secrets.
- King Kong (2005) got a companion book called The World of Kong: A Natural History of Skull Island, where the biology of the various monsters seen in the movie, from the dinosaurs through the giant bugs to Kong himself, got described in a semi-scientific way.
- In the Animorphs prequel novel The Ellimist Chronicles, the Ketrans play a game that revolves around slightly modifying the conditions of their chosen virtual creatures' planet in order to influence their evolution towards a specific direction. Different players' creatures can even come into contact with one another through space travel.
- A common pattern in Larry Niven's Known Space novels is Niven Playing With this trope. The Ringworld sub-series in particular explores the many potential hominids that Homo habilis might have diversified into, given unlimited space, no predators, and a variety of vacant ecological niches to occupy.
- The Long Earth series explores parallel Earths, including ones where hominids developed along different lines or where other animal lineages developed intelligence instead.
- The Future Is Wild is a 2002 Animal Planet documentary. It is a Spiritual Successor to the speculative evolution book After Man. In contrast to the book, the documentary says that humans simply left to live on another planet rather than went extinct. The documentary has been criticised for containing animals that are implausible, such as a giant land squid millions of years into a future where mammals have died out and other species fulfil their niches.
- Dragons: A Fantasy Made Real is a 2004 mockumentary where the remains of dragons are discovered in a cave. It goes onto describe how different dragon types could have evolved, how they would have worked, and why they went extinct.
- Mermaids: The Body Found is a 2012 mockumentary and is the Spiritual Successor to Dragons: A Fantasy Made Real. It describes how a species of ape could have evolved into an aquatic animal, eventually becoming mermaids. Unlike its predecessor it is a Found Footage Film. It's most famous, though, for being mistaken for an actual documentary when it aired, since the disclaimer that it was a work of fiction was hard to see.
- One episode of Cosmos had Carl Sagan discussing a theoretical ecosystem on Jupiter in which the animals had evolved into Living Gasbags in order cope with the planet's conditions.
- The Doctor Who episode "The Lazarus Experiment" has Richard Lazarus being mutated into a fearsome giant centipede/scorpion-like monster after an experiment with an anti-ageing machine goes wrong. The Doctor describes the monster as a creature of evolutionary potential - something that evolution could have turned humanity into if it hadn't gone the "two arms and legs, ten fingers and toes" route - lying dormant within Lazarus' genes.
- One episode of the documentary series Through the Wormhole was about how aliens could realistically look like depending on the planet they are from.
- Dinosapien asks the question "What if non-avian dinosaurs hadn't gone extinct?" and goes with it. In it, an earthquake opens up and reveals a Lost World where dinosaurs survived the mass extinction and evolved further.
- Traveller: When the game was first created, a key part of the design of its alien races was deciding not just how they evolved, but how they developed intelligence.
- The central idea of Spore was creating alien species, making them adapt to the environment and evolve into sentient beings. However, it changed direction mid-production, leading to more cartoonish and unrealistic gameplay and art style. Multiple attempts were made since then to make a game that would be closer to Spore's original concept.
- The Pokémon franchise occasionally dabbles in this, what with the way some PokeDex entries detail the creatures' biology. The Alola games specifically go into detail on the hunting habits of Pokémon. However, they're just as likely to go for Rule of Cool, and most of the "science" they contain is pure nonsense.
- Scanning enemies and other alien lifeforms in Metroid Prime 2: Echoes gives biological and behavioral details on them.
- The Wiki Rule even applies here. Speculative Evolution Wiki lists works about speculative biology, amongst other things.
- The Youtuber TREY The Explainer usually focuses on actual paleontology; however, he has dabbled with this:
- He once did a video on what he thinks aliens would actually look like. He is very much against the prevalence of Humanoid Aliens and The Greys in media.
- In his videos on debunking cryptids, he discusses near the end what he believes they hypothetically would realistically be. For example, in his video on the Loch Ness Monster he speculated that it wouldn't be a plesiosaur but instead would be a giant leech.
- Likewise, his video on the Flatwoods Monster ends with the theory that it would be a giant salamander, rather than an alien.
- The Speculative Dinosaur Project is a modern-day Spiritual Successor to the 1980s book The New Dinosaurs: An Alternative Evolution. It's a speculative biology project on how dinosaurs could have evolved if the K/PG mass extinction had not occured.
- Sagan 4 was a web project about creating an entire alien ecosystem that evolved from a single unicellular life form, inspired by discussions of the game Spore which was then in production.