Sometimes, the course of human evolution can lead to a sub-division. Those in the position of power become a higher caste of human beings, and those in the working class are albinos with leech-like mouths who have a taste for human flesh. The latter is due to adapting to living underground by becoming a troglofaunal species. Darwin didn't really think about this possibility, but H.G. Wells certainly did.
In The Time Machine, Wells introduced the Morlocks, hideous troll-like beings that haunt the night while the innocent Eloi culture sleeps. The book implies that it is kind of a Blue and Orange Morality: the Eloi have no conception of altruism, art, love or even the future tense. They don't actually have a culture. The Morlocks, on the other hand, are actually productive society members: they just breed the Eloi like cattle, and for the same purpose. The narrator speculates that, as the upper class constantly pushed the lower class below ground, the upper class lost the ability to think and work for itself, leaving the lower class adapted to operating heavy machinery and thinking logically. The entire thing is commonly interpreted as a critique on Victorian society, including the notion of Evolutionary Levels that later versions of the trope tacitly play straight.
This concept has since evolved into a monster archetype much like vampires and zombies but hasn't been overused like those tropes. In contemporary versions, the "Morlocks" (aka grimlocks, crawlers, hunters, hadals, etc) are usually descended from humans who became trapped underground by mischance or were driven into hiding there by their enemies. Echolocation is a common ability for such creatures, and Wells's class-conflict subtext has largely gone by the wayside in them.
Common in science fiction and fantasy, the Morlocks usually represent everything that science and art cannot redeem in the working class. This is a somewhat insidious remnant of Victorian phrenology and its ideas of Evolutionary Levels, and has left a huge impact in genre fiction.
- The Big O features the wealthy living in domes and the poor struggling to survive outside them.
- In the anime of From the New World the Bakenezumi are anthropomorphic rodent beings which live in servitude to the psychically powered humans, then it is revealed that they've been aiming to overthrow humans all along, and furthermore it's revealed that they are the mutated descendants of the percentage of humans who didn't have psychic abilities.
- The Morlocks are supporting characters, being mutants whose mutations are physically disfiguring and who live underground with others of their kind. Of course, even among the Morlocks, there are hierarchies, and the Tunnellers look down on the Drain Dwellers (and vice versa). Only two Morlocks, Marrow and Sunder, have ever been members of the X-Men proper (and Sunder was a member for only about 1 or so issues), reflecting the bad blood between the two groups.
- There's another group of mutants roaming in London's sewers that make the Morlocks look like supermodels.
- The League of Extraordinary Gentlemen : An issue of Allan and the Sundered Veil deals with Morlocks where they are revealed to be aliens.
- Legends of the Dead Earth: Subverted in Wonder Woman Annual #5. The Ratbats are a seemingly savage and barbarous race of creatures who evolved from one of the two groups of human survivors on a Generation Ship. They have been in constant conflict with the Unremembered for resources aboard the worldship for generations. AlyXa, a rebellious 18-year-old member of the Unremembered, managed to sneak into the Ratbats' territory without being seen. While there, she receives recorded memories of Wonder Woman and her exploits on Earth when in the proximity of a memory transfer device being used by a female Ratbat. When she uses it herself, AlyXa experiences residual memories drawn from the female Ratbat's mind and she discovers that the Unremembered have badly misjudged them. They are not savage, animalistic brutes but intelligent beings with a sophisticated society, which is more advanced than that of the Unremembered in some respects. For instance, female Ratbats are considered equal to the males while the women of the Unremembered are considered to be the males' property.
- Metropolis, both the anime and the 1920s silent film, have an under-caste of workers who serve the upper classes. In the silent film, the workers are almost more robotic than the robots, though still undeniably human, and the film's relatively positive ending definitely reflects this.
- The Descent has the Crawlers, pale carnivorous hominids who have adapted to living underground but have become mindless predatory animals. H.G. Wells also happens to be one of Neil Marshall's favorite writers.
- The Hunters in Pandorum are very similar to the Morlocks but their evolution was manipulated and their ancestors were trapped on a spaceship rather than underground. They even used the heads of the Morlock costumes from the 2002 adaptation.
- The creatures in C.H.U.D. are morlock-like to some degree.
- The Time Machine:
- The Morlocks in the original novel, the Trope Namers, were actually the more advanced race, providing all the food and luxuries the mentally deficient Eloi depended on, essentially farming the child-like Eloi like cattle. They were supposed to be descended from the working classes of modern-day societies, who, as class divides grew sharper, spent more and more time underground tending to industry and machinery. Over time, they evolved into a race of pallid troglodytes who kept the machines running out of instinct as much as anything, still tending to the descendants of the indolent upper classes (who they over time adapted to feed on).
- Subverted in The Time Ships by Stephen Baxter. After the time traveler accidentally changes history, advanced Morlocks live on the outside surface of a Dyson sphere, living in darkness because it allows a better view of the universe. Meanwhile the "new Eloi", basically standard humans, are busy blowing themselves to bits in pointless wars on the interior of the sphere (where they can see the sun). At the end of the book, the time traveler vows to try and view the original Morlocks as potential sapient allies and goes to try and deal with them.
- H. P. Lovecraft:
- The creatures in "The Lurking Fear" are somewhat like Morlocks as they are carnivorous de-evolved apelike humans. However, it's not social class and evolution that turned them into this, but generations of inbreeding.
- One of HPL's earliest stories, "The Beast in the Cave", tells of an encounter between a lost cave-explorer and an ape-like subterranean creature he thinks is this trope. At least, until the dying creature utters a few final sounds, revealing itself to be an ordinary man who'd been lost in the vast, pitch-black caverns so long that he'd reverted to animal-like behavior.
- The "Children of the Night" from Robert E. Howard's stories are the degenerate subterranean descendants of a primitive people driven underground by the arrival of the Picts in the British Isles. Many of Howard's period stories from Celtic times features these dwarfish, hissing mini-Morlocks as a menace, and by the 20th century they've diminished and inbred until only one remains, which looks more like a snake than a human.
- 1984 by George Orwell gives us the Proles, the underclass of apolitical nobodies who dwell in squalor and ignorance beneath the Party who run Oceania.
If there is hope, it lies in the proles.
- The Lord of the Rings:
- Orcs are sometimes identified as originally Elves who were subverted by the will of Morgoth, Sauron's master from The Silmarillion. Other times they're the result of Morgoth trying to create his own version of the children of Ilúvatar (elves and men). Tolkien went back and forth on the matter repeatedly, and hadn't settled on a definitive version even when he died, mainly due to trying to reconcile his dislike of Always Chaotic Evil with his belief in Evil as inherently incapable of creativity.
- Gollum was born a perfectly normal proto-hobbit, but centuries of living under the Misty Mountains under the corrupting influence of the One Ring gradually turned him into a degenerate nocturnal creeper.
- Jeff Long's The Descent and Deeper, with their pale cave-dwelling cannibal hadals who have evolved to adapted to their conditions, owe a lot to this trope.
- The Night Land and Awake in the Night Land have the Abhumans, which are prophesied to eventually replace the regular humans.
- Not subterranean, but the Ab-locks of Secrets of the Fire Sea owe their name to this trope. They are aggressive, feral pack-dwelling hominids descended from an ancient Jagonese civilization that destroyed itself which are bitter enemies of the much larger, more solitary ursks which are also The Morlocks, but derived from Ursine Aliens from the same long-ago civilization, rather than humans.
- Doctor Who has occasionally portrayed the future of humanity this way. "Utopia," set at nearly the end of the universe, has ordinary humans plagued by the "futurekind," tattooed cannibals (or maybe technically not) with sharpened teeth, who seem barely capable of speech.
- In the Star Trek: The Original Series episode "The Cloud Minders", the world of Ardana seems to be headed this way. The Troglodites are still recognizably the same species as the inhabitants of Stratos, but constant exposure to Zenite gas is gradually destroying their higher mental functions.
- Blake's 7. The artificial planet Terminal is created to study the future evolution of Mankind. Turns out it's a vicious ape-like creature. In an inversion of this trope, the scientists who study them live in an underground base, while the Links roam the surface.
- Star Trek: The Original Series. The much-maligned episode "Spock's Brain" also inverts the Trope Namer. The Eymorg, a Lady Land of beautiful but childlike women who live in an automated Underground City, abduct the Morg — the male Future Primitives who live on the desolate surface of the planet (though it appears they use them for servants and procreation rather than food). The women aren't simple because they're women, but because thousands of years in a physical Lotus-Eater Machine has atrophied their intelligence; otherwise it takes Men Are Strong, Women Are Pretty to an extreme.
- In merchandise, the villains of Power Rangers Mystic Force are explicitly called Morlocks. However, despite them being humanoid evil creatures living underground, these Morlocks have no further similarity to this trope, as they are a collection of supernatural beings based on creatures from mythology or fantasy. In the show itself, they aren't even referred to as Morlocks, but rather "The Forces of Darkness".
- The Gifted, being set in the Marvel-verse, prominently features the Morlocks in the second season.
- Journey into Space: Subverted in The Return from Mars. The Talians tell Jet, Lemmy, Doc and Mitch that the Sotteers are primitive and aggressive genetic rejects who detract from their perfection. While the Sotteers lack the Talians' so-called physical perfection, it turns out that they are every bit as intelligent and civilised as the Talians.
- Dungeons & Dragons:
- In the supplement Races of Destiny, there are the Sharakim, who look like orcs and are seen as sub-human because of it, but are a subversion. They actually are "tainted" humans and are generally Lawful Good, while having a thriving arts and culture to show their difference from normal orcs.
- Grimlocks, originally from the 1E Fiend Folio, are a more straightforward version of this trope, though it's not entirely clear if they were originally human (it's usually a Depending on the Writer thing). They have stone-gray skin, sharp teeth, and no eyes whatsoever; they rely on Super Senses of touch, smell, and hearing to get around in the darkness. Their cannibalistic tendencies and lack of sight make them popular servants with medusas (who like having minions that can't get turned to stone by their gaze) and mind flayers (who only eat the brains of their victims and leave the rest to the grimlocks).
- The Cynidiceans, from Basic D&D module "The Lost City", could be considered the precursors to this trope: formerly surface-dwelling humans who have adapted to life underground by developing infravision and the loss of pigmentation, but haven't (yet) degenerated so far as to turn cannibal. They do spend most of their lives drugged out of their minds on fungal narcotics and are dominated by the cult of an Eldritch Abomination that's urging on their decline, so barring intervention from outside, they'll probably sink that low eventually.
- In the Forgotten Realms, the race of skulks arose in much the same fashion as Morlocks, being descended from humans who escaped slavery at the hands of various evil Underdark creatures but couldn't find their way back to the surface. An enigmatic Neutral deity of caverns and darkness taught them a spell granting superior stealth and senses, the better to endure their incredibly-hostile new environment, but overuse turned its recipients permanently into skulks.
- Vampire: The Requiem has a Nosferatu bloodline named the Baddacelli, nicknamed "The Morlocks". They are blind and live in the sewers.
- In Vampire: The Masquerade, these were the Nosferatu. While Requiem makes the Nosferatu creep more subtle, Masquerade made it a lot more obvious, making them all deformed in some highly visible. As a result, most of them lived in "warrens" under the city.
- Pathfinder features morlocks, using the name from The Time Machine, as degenerate, cannibalistic and demon-worshipping underground-dwelling creatures that were once human. In a subversion, though, they were actually descended from the upper class of an ancient empire who fled deep underground, only to devolve into flesh-eating subhumans due to millennia of inbreeding and exposure to magical radiation. Early Pathfinder sourcebooks also mention D&D's grimlocks, but due to the two races being almost identical, they've quietly dropped the grimlocks.
- Atomic Highway has morlocks as a title for degenerate, subterranean radiation mutants, serving as an Evil Counterpart to the playable "Trogs" (humans who, after the apocalypse, settled in caves and subway systems).
- Deep below the Martian city of Y'therthl in Rocket Age is a network of tunnels full of the mutants occasionally created by the ritual use of genetic engineering technology. Generally hideous and broken parodies of those above, they can still run the whole gamut of morality.
- The thematic play Brand by Henrik Ibsen has a vision how of regular humans will evolve. It starts out with an idea of "eartbound thralls", gradually devolving into something similar to Morlocks (Brand actually uses the term Dwarfs, but the description fits), all in the mind of the titular character, who has a really grim view of where history is leading mankind.
- In The Elder Scrolls, the Falmer of Skyrim are an almost perfect example of Morlocks. Thousands of years ago, they were a race of Mer (Elves) with a territory covering Skyrim and Solstheim, and who had a civilization that rivaled even the Altmer (High Elves). However, they would clash with the ancestors of the Nords who were coming over to Skyrim in droves from the freezing-over continent of Atmora. Ysgramor, an Atmoran leader, would rally 500 of Atmora's greatest warriors and lead them on a crusade to exterminate the Falmer. He almost succeeded, driving the survivors to beg for help from their Dwemer cousins. The Dwemer agreed to take them in, but forced them to eat toxic fungi that rendered them blind and decayed their minds, and which their physiology became dependent upon to survive. The Dwemer used them as slave labor and test subjects in their experiments. (For this reason, Knight-Paladin Gelebor, the last uncorrupted Snow Elf, refers to them as "The Betrayed.") Later, the Dwemer did something which caused their entire race to vanish from any known plane of existence in a single instance, leaving their Falmer slaves without masters in their underground advanced cities throughout Skyrim. Ever since, the Falmer dwelt in these underground places. If they run across any surface dwellers (either people venturing into their lairs or one of their rare excursions aboveground) they will kill or capture and enslave them. They also are known to torture their captives, and feed them to their pet Chaurus, judging by the number of human remains in Chaurus pens. If Alftand is anything to go by, they also skin surface dwellers and make leather from them. About the only Morlock trait they don't have confirmed is eating the surface dwellers...but sometimes, when you kill one, you find 'Human Flesh' in its inventory... and human remains in their refuse heaps... Perhaps the most disturbing sign of their degradation is the fact that their souls can be captured in white soul gems. A black soul gem is needed to capture the soul of a sentient being, while white soul gems can capture the (lesser) souls of beasts. The Falmer have fallen so far that their very souls have been affected. (And given the Dwemer's status as masterful enchanters, this was very likely intended as part of their corruption of the Falmer. It would basically give the Dwemer an ample source of batteries.)
- Parodied in Barkley, Shut Up and Jam: Gaiden with the furries of Cesspool X. They're not actually mutants, simply people who have undergone Magic Plastic Surgery to look like the creatures of their fantasy. Unlike most examples, they're not Always Chaotic Evil despite being the subject of derision for the "norms" (including Barkley) and are portrayed as people who simply want to live out their relatively harmless fantasies.
- In SteamWorld Dig, all of humanity has degenerated into this. They're known as Shiners by the Steambots and treated as savages, and they don't do much to disprove that fact. A more intelligent, friendly Shiner colony does show up in the sequel, but they turn out to be the real villains of the story.
- In Grim Dawn Trogs are pale-skinned humanoids inhabiting the deepest caves. They're considered to be Beastkin rather than humans, suggesting that they're an offshoot of trolls or grobles. While they're not explicitly man-eaters they make heavy use of Blood Magic and bone weapons and shields.
- Futurama: Spoofed through the Dumblocks is the episode "The Late Philip J. Fry". The gang is on a forward-only time machine looking for a backwards time machine, and comes to the year 5,000,000, when humanity has split into two races: a foot-tall, bright pink and highly advanced species and the Dumblocks, stupid, vicious brutes, who live underground. The Eloi-like race says they could have a backward-going time machine ready in five years. The gang returns five years later to find that the Dumblocks have taken over and killed all the other humanoids.
- In one episode of the Superfriends, "The Conquerors of the Future" they meet expys of Morlocks, called Barlocks. They are otherwise identical and trying to break in and attack the domed cities of the normal-looking people of the year 3000.
- In New York City there are many Urban Legends of "Mole People" living Beneath the Earth in abandoned tunnels. These legends have some basis in fact, due to the many railroad tunnels under Midtown Manhattan (not the New York City Subway, however) which were poorly patrolled prior to the Turn of the Millennium. This allowed a variety of eccentrics to dwell there, some of whom never left.
- While it's never been documented in mammals, the adaptation of invertebrates, fishes, and salamanders to life in caves is well known. Pigmentation is lost due to the metabolic expense of producing it in a nutrient-starved, lightless habitat where color doesn't matter, and eyes often degenerate or disappear because they're even more costly to grow and provide a potential avenue for infection.