A science-fiction trope, most common in Literature wherein it's discussed that different races have essentially vanished, and everyone is pretty much within a limited range of color, usually a medium tan so to speak. Contrast with Humans Are White, which is basically the opposite idea, as well as the related Society Marches On.
Essentially, as racism fades and travel becomes easier and easier, more and more multiracial children are born until the entire world's population shares one big gene pool. It's also common for people to have a Multiethnic Name as well.
Tends to imply something of a Utopia—given how much blood has been shed over race, a world where there has been much interracial coupling is likely to have solved at least that problem. Additionally, humans in this scenario tend to have formed The Federation or there is a lot of globalization (but framed in a positive way), as this type of future naturally implies a lot of interaction between different peoples.
One particular version that's popular in anime won't have all races merge, but rather a prominent number of half-European, half-Asian people. This may relate to Japan Takes Over the World. This particular version is also popular with cyberpunk, especially the part-Japanese version.
Needless to say, this entire trope is the worst fear of ethnic supremacists/nationalists. In another way it's their dream come true. Only one race. When this doesn't happen in the future, often writers will address it via explaining that cultures or nations have settled their own planets, thus allowing them to maintain common day ethnicity in the far-flung future.
In actuality, this trope is unlikely to come to pass in the way we think of race; while closely-knit populations will often share traits for both genetic and cultural reasons, the color of one's skin is affected by multiple genes (and environment) allowing for a range of shades and complexions. See the Pashtun or Brazillians for the actual result, which is wildly varied looks often within the same family. However, over a long enough time scale the trope can happen. Though unlikely, and without selection an impossible assumption, since there are already far too many people for the population to reliably interbreed quickly and evenly enough to homogenize the existing races before new races begin to pop up without a concerted effort on the part of the entire human species.
Another unfortunate problem with the Utopian ideal this implies is that race does not always mean 'skin colour' or 'face shape' - for instance, in South Africa, people who would be considered 'just black' in Western cultures, can be/have been split into the 'Black' and 'Brown' races, even though there is no physical way of differentiating between these two populations. The historical definition of "race" in some cases also meant more like what now is termed "ethnicity". For instance, the English "race" etc. that would look not very different from its neighbors. Language and culture however can be equally divisive.
- Mobile Suit Gundam had this in droves, especially the Universal Century timeline. The Zabi family was a mixed bag with all of the family members seemingly a different skin tone. Although the Zeons are frequently compared to Nazis, they are as multiethnic as the Earth Federation. The strangeness of Yoshiyuki Tomino character names adds to the ambiguity of character ethnicities.
- ∀ Gundam, set even further into the future has a good deal of tanned and generally mixed-race people inhabiting North America alongside whites and blacks. This being the result of generations of interbreeding following the Moonlight Butterfly apocalypse.
- The world of Attack on Titan seems to be leaning this way, but with much bleaker implications than usual. Instead mixing through many generations, several races are implied or outright stated to have gone extinct. Mikasa in particular is probably the last Asian person on Earth ( or so she thought), which nearly made her very valuable to the human traffickers that planned on selling her into slavery in her childhood.
- In The Savage Dragon, Kid Avenger comes from a future where everyone is Ambiguously Brown.
- In Captain America Corps., the reader is introduced to Commander A, AKA Kiyoshi Morales, the Captain America of the future. He's of mixed African American, Japanese, Hispanic and Native American descent, and owes some ancestry to Luke Cage.
- Hinted at in The Matrix films; while the humans in the Matrix itself are shown to be more or less split along the traditional ethnic lines, the humans in Zion are frequently of mixed race. Makes sense; people in the Matrix would have a much larger pool of same-race partners than the few freed humans in Zion would.
- Alluded to in Planet of the Apes. The apes stuff and display Dodge because they'd never seen a human with dark skin like him. The future humans who we see all look Ambiguously Brown.
- In Bulworth, when Senator Bulworth is on TV in brutal-honesty mode, he suggests that the US should engage in "a voluntary, free-spirited, open-ended program of procreative racial deconstruction". Seeing the blank look on the interviewer's face, he re-phrases it more bluntly: "Everybody just gotta keep fuckin' everybody 'til they're all the same color".
- Blind Uncle Rob in The Learning Tree wasn't born blind, but was blinded in an explosion. After his nephew Newt asks him if he remembers colors, Uncle Rob says yes, and talks about the colors he can see dancing in his head. Then he grows philosophical and wonders if people will get along better in the future, when their colors mix together.
- In File Under Miscellaneous, anyone who doesn't fit the (white) norm gets surgery to fit in.
- The Clone Republic. Most people are of mixed ethnicity, though most of the main characters don't follow this trope. For example, Freeman is described as "coffee without a hint of cream." Also, Japan's descendants have separated from the main empire, and they are said to be unique in their isolationism. The clones are also designed to be white.
- In The Polity series, the protagonist, super-spy Ian Cormac, is described as having the golden-brown skin tone which dominates in the Polity. The Polity isn't quite a Utopia though, more like The Federation as a benevolent dictatorship. Even then the other characters in the series come in a rather wide variety of colors.
- Ursula K. Le Guin:
- Possibly intended with dark-skinned ambassador Genly Ai in The Left Hand of Darkness. Possibly, in that while Le Guin later placed the novel within a universe where humanoid aliens colonized a number of planets including Earth, it fits the general idea of "future with The Federation and many dark-skinned people".
- Also subverted by the author in The Lathe of Heaven where an attempt to create this results in a drastic assimilation event after which everyone has grayish skin.
- Implied to be the case in The Dispossessed by a Terran ambassador.
- In one time travel story by Philip K. Dick, the future was populated entirely by brown people. Part of this is due to the fact that they reproduce through a soft form of cloning, part of it is due to inferior members of families being pressured to kill themselves, and part of this is due to race wars.
- In Ira Levin's This Perfect Day, the "Family" is genetically engineered for perfection—which in this world is an almost stereotypically Asian appearance.
- The '70s B-Grade sci-fi series, Space Ways, which is set in the far future, has almost all humans with tan to dark skin and brown eyes where natural features like red hair or blonde and blue eyes only exist as rare genetic throwbacks.
- In The Forever War, the hero leaves Earth to fight in an interstellar war using a starship drive that causes time dilation. When he returns to Earth it's thousands of years after he left, and everyone on Earth is a nice even tan, with dark hair and eyes. Oh, and they're all gay. Later taken to its logical extreme, with the entire human race becoming all clones that look completely identical, who also are part of a hive mind.
- Larry Niven's Known Space continuity has this happen.
- Partly because improvements in cosmetics make it cheap and easy to change your skin color (and features) to more or less whatever you like, so you can appear to be a member of any race you want — or like a member of no known actual race. Louis Wu in Ringworld is sporting a chrome-yellow dye job at the start of the book and is described as looking like a comic-book version of Fu Manchu, but without makeup, he looks like a typical Flatlander: "His features were neither Caucasian nor Mongoloid nor Negroid, though there were traces of all three: a uniform blend which must have required centuries."
- In the Uplift series, humanity was gradually moving toward this.
- The second Mass Effect novel has a human character looking at the quarians and thinking about how not only quarians but also the various other species tend to look homogeneous. She knows that part of that has to be just that she's unused to those other species and can't pick up on the differences, but even so there aren't serious variations in body size or coloration or anything. Then she realizes that, well, these other species have each become one race, and it's happening to humans too; humans who are purely of any one race are extremely rare. This is also mentioned in the first novel about Anderson, who has half-a-dozen ethnical groups as his ancestors, including Caucasian, Indian, African, and East Asian.
- John Carter of Mars:
- In the series, John Carter says at least twice that he expects this to happen. Considering when the books were written, Edgar Rice Burroughs must have freaked people out with that one.
- The "Red Martians" are a genetic admixture of the progenitor races. There are still White Martians in some places, along with Black Martians and Yellow Martians, but they're mostly confined to certain specific areographic regions. There are also Green Martians, but they're probably a different species. Probably. "Species" seems to have been a concept Burroughs wasn't familiar with, given that the human Carter mates with and has children by the oviparous, albeit with distinctive mammalian characteristics, Dejah Thoris, who is a Red Martian.
- Race Against Time by Piers Anthony starts out in a 20th-century setting, but later shows the 24th century, where everyone is a muddled brown color and genetic throwbacks with distinct racial features are kept in cultural preserves with a zooish quality to them. The protagonist is one such throwback, living in preserve modeled on the 20th century; he starts out believing that he really lives in the 20th century, and learns the truth over the course of the novel.
- Part of the background in the Council Wars series, by John Ringo. The sheer homogenity of humanity by the 40th century led to Change (a medical procedure, similar in use to modern-day plastic surgery. But involving the changing of your genetic code, with nanites) which allows people to turn themselves into mermaids. Or unicorns. Or anything else they can imagine. This eventually leads to the Council Wars proper.
- A variant occurs in the Antares novels. Apparently, most settled planets are homogenous - either they all came from one region on Earth, or they blended after a while. The only planet that is not homogenous is Earth itself. That said, different planets will have different dominant racial types. Altans and Sandarians are white, because their ancestors were mostly European, but other worlds have different ancestries. There is almost certainly one planet that is all black.
- Doctor Who Expanded Universe:
- Implied in The Year of Intelligent Tigers, which takes place on a future Earth colony called Hitchemus (which borders on Mary Suetopia, except for the disgruntled tigers) where almost everybody appears to be mixed race. The main One-Shot Character has a European first name, an Iranian surname, implicitly dark skin, and grey eyes. However, there are two characters described as "Black", and pale-skinned people are "exotic" but aren't considered particularly strange.
- Alluded to in an early description of 30th century companion Chris Cwej, from the Doctor Who New Adventures novels, which says that he is, by 20th century standards "the superman" ... and that this was the result of the exact opposite of how certain 20th century politicians thought it could be achieved. On the other hand, he certainly looks white, and his police partner is not only black but comes from a family very proud of their pure African heritage. But it appears that society is on its way to this, more or less.
- Invoked in Arthur C. Clarke's Imperial Earth by an Earthman who remarks wistfully that it'll be kind of monotonous "when" everyone on Earth has bred to "the same shade of beige." He's a touch envious of the main character's darker skin.
- Clarke is something of a fan of this trope, it seems, since in 3001: The Final Odyssey virtually everyone is described as having very mixed features, being some shade of brown, with names often not matching their appearance.
- In The Turner Diaries, it's implied via footnotes in 2099 everyone on the planet is the same race, that race being white. And yes, it's exactly what it sounds like.
- Invoked to a degree in Nancy Farmer's The Ear, the Eye and the Arm; modern races still exist, but there is a new minority of mixed ancestry known as (naturally) the Browns. One of the titular detectives is this ethnicity.
- In Robert A. Heinlein's The Moon Is a Harsh Mistress, the Loonies ancestors are from all parts of the earth, and everyone is of (very) mixed race.
- Dragonriders of Pern. It's never flat-out said in the series, but supplemental material notes that the humans living on Pern are more or less homogenous. Pernese are all somewhat tan in color, and the men have very little facial hair. Apparently, some extremes exist in eye and hair color. F'Lar is mentioned to have amber-colored eyes, while Lessa's are grey (which is something of a family trait in Ruatha Hold), and Kylara has blonde hair, to name three examples. This wasn't the case before they landed on Pern, though it seems that just about every major racial grouping was part of the Pern Expedition, and though there wasn't any kind of racism, people still tended to marry within their own nationality (Sallah Telgar and Tarvi Andiyar being a notable exception). Presumably that practice ended under the threat of Thread.
- Deliberately used in Across the Universe. Thanks to a combination of genetic engineering and a small gene pool, everyone on the ship Godspeed is Ambiguously Brown and has very similar facial features. In the first book, Eldest explains to elder that everyone was made one race to remove a potential source of discord. This means that when Amy (who is white and has red hair and green eyes) goes to live amongst the population, no one has any idea what to make of her.
- An attempt to invoke this occurs in Harry Harrison's "A Brave Newer World", where natural childbirth is on the downtrend and bottled babies are at the first stages of becoming the norm. The government program apparently figures that since they'll be growing the next generations, they can see about removing troublesome genes while they're at it. Unfortunately, their definitions of 'troublesome' includes many involving skin tone and eye shape. The doctor in charge of the project goes to great lengths to expose this bias towards Nordic and Anglo-Saxon ancestry.
- In the Great Ship series, only one character on the Great Ship is described as having distinct racial characteristics - Quee Lee - who is also the only character who was born on Earth before the emergency genes and ceramic brains became available; the rest of humanity spent the next hundred thousand years homogenizing.
- In The Giver, all humans in the Community are bred to more or less the same physical features. Differences such as Fiona's red hair and Jonas's blue eyes are regarded as a fault.
- The Tranhuman Army from MARZENA, also sometimes known by some as the TAR, and by others as Transhuman Nazis, is home to a secret occult group who believes that following the teachings of the Transhuman Seeder will lead to the eventual creation of a true Master Race. Homo Sapiens is dead, Homo Animus will reign supreme!
- In Rangers At Roadsend the protagonists visit a temple, where saints from the distant past are portrayed with green or blue skin, an exaggeration of the known fact that people were more diverse in the past. It is not clear how far the once race thing goes, but the surnames make it obvious that all cultures have mixed - people with all sorts of European and Asian surnames live in the same setting, and have been doing so for a long time. "Yellow hair" is mentioned as an exotic thing that happened in the past.
- Played with in the Honor Harrington series; while racial mixing is exceedingly common in the setting's 41st Century and generally speaking someone's name or where they're from doesn't necessarily give any indication as to what they might look like, there are exceptions. Manticore's Royal Family, the Wintons are (except for people who join it by marriage), what we'd call black or African. It's implied that the genetic engineering the Wintons carry made their features a dominant trait. Similarly, many planets were specifically settled by people from specific ethnic groups or from locations on Earth, and generally remained isolated for some time, thus in the series present retain recognizable racial groupings. The majority of the population of the capital world of the Andermani Empire, Potsdam, were ethnically Chinese, but they have German names and speak German. The Havenite planet of Prague had been originally settled by white supremacists, with a resulting white population. The Mfecane System was settled by black supremacists, although ironically environmental conditions selected for albinism, so the majority of the population has light skin, light hair, and light eyes with sub-Saharan African features.
- In The Spiral Wars, we are informed that most humans are just somewhat brown, but many characters are still specifically one race. The main Character, Erik Debogande, is African, and one Major character, Major Trace Thakur, is specifically of Nepali ancestry.
- It's not quite this trope, but Jessica Alba was chosen to represent a "perfect human" in Dark Angel because James Cameron commented that he was tired of the representation of an ideal human as one with "Aryan" features and that there would likely be evolutionary benefits in someone who was a mixture of ancestries.
- In Star Trek: The Original Series, Khan Noonien Singh has an Indian name and a Mexican accent/appearance, and is the result of an attempt to create genetically superior humans.
- In the BattleTech games, the major nations are highly multiracial and multicultural. In an Expanded Universe novel, a green-eyed redhead uses the alias "Rabbi Martinez" without arousing suspicion.
- According to some versions of the Warhammer 40,000 Back Story, this actually did happen to humanity for a while during the Dark Age of Technology, but during the Age of Strife various populations became isolated from each other for long enough that natural selection caused them to develop into different ethnic groups again. People who expressed more genes from their black African ancestors survived better on the hot planet of Nocturne, home of the Salamanders chapter, while on ice worlds like Valhalla or Fenris, selective pressures favored people who more closely resembled ancestors who came from colder parts of Earth, like Russia or Scandinavia. Meanwhile, high gravity planets and other environments that didn't exist on old Earth gave rise to new peoples like the Squats.
- Blood Bank features a post-apocalyptic society where vampires reign supreme. Humans as a whole are swarthy, with dark skin and eyes, and a gray-eyed human is considered enough of a rarity to be sold as a slave to bourgeois vampires.
- Real Life Comics referenced this trope, as main character Tony claims that this is his race.
- The hoax Disappearing Blonde Gene, allegedly a report by the World Health Organization which turned out to be a hoax. As Snopes points out, this prediction is Older Than They Think.
- In Orion's Arm it is stated that modern-day races only exist on certain baseline reservations, and most are genetic recreations. Of course, humanity isn't even one species anymore.
- The Straight Dope take on the plausibility of the trope.
- The future people, or "Goobacks", from the South Park episode of the same name, provide the page image. Much like how their race is a combination of every present-day race, their language is also a combination of every present-day language and sounds like unintelligible grunting. Combined with the fact that they are all bald (even the women), this makes them seem so alien to present-day folk that "future person" becomes classified as a separate race altogether.