Interbreeding between ethnic groups within a race, or between multiple races in fantasy or science fiction, is a popular activity. But what happens when the resulting babies grow up and start breeding themselves? You might end up with a Heinz Hybrid, or just someone who's mostly A with a little bit of B.
Historically, the One Drop Rule assigned these people to the lower-status group. Someone in the American South who looked Caucasian but had a distant Negro ancestor would be classed as "black". On this wiki, the One Drop Rule expands to cover interracial and interspecies as well as inter-ethnic lines of descent.
There are two features that must be present for a character to fall under the One Drop Rule:
- The character's "other" ancestry should be distant — a grandparent at the most recent.
- The character should be the target of bigotry/discrimination as a result of the "other" ancestry.
For example, Spock gets a lot of grief from Vulcans due to his 50% human family tree. But he's a Half-Human Hybrid, and would stay on that page instead of moving here. If Spock were to marry another Vulcan, his children and grandchildren note would fall prey to the One Drop Rule.
Compare to Half-Breed Discrimination (when there's more than just one drop) and Uneven Hybrid (when the one drop doesn't result in any discrimination) . Contrast to But Not Too Black. Revealing that a character falls under the One Drop Rule can result in a Pass Fail.
- In Fullmetal Alchemist, Major Miles is one-quarter Ishvalan from his maternal grandfather's side. During the Ishvalan Civil War, when Executive Order Number 3066 came down, stripping any soldiers of Ishvalan ancestry of their commission and imprisoning them, his superior officer Major General Olivier Armstrong disobeyed and kept him with her at Fort Briggs specifically because he offered that perspective. And despite only being a quarter Ishvalan, Miles has the two most distinct physical markers of the ethnicity in his white hair and red eyes, the latter of which he usually hides with tinted glasses.
- A parodic inversion in Blazing Saddles. When the foreman of the railroad gang says he wants "a couple of niggers" to check for quicksand, Bart points out that his grandmother was Dutch and therefore he wasn't entirely Black.
- C.S.A.: The Confederate States of America:
- After annexing the Union, the CSA passed the 'One Drop Statute' that decreed that if a person had any degree of black ancestry-regardless of if they were pale skinned or even if they had gotten their freedom-they were to be forced back into the slave stock.
- This would have consequences for John Ambrose Fauntroy V decades later as a result of the 'One Drop Scandal' in which his slave Horace accused him of having black ancestry, telling of how Fauntroy's great-grandfather had sexual relations with Horace's great-grandmother, then took the light skinned children away and 'made them white' while the dark skinned ones were left to be slaves. The resulting accusations and scandal cost Fauntroy the presidency, and he shot himself not long after the election. DNA testing done after his death proved 'negative' but the Mockumentary doesn't clarify what 'negative' means in this context.
- Free State of Jones: Rachel is mixed race. It becomes an issue at Davis Knight's trial as to whether his great-great grandmother was Rachel or Serena Knight. Assuming the former, he would be "colored" under Mississippi state law and thus forbidden to marry a white woman. If the latter, he would be white and thus freed. The prosecutor lampshades how unusual this is, as generally it would be the father whose identity isn't clear. Eventually the Knight family Bible is uncovered, revealing that it was Rachel.
- Ellery Queen's The Roman Hat Mystery. The murder victim had turned blackmail into a career. Which secret drove one of his targets to kill him? The revelation that he had a distant Negro ancestor.
(He) has just a drop in his veins — just a drop, but it would have been more than enough ....
- In the story "The Color of Honor" by Richard Connell, a Klan leader discovers that his grandfather had an affair with a "mulatto" woman, but passed the resulting pale baby off as the child of his lawful white wife. That baby was the Klansman's father, and therefore he himself is a Negro! And as such, he must now fight against the Klan, as is only honorable.
- The original "one drop rule" kicks off the plot of Mark Twain's novel Pudd'nhead Wilson. A woman has enough white ancestry that she could have passed for white herself, but she's still confined to a life of slavery on a Southern plantation. She bears the plantation owner's son, who looks even whiter than she does — then she switches her son with the plantation owner's other, legitimate son, so that her boy can live a life of privilege.
- Brother Paul, the hero of Piers Anthony's Tarot series, is one-eighth black and looks white. Part of his pilgrimage in the Tarot series is a realisation of his black ancestry and how racists blighted the lives of his immediate ancestors - and how his adoptive parents held it against him. It comes to the fore in one surprising way: he finds himself alone and friendless in a black ghetto, facing down people who refuse to believe he has any black ancestry at all and who are prepared to treat him as a white boy in the wrong part of town. He has to prove his credentials, and does so by winning a rapping contest.
- Lampshaded and made a plot point in Sidhe Devil. The story kicks off with Doc being abducted for his seed because he's pure-blooded Daoine Sidhe and his half brother and step-mother, who are in on the plot, secretly aren't due to the one-drop rule.
Doc: I cannot imagine being so devoted to a matter of race that you would lie about it for so many years and suffer to conceal some wayward drop of blood in your ancestry.
- Laura from Sarny is only 1/8th black but has to hide that in order to get anywhere in the post-Civil War era. She's able to pass as white by just covering up her curly hair.
- J.K. Rowling has stated that the one drop rule is in effect with the most ardent of the pureblood supremacists in the Harry Potter series. Even though a "mudblood" or muggle-born is normally considered someone who is born of parents who aren't wizards. Therefore even though Harry Potter's parents are both wizards, someone like Lucius Malfoy would still consider him tainted due to his mother being a muggle-born.
- "Talma Gordon": Though Isabel is only one-16th black and her daughters one-32nd, it's enough for them to be discriminated against by those who know the truth.
- Discussed in To Kill a Mockingbird. At one point, Jem points out a mixed race child (the son of Dolphus Raymond and his "coloured woman") to Scout and Dill, who think the child looks black and ask Jem how he can tell the difference. Jem says you can't always tell if someone is mixed race unless you know who their parents are, prompting Scout to ask her brother how he knows they "ain't Negroes". Jem replies that there is no trace of African blood in the Finch family as far as Uncle Jack knows, but they might have come out of Ethiopia in Old Testament times. Scout thinks this means it was "too long ago to matter", but Jem says that, in the eyes of their segregation era Deep South community, having even a single drop of African blood "makes you all black."
- In Agent Carter, the very white Jarvis is not allowed into a whites only social club because "[his] father was 1/8 Turkish."
- Invoked in one episode of All in the Family. Archie is recruited into a new social club that turned out to be a front for the Ku Klux Klan, and once he learns this he wants out. He eventually tells them he has "black blood"note .
Mitch: There's a whole lot of us, Bunker.
Archie: Well let me tell you there's a whole lot of us.
Mitch: "Us" who?
Archie: Us blacks.
- Mixed race Bette and fully black Yolanda on The L Word discuss racial politics, and at one point Yolanda brings this up to tell Bette why Bette is still considered 'black'. Bette retaliates by asking if she's going to let White America define her identity. Bette notes that she could pass, but never does, consciously embracing having black heritage and always calling herself biracial rather than to deny either of her parents implicitly.
- mixedish: This trope is discussed by Bo with her voiceover, noting that in the US anyone with (visible, at least) black ancestry gets classified as black. She's not comfortable with that, however, preferring to embrace both sides of her heritage and call herself mixed, while her siblings "pick a side" based on their looks.
- Played for Laughs in an early episode of Mad TV with a man claiming to be an Octoroon, an antiquated term meaning someone who is 1/8th black, meaning his whole family tree is white except for one great-grandparent. Despite looking completely white, he still insists on acting like an oppressed black man.
- Jazmine DuBois from The Boondocks, who's the daughter of a white mom and a black dad. She feels very confused and insecure about her biracial heritage, and so she's really annoyed by Huey Freeman immediately labeling her as only being "black". Later when her teacher and principal learn that she's mixed race and they inquire further about it, they eventually come to the same conclusion as Huey.
- Dungeons & Dragons:
- AD&D 2nd Edition went there with half-elves right in the Player's Handbook, where the children of a half-elf could only ever be a half-elf themselves or else essentially human with some cosmetic elvish features depending on the other parent, but never an actual 'proper' elf. This isn't even presented as prejudice (which could vary by setting), but just as biological fact.
- In 4th Edition lore, the ancient, decadent Empire of Bael Turath became the first Tieflings through a collective Deal with the Devil. While tieflings can interbreed normally with humanoids, the children are always tieflings, no matter how small a fraction of Turathi blood is in their ancestry; and those children get to experience the full gamut of distrust and prejudice that their "devil-tainted" pedigree attracts.
- In a more positive example, the sorcerer class. It requires some sort of magical ancestry (dragons being a popular explanation), but not necessarily to a degree of being a distinct "race" such as dragonblooded or aforementioned tieflings. One drop is enough to grant magical powers.
- Leviathan: The Tempest: A single Leviathan in your ancestry, even many generations back, can be enough to make you a Hybrid or even a full Leviathan. The heritage can even pop up along a line of descent which has produced completely normal humans for the past couple of generations, which quite often means a full Leviathan being born to parents who are completely ignorant of their monstrous heritage.
- Invoked in Show Boat. Steve is white, and his wife Julie is mixed-race, passing for white — their marriage was a crime in the South at the time. When someone tips the local sheriff off and he comes to arrest them, Steve quickly cuts Julie's hand and swallows her blood; when the sheriff arrives, he asks, "You wouldn't call a man a white man that's got Negro blood in him, would you?" He swears to having that blood in him, letting the sheriff assume this trope is in effect and Steve has been passing for white; the two are able to leave the boat, and the South, in peace.
- In the Dragon Age universe, the offspring of an Elf and a Human is always a human. There is absolutely no difference between an "Elf-blooded" human and any other human being, but being Elf-Blooded is considered a major shame. So much so that when it's discovered that an Empress's personal Champion is Elf-Blooded, she exiles him before the scandal can damage her political career.
- And as revealed in one of the novels, this is also one of the reasons it was considered important enough to cover up Alistair's maternity. His real mother is not only an elf but Mage and a Grey Warden, none of whom are liked in Ferelden, so he was raised to believe his mother was a castle servant who suffered Death by Childbirth. Especially since he can potentially become the King of the entire country, since his father was none other than King Maric.
- In Not Tonight, Britain is under the rule of a xenophobic far-right nationalist party, and large portions of the population have had their UK citizenship revoked because they have at least one non-British citizen as their parent or grandparent.
- In Fire Emblem: Path of Radiance and Radiant Dawn, anyone with even a single Beorc/Laguz relation in their ancestry can be born a Branded, who are looked down on by both races.
- In Gunnerkrigg Court, Antimony Carver stopped being considered a human when it was revealed she had a fire elemental in her ancient ancestry. Subverted, though, since both "sides" want to claim her instead of rejecting her. Furthermore, the waters are a bit muddied between this trope and Half-Human Hybrid as that ancestry doesn't get diluted - the fire passes wholesale from the mother to the (always only one) child.
- Virginia's "Racial Integrity Act of 1924" split Virginians into "white" and "colored". And then the lawmakers realized they had a problem on their hands — many of the Virginia elite claimed descent from Pocahontas, and as written this law would have redefined them as "colored". In the "Pocahontas Exception", a person who was 1/16th American Indian was legally considered white. (The same fraction of any other ethnicity classed you as colored.)
- Under Nazi Germany's notoriously anti-Semitic Nuremberg Laws, a person with one Jewish grandparent was Mischling Second Degree, with limited legal rights. The SS was even stricter — if you wanted to join, you had to prove that all your direct ancestors going back to 1750 were non-Jewish. Depending on how long one considers one generation to be, this could involve proving Aryan ancestry back 8 or 9 generations. However, given that the records used contained religion and not ethnicity, one could even have had completely Jewish ancestry and be classified as full "Aryan", if all your (distant) ancestors were converts. Of course, it's moot since their racial theory was nonsense-European Jews have a lot of shared DNA with other groups there since (by intermarriage or affairs) mixing occurred historically anyway very often.
- Northern abolitionists took advantage of this trope in the antebellum period. They would stage mock "fancy girl slave auctions", and gradually put lighter-skinned women on the "auction block" until finally they were showing off women who were outwardly pure Caucasian but had the necessary one drop of black ancestry to be classed as black in the slave-holding South.
- Maynard Jackson was unironically seen as Atlanta's first black mayor when elected in 1973. In Europe he'd probably would have been considered as a swarthy white guy.
- Meghan Markle had an infamous controversy about her ancestry after marrying into The House of Windsor, despite that she could convincingly pass for -at most as swarthy- white anywhere. In Europe, at most, she could be easily believed to be mediterranean.
- Barack Obama is widely seen as, and identifies as black, despite his mother being white.
- A school teacher showed photos of Obama to her class and asked them to point which features looked "African". Several of the chosen ones were actually shared with his white grandfather◊. In Kenya, where Obama's father was from, he would be considered white◊.
- The conspiracy theory about Obama being born in Kenya and therefore not qualifying to be US president really exists only because of this. Not only was his mother white, she was also an American-born citizen (and one with a family history going back to the first settlers in Virginia, at that), so he would still qualify as a "natural-born citizen" even if he was not born on US territory.
- Elizabeth Warren had heard from older family members that they had Native American ancestry, and at times she identified as such in her professional and political life. When opponents claimed that she made this up to advance her career, she took a DNA test that showed Native American ancestry "in the range of 6 to 10 generations ago." To supporters, this proved that she was telling the truth, while detractors argued that being, at most, 1/64th Native doesn't really qualify one to claim that as your race. Since then, Warren has conceded that she doesn't have the cultural links to really identify as Native American. Legally in the US, one isn't deemed Native American unless they're enrolled with a federally recognized tribe, which requires ancestors who were also members (specifics vary by tribe).
- In many countries, like South Africa, Indonesia, Jamaica, Brazil and others, the trope is the opposite. There are distinct mixed race populations (in some cases many varieties), with people deemed to be just one race in the US not considered so there.