Darwinist Desire

Characters with a Darwinist Desire only value one thing in potential mates: their perceived genetic fitness. They don't care for love, sexual pleasure, personality (except as it relates to their genetic suitability), money, or social status. Then again, social standing probably is identical or strongly linked to their genetic desirability, and their genetic superiority is assumed to make acquisition of wealth a given.

They can be very ethical about their interest, but the creepy factor of this trope can be played up if they're also an Evilutionary Biologist or The Social Darwinist. Even if they're neither of those, some characters aren't above acting like a Stalker with a Test Tube if their intended partner refuses to marry or mate with them. Darwinist Desire can manifest in both individuals or entire cultures/species, and while some depictions of this trope involve mating the "old-fashioned way", LEGO Genetics and Designer Babies aren't off the table. The preference may be dictated either because of culture (valuing "true" natural selection, for example) or because of a pragmatic lack of (mad) science skills. It's also worth noting that Darwinist Desire can be broadly or narrowly focused on traits; some may favor overall fitness, or specific traits like physical ability, beauty, intelligence, or even nose size.

On an individual level, the goal tends to be to have children fit enough to survive (or master) the world. On a societal level it may be to go up in terms of Evolutionary Levels, create Super Soldiers, or gain Psychic Powers. To some extent, sexual selection takes this path — many traits which represent fitness are selected for by partners, though mostly without conscious purpose in the case of most animals (and most humans). In Xenofiction, this trope can be a bit more justified, as the characters therein are usually non-sapient and non-human.

This trope is generally known as Eugenics. The practice is now viewed with some element of disfavor, partly because it's still very imprecise, but mainly because of its more extreme form, as practiced by the Nazis, which goes as far as "culling" those whose genes are deemed to be "inferior", such as the disabled or "lesser races".

Sub-Trope of Chosen Conception Partner and Pregnancy Does Not Work That Way. All Amazons Want Hercules may resemble a downplayed, specifically combative version of this trope.

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Examples:

Anime & Manga

• Since one of the plans of 7 Seeds project involved repopulating earth again after meteorites struck the planet, this is to be expected. Team Summer A is mostly brought up with the idea of having children with other specimen who are bound to produce strong offspring.
  • Ayu observes Aramaki and sees him as a great potential mate thanks to his looks, likable personality, and athletic skills and build. She doesn't seem to really see him as a potential love interest as well, though that might be changing.
• High School D×D has this as the starting point for several members of Issei's harem, such as Xenovia and Kuroka due to his status as a dragon. While a future children set series of stories do prove that having very strong children is quite achievable both gain reasons to be attracted to Issei beyond strong children as part of the story.
• In The Irregular at Magic High School, a magician's family chooses their spouse, and usually their choice is based on who will strengthen the Clan's bloodline. This causes a lot of unrest among the younger generation of magicians, but some genuinely buy into their parents' philosophy.
• In Kengan Ashura, the Kure Clan are able to keep their line filled with powerful fighters due to selecting exemplary physical specimens for mates. This is also the reason why Karla Kure is completely obsessed with Ohma as she sees him as someone who can grant her a powerful heir.
• The Mucbak in Level E are stated to find mates from other species this way.
• My Hero Academia: Possibly subverted with Endeavor. Word choice gave the interpretation that he only married Rei to have a child with Combo Platter Powers who could be strong enough to surpass All Might as the greatest superhero. However, it's later revealed he chose her to have someone balance his Quirk's weaknesses.^note The weakness being that Endeavor is only resistant to the heat of his own flames, not immune. Going too hot for too long will overheat his body. That, alongside the revelation that he originally chose Toya as his successor because Toya's Quirk gave him even hotter flames than his father's and the fact that he and she would've become parents at just out of adolescence and thus the start of his career, makes this much more questionable.
• In Peter Grill and the Philosopher's Time, most of the title character's Unwanted Harem are after him because he's the World's Strongest Man and they want to have his children under the presumption they'll be equally strong.

Comic Book

• Avatar: The Last Airbender - The Search revealed that Prince Ozai only married Ursa because Fire Lord Azulon and the Fire Sages believed that combining the bloodlines of Avatar Roku and Fire Lord Sozin would produce powerful firebending offspring for the Royal Family.
• Batgirl: The titular villain of the The Attack of the Annihilator storyline wanted Batgirl as his partner to repopulate Gotham City, seeing her as a good complement to his enhanced intellect and psychic abilities.
• Batgirl (2000): Cassandra Cain is the product of this trope. David Cain sought out Lady Shiva to have a child solely to be able to raise the strongest assassin in the world.
• Red Robin: The Daughters of Acheron kidnap Tim so that the elder of them can rape and kill him after she decides he's unknowingly proven himself to have what she wants in the male genetic donor of her progeny and fit the requirements for the sacrifice she's been looking to make for years in order to gain more mystic powers.
• Shang-Chi's Archnemesis Dad made sure to choose a woman with powerful genes as the boy's mother.
• Maxima from the DC Comics Superman titles. She is known for searching for mates among Earth's superpowered male population; as a result, Superman becomes her obsession.
• In X-Men, Nathaniel Essex's primary motivation is to create the ultimate mutant from the union of the Grey and Summers bloodlines, partly for the sake of it, partly to use as a weapon against his erstwhile master, Apocalypse. In the mainstream reality, he did this via cloning Madelyn Pryor from Jean Grey and setting her up with a grief-stricken Scott Summers, resulting in the conception of Cable. While Cable was immensely powerful, he was infected with the Techno-Organic Virus, which usually meant that he couldn't go all out. In the Age of Apocalypse, he was more direct and created Nate Grey from Scott and Jean's DNA for the sole purpose of destroying Apocalypse. Since Nate didn't have Cable's handicap (though he did have an engineered genetic flaw), he succeeded.
• This is the basis for Recognition in ElfQuest, but it's a completely unconscious telepathic urge that takes no account of personal preference or pre-existing relationships.

Fan Fiction

• In the second part of The Heart Trilogy, the witch Andraya schemes to get Smaug (a dragon transformed into a human) to impregnate her daughter Freyja. She believes that the old magic of the Third Age's greatest fire drake combined with the magic stored in her otherwise normal daughter will make the offspring powerful enough to rival the wizards. The reason she's not planning to mate with Smaug herself is that she sacrificed her fertility to awaken Smaug from a coma.
• In A Sky Of A Million Stars: There is an underlying sentiment of this in the current Quirk society. While Quirk marriages like the Todorokis are no longer common, there is a trend of relationships and marriages ending because the resulting offspring did not have strong and/or optimal Quirks. One half of the couple would up and leave their partner and child(ren); if the partner had similar biases, they'd also abandon their child(ren), leaving the kid(s) orphaned. Hisashi left Inko and Izuku because of this mindset; as Izuku was Quirkless, he was therefore "weak" and couldn't bring honor to the family name.
• After usurping Equestria's throne in Loved and Lost, Prince Jewelius plans to marry Twilight Sparkle, expecting the powerful unicorn to bear him powerful offspring who'll continue his legacy. He admits to Twilight's imprisoned friends and brother that were he to find an even more powerful unicorn mare, then he might get rid of Twilight through an "accident" so that he can marry the other mare.
• My Inner Life does this by accident, with Jenna repeatedly musing on what beautiful babies she and Link could produce long before they're even really together. It's not meant to be a big part of her character, but with the shallowness of their romance, it can certainly feel that way.
• Pokémon Reset Bloodlines has Ash's Father, who sired Ash specifically because Delia is a descendant of Sir Aaron, and thus their child would be very powerful. He waited years for Delia to be born, as the lineage came from Delia's father. At the same time, he tracked down hundreds of other women across the world with Recessive Super Genes like Delia for the same purpose.
• Another example from a My Little Pony: Friendship Is Magic fic: Early in "Alicornundrum", from RealityCheck's Nyxverse, Lord Blueblood attempts to get newly coronated Princess Twilight Sparkle and Prince Blueblood into an Arranged Marriage so that "a proper, rightful ruler— one of unicorn blood— will be on the throne", which also means that they can disregard Nyx as a member of royalty. This goes pear-shaped before it can even begin, courtesy of Twilight, her parents, Princess Celestia, and Prince Blueblood all taking offense to this idea on various levels. Besides which, as Celestia points out in justified fury, the contract itself would've been illegal if Lord Blueblood tried to take it to court, whereupon he would've been convicted of contractual fraud, blackmail, statutory rape, pony trafficking, and treason against the Crown Princesses of Equestria.
• In Wish Carefully, after Harry Potter and his friends are able to prove to the rest of the global magical community what a load of bullcrap Pureblood Superiority is via showing how the Death Eaters' obsession with blood purity has led to inbreeding that is resulting in Generational Magic Decline with more Squibs being born in each succeeding generation (and the few magic users there are being so weak that they can't complete the traditional seventh-year courses at Hogwarts), magically powerful Muggleborns are being sought out as spouses for other Purebloods around the world who are looking to keep their bloodlines from becoming "too pure".
• In Witchcraft, Giovanni had Silver with Ariana because she was an exemplary member of Team Rocket who showed all the positive traits a Team Rocket agent, or even leader, should have.

Films — Animated

• In How to Train Your Dragon: The Hidden World, the Fury dragons' mating displays show off genetically desirable traits. One display involves the courted dragon sneaking through a human village: her suitor must be stealthy enough to follow her without waking any of the potential predators. Later tests involve hanging by one's tail from a branch (in the manner of bats) and dance-flying through a thunderstorm.

Films — Live-Action

• This is pretty much everyone's modus operandi in Gattaca. It's an interesting case because sentimental partners are chosen based on how good their genes are, even though couples (who were both already Designer Babies) would frequently repeat the process on their children, making such genetic discrimination either purely social or as a sign of continued financial success.
• In The Invention of Lying, marriage is based only on this. The romantic interest struggles with picking between this trope and her love of the protagonist. She chooses love, but if you think about it, being the only person able to lie is a pretty big Darwinian advantage.
• Iron Sky: Brought up by Klaus Adler as a rather unromantic way of telling Renate Richter that he wants her babies.
• In The Private Life of Sherlock Holmes, the ballerina Madame Petrova tries to get Holmes to contribute his DNA to her children, hoping that their offspring with have her physical advantages and his mental advantages. Holmes rebuffs her by insinuating that he and Watson are a couple.
• Species II: The aliens infect two members of the crew with a Face Full of Alien Wing-Wong, but leave the third astronaut unharmed. It's later revealed why when the hybrid Eve (who would jump just about any willing male to hijack their sperm and create more offspring) sizes him up and recoils in disgust. It's because the astronaut (who's black) is a recessive carrier for sickle cell disease.

Jokes

• There's an urban myth that Marilyn Monroe (or Isadora Duncan, or Sara Bernhardt, depending on who's telling the story) once propositioned Albert Einstein (or George Bernard Shaw, or Groucho Marx) with the question: "Don't you think that with my looks and your brains, we should have the most wonderful children?" Albert/George/Groucho responded, "But what if they were born with my looks and your brains?"

Literature

• While the protagonists in A Brother's Price seem largely unconcerned with this, the society as such caters to Darwinist desires. Probably due to inbreeding and genetic mutation being a common problem, (the fact that very few males are born hints to this) a prospective husband is checked for deformities and sperm count before the wedding takes place.
• The Abh in Crest of the Stars consider "I want your genes" to be one of the highest compliments you can give someone and is seen as something akin to a marriage proposal, considering they are all test tube Designer Babies.
• In Darth Plagueis, Darth Tenebrous had one of his agents seduce a Force-sensitive businessman, predicting that their child would be strong in the Force and would thus make an ideal apprentice. That child would grow up to be the titular Plagueis.
• In Digital Fortress, Hale has a few thoughts along these lines (feeling that the protagonist's genes would be wasted on her Love Interest while if he had children with her they would be "perfect"). Amongst other signs, he's a jerkass.
• In Dune, the Bene Gesserit actually have Darwinist Desire Matchmaking. They've been secretly manipulating the marriages of all the members of the noble houses to produce the Kwisatz Haderach, a being capable of omniscience.
  • God-Emperor Emperor Leto II continued this on a grander scale, however he created a line of people immune to being scryed through omniscience.
    • In the same book, one of Leto's warrior-priest women is so impressed by a nearly superhuman display of physical prowess and determination by a clone of Duncan Idaho (a favorite genetic source in Leto's program) that she achieves orgasm just watching him reach the top of an unscalable cliff. For that matter, the successful product of Leto's breeding program also has her eyes on Duncan (who is quite literally her ancestor several times over) as a good genetic match so she can pass on her valuable anti-scrying genes.
• In False Memory, by Dean Koontz, this is Claudette's reason for choosing Mark Ahriman to impregnate her with her first child when her then-husband proves infertile. She didn't like the sperm donor as a person but loved his genes. Unfortunately for the baby, she was born with trisomy 21 (Down Syndrome) and was murdered by her mother. The grudge between the bio-parents of the ill-fated infant is still affecting the lives and in some cases deaths of those in contact with either decades later.
• In the Horus Heresy it’s mentioned to be the modus operandi of one planet.
• Also noted in E.E. Doc Smith's Lensman series. In Galactic Patrol our hero's commanders assign him attractive nurses while he recuperates. The goal is to create an even better person if he should reproduce. Interestingly, the attractiveness they look for isn't just skin deep:
  "Look at that skeleton!"
• In Masques, the Big Bad, among other misdeeds, rapes a shapeshifter woman, in order to use the resulting child for his evil plans. His end goal is to achieve immortality, for which he needs the shifter's superior healing ability.
• In Roald Dahl's novel My Uncle Oswald, Oswald collects the sperm of geniuses in order to sell it to women who want to have genius babies.
• Princesses of the Pizza Parlor: How new witches are born from current witches, with the quality being chosen by the mothers as "good magic backgrounds" as said in the third episode:
  "I didn't know wi... your people had fathers." said Cassie. "You all seem to be girls." The cleric blushed with embarrassment.
  "Oh, we got fathers," said Bianca. "We just don't have much to do with them. Our moms pick guys with good magic backgrounds, have us, and then they're gone."
• Justified in Raptor Red, since the character is a Utahraptor. She rejects a yellow snout raptor who tries to court her, despite being another subspecies, and later, another suitor is rejected because he has parasites. Eventually, she is persuaded by a red snout male to pair up. Her thoughts are that he's strong and smart. Another female, meanwhile, keeps getting rejected because she's freakishly big and the males sense something wrong.
• In The Ship Who..., people commonly bank sperm and ova upon their majority, and it's noted that there are cases of individuals who are particularly noted for intelligence and capability getting deluged with requests for their gametes so that people who admire them can have their babies.
• Somehow Played for Laughs in a spinoff of the Tantei Team KZ Jiken Note series. After several years of Time Skip, Aya's mother mentioned she wants Aya to marry off to one of her male friends that Aya herself stills considers as Just Friends. In the ensuing conversation, the mother mentioned an advantage of marrying Uesugi is "his genes."
• The early days of the Howard Families (from Robert A. Heinlein's works) were pretty much "your family is long-lived, my family is long-lived, let's have long-lived kids together and get the money offered by the Foundation". In Time Enough for Love Lazarus Long, the oldest human on record, finds that there's still a bit of that attitude among the Howards when several women (most of whom are his descendants) ask to bear his children.
• In the Uplift series eugenics programs are a standard part of uplifting new species. Earthclan chooses a "card" system for their clients with green, blue, and white cards (unrestricted breeding rights) awarded to scientists, artists, war heroes, etc.
  • At the end of The Uplift War Fiben gets annoyed that now that he has a white card every female chimpanzee on the planet wants his genes, and his wives (themselves white and green) aren't helping much.
  • Also, at puberty all clients have a gamete sample taken and frozen, and are then surgically sterilized. If they get a green card or higher their fertility is restored, otherwise they have to have kids by IVF and are often required to adopt children produced with higher-rated gametes in addition to or instead of their genetic offspring. Red cards aren't allowed to reproduce at all, and Probationers aren't even allowed to be near children.
• Villainess Level 99: I May Be The Hidden Boss, but I'm Not The Demon Lord: A lot of world renowned and prestigious families want to have their sons marry Yumiella due to her incredible power due to being level 99 in a world where the next highest level is 60. Yumiella, wanting nothing to do with such squabbles, claims any potential suitors must Best Her to Bed Her to get them off her back.
• Vorkosigan Saga:
  • Cetaganda, an insular society with transhuman aspirations where virtually all reproduction (at least among the Ghem and Haut classes we are shown) is the result of inter-clan negotiations and parents may not even live on the same planet. The ruling Haut class are virtually posthuman already. Unlike most examples of this trope they recognize that each child is still an experiment despite all of the planning that goes into creating them.
  • The first generation Quaddies, being effectively slaves, had their breeding partners chosen for them. Gaining the freedom to choose their own mates was a belated inducement in their rebellion—belated in that they didn't even think of it until after they'd already started rebelling.
• The all-female dryads in The Witcher series mate only with (human) men whose genes will strengthen their race. This also makes them utterly uninterested in getting it on with the eponymous witchers, who are all sterile (although Geralt can woo a dryad in The Witcher game by pointing out that sex is good for health, too).

Live-Action TV

• Nietzscheans in Andromeda are a species of Social Darwinists who compare pedigrees when courting. Tyr married a member of a Pride his crewmates were fighting after he attracted her attention by besting one of their strongest warriors. And even after he left her and forced her Pride to leave their home she decided to keep his child (their relationships move quickly), in part because in defeating them, he had shown himself to be extremely cunning and capable. The episode has the Pride's matriarch put a clear distinction between being a worthy husband and a worthy father. By outsmarting their Pride, he proved that his genes were good. Therefore, he's worthy of being a father. But by betraying his wife's Pride, he has shown to be an unworthy husband. They also practice polygyny (the multiple wives kind of polygamy), since it's the fastest way for a worthy male to spread his genes.
• G'Kar proposes this to Leeta in Babylon 5, on the grounds that their children might create the first Narn telepaths. Given that G'Kar is later indicated to have a fetish for human women, however, his goals were probably more than purely Darwinian.
• Better Off Ted: In one episode Viridian Dynamics attempts to invoke this by publishing a list of "most genetically compatible employees", though their main motivation is preventing employees from taxing the health plan with unhealthy babies, and most pairs prove to have less-compatible personalities.
• On The Big Bang Theory, when the guys meet Sheldon's sister and all want to try and date her, one of them makes the mistake of getting Sheldon involved by convincing him he should care who his sister may end up producing children with since they share genes (on the hope that the offspring might be a genius like him). Sheldon of course, gets way over-involved in determining which, if any, of his friends would be the best genetic match with her. When she finds out, she makes her feelings known to Sheldon... by kneeing him in the groin.
  • Leonard sees this in his pursuit of Penny:
  Leonard: (gazing wistfully at Penny) Our children will be smart and beautiful.
  Sheldon: Not to mention, imaginary.
  • Later Sheldon gets a girlfriend in his Distaff Counterpart Amy Farrah-Fowler. Both agree that the combination of his genes will create the first child of a lineage that will eventually bring humanity the perfect world leader. Of course, they consider themselves above the gross act that regular humans use to procreate. They are going with the test-tube and Sheldon wants to know if Penny rents her womb. Though later on they both get some Character Development and have sex at least once.
• In Bones, Dr. Brennan initially justified her interest in having a child with Booth by claiming he possessed favorable genetic traits that would complement her own, she later decided she wanted to have a baby via IVF and decided that Booth had the best genes for it. Then the plan went by the wayside when Booth was diagnosed with an early-stage brain tumor. They end up having sex, with Bones accidentally getting pregnant and have a daughter. Later they also have a second child after getting married.
• Law & Order: SVU: "Design" has Dr. McManus freely admit that he'd chosen his wife based on her perceived genetic qualities, in hopes of having the best child possible. He also opened a fertility clinic for people seeking the same thing, with the "best" sperm from men with high IQs.
• A made for TV Skiffy movie about a post-disaster society had as one of the gimmicks colored patches one wore to indicate which partners would make good genetic matches with the expectation that one would mate within one's color grouping.

Tabletop Games

• The Warrior castes of the Clans in BattleTech practice eugenics. A Clan's scientists blend together the genes of two "honored" (oftentimes dead) warriors and grow about a hundred kids in tanks, of which as few as five may finally be considered to be the much-desired warrior-material, with the rest either dying in the process or (usually) being demoted to a lower caste.

Theater

• Zeroth Law Of Trope Examples: In Henry V, Hal tells Catherine "thou must therefore needs prove a good soldier breeder."

Video Games

• In Assassin's Creed: Odyssey, this is the reasoning given by developers as to why a Misthios would end up conceiving a child with the designated love interest in the "Legacy of the First Blade" DLC regardless of player choice: Since said love interest was of a strong Isu genetic lineage, the Misthios decided that they were obligated to further said genetic destiny. This very line of thinking was also responsible for the Misthios' own parentage, as their true father is Pythagoras, who bore a child with the daughter of Leonidas I due to her family's DNA.
• One viable strategy in Crusader Kings. When looking for a husband or wife (either for you or for your children), many players forgo looking for alliances or prestige. Instead, they look for partners with good genetic traits, genius being the most sought after. Of course, it's not impossible to find a partner with good traits, prestige, and a good alliance.
• EXTRAPOWER: Attack of Darkforce: This in general is the desire of the bem, a parasitic space organism that came to Germany on a meteorite. Apart from the general survival and propagation of their species by assimilating humans, they seek out superior genetics where they can to produce superior offspring. Francisca identifies Gradius as having superior enough genetics that the two of them should become mates, but his assimilation of a young boy Hans gave Gradius his romantic feelings for the girl who used to be Martina, putting conflict between him and Francisca. The bem eventually capture another human with superior cells, assimilate him with exceptional bem, and produce Gael Bolg, the apex of their species.
• Fire Emblem
  • Fire Emblem: Radiant Dawn reveals that Ashnard, the Big Bad of Path of Radiance, married Almedha of the Dragon Tribe purely in hope that their child would inherit tremendous power. Not only did their son turn out to have no particularly special powers, but conceiving him caused Almedha to lose hers, and as a result, Ashnard disowned both of them.
  • Deconstructed in Fire Emblem: Three Houses. The noble families of the Holy Kingdom of Faerghus are only interested in their children bearing a Crest and marrying someone who also bears a Crest. This has led Sylvain, who comes from Faerghus, to hate the fact that he has a Crest because his older brother Miklan didn’t, and he bullied him throughout his whole life.
    • The third wave DLC reveals that this was what led to the birth of the Death Knight. Mercedes’ mother had married the baron of House Bartels shortly after her birth father died, and sired him a son, Emile/Jeritza, who bore a Crest. Sometime later, Mercedes and her mother fled to Faehrgus while Emile stayed behind to protect them. When Emile’s father found out that they were living in a church, and that he intended to marry Mercedes for her Crest because her mother was past childbearing age, it caused Emile to snap and kill his father, along with everyone else in House Bartels. Emile could not remember what happened that day, only that it led to the creation of his Superpowered Evil Side, the Death Knight, to try to protect Mercedes.
• The salarians in Mass Effect keep records of their family's genetic pedigree for exactly this reason. Their species doesn't really connect the concept of sexual desire with reproduction, since, as amphibians, they reproduce via external fertilization.

Webcomics

• In Dan and Mab's Furry Adventures, it's stated that for demons fighting arenas double as speed dates. For instance, Kria really can't help herself when she meets Dan.
• In Freefall, Florence theorizes that the reason so many women fall for bed-them-and-leave-them jerks is that they subconsciously want children who will spread their own genetic material the same way. Though Florence herself is dating a nice (and rather well-toned) guy with whom she has no chance of blending genes.

Web Original

• SCP Foundation: SCP-ES-091 it is a small abandoned town in the south of Chile where "something", possibly paranormal, affects people with high intelligence and good genes, prompting them to have sexual relations with each other. On the other hand, people with low intelligence and/or who carry a genetic defect instead receive strong suicidal impulses.

Western Animation

• Zoidberg's people in Futurama do this, with Zoidberg's main love interest for that episode flat out telling him that she isn't interested in him because he's an "inferior male specimen".
• Subverted in Gargoyles, as when Xanatos proposes to Fox he tries to justify it with how they're a genetically good match, and when she asks about love his response is "I think we love each other; as much as people like us are capable of that emotion." But by the end of the episode, he's surprised himself with the fact that he truly does love her.

Real Life

• Truth in Television. It's just not done consciously (many signs humans and other animals find attractive have been found to correlate with fertility and other desirable traits). Though it should be noted it is not exactly done subconsciously either, it's done biologically. There is no mechanism for organisms to evolve a knowledge or desire of spreading genes, consciously or otherwise. Just simpler behaviors like desiring sex. But being attracted to people with exterior signs of fertility and other desirable traits is an evolutionary advantage over being attracted to infertility. So, based on the Trope Namer's theory of evolution, in the long term, the genetic basis for biological factors that cause such attraction are more likely to perpetuate in a species' genome.
• In evolutionary biology, this is referred to as "good-genes sexual selection". It's not the only factor that determines mate choice, though. For example, a female may choose a male who holds lots of resources that can be ploughed into their offspring, even if he came by those resources by chance rather than on account of superior genes.
• Also, "eugenics" is what you'd call it when the traits are being selected for deliberately (and they may not even correlate with real genetic fitness) rather than by unconscious instinct.
• Note that historically, actual eugenics programs were not necessarily good at determining genetic fitness. The Nazis believed in a "master race", but as anyone with an understanding of genetics can tell you, the most genetically superior individuals tend to be mutts, involving a principle called 'hybrid vigor'.^note Which is not quite so, as a "hybrid" advantage lays mostly in the lack of genetic defects, simply breeding two people from two different races won't magically create a baby with Superman's strength but it will drastically lower the chance of recessive genetic diseases which is the overwhelming majority of them, the more so the more the parents are genetically different from one another. Now "race" is a totally discredited biological concept and there is no meaningful biological definition of it, as can be seen by the fact that there is more genetic diversity within Sub-Saharan Africa (which the Nazis considered to be inhabited by one single race) than between Sub-Saharan Africa and the rest of the world. So yes, highly genetically different parents may very well both be "black", but they will likely never both be "white". In other words, race has so little to do with genetic superiority that the Nazis were actually right about interbreeding in some cases, for the COMPLETE opposite reasons of what they proposed.
• Historically, eugenics has been associated with racist pseudoscience for a good reason—it is nothing but racist pseudoscience (with a dash of dehumanization for the disabled thrown in also). Prior to the mapping of the human genome, there was no scientific basis for any of it beyond "we don't like people who look like you". And now that the genome has been mapped, we know that it is far too complex to be amenable to the eugenicists' tinkertoy concepts of how inheritance works and virtually no one is "pure" anything due to a lot of undocumented variability (e.g. screwing around) in even the most documented royal pedigrees. And this impureness, it should be stressed once again, is a good thing. "Keeping the bloodline pure" - and dynastic marriages - ultimately produced such genetic defects as the "Habsburg jaw" or the extreme prevalence of hemophilia in the royal houses of Europe just before World War I and in Ancient Egypt "keeping the bloodline pure" was even used as justification for royal Brother–Sister Incest. Moreover, ultimately humans have the same ancestry, and thus none can be called "pure" white, say (we all descend from African ancestors if you go back far enough).
• In a biography of Shirley Temple there is an account that women would proposition her father (who looked like her), hoping to get a Shirley of their own. They may not have actually meant it but her mother wasn't pleased.
• This is the tongue-in-cheek reason for the so-called "D-1 babies": When heterosexual athletes of high ranking collegiate sports ("Division 1") are in each other's social circles, they're supposedly more likely to hook-up and have kids with similar advantageous traits (taller, stronger, whatever). While that sometimes could happen, actual genetics does not work that simply.

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