:: ''The fertility of a species is inversely proportional to its lifespan. Thus, as a species approaches immortality, their birth rate approaches zero.''

In many works of fiction featuring immortality, the immortals in question are sterile or infertile: they cannot have children. LegacyImmortality is both impossible and unnecessary.

In many cases, this is an example of CursedWithAwesome, because, along with some STDImmunity, it means that the teen-looking [[ReallySevenHundredYearsOld ancient]] vampire stud can get it on with the ladies as much as he wants without worrying about consequences of any sort, particularly leaving lovers pregnant with a {{Dhampyr}} who will eventually grow up and [[IHateYouVampireDad try to kill him]]. Or at least demand [[UndeadTaxExemption child support]].

Immortals may have methods of making mortals immortal (vampire bite, AppliedPhlebotinum, or the like) and they may come to view those that they bring over into immortality [[ParentalSubstitute as their own children]], teaching them the lessons and how to thrive as an immortal. This, however, is not the same as having natural children. It's more like adoption and a new immortal being HappilyAdopted is certainly possible.

Sometimes the beings in question are perfectly able to have children, but are not allowed to, by the laws of their society, because allowing immortals to breed will quickly lead to overpopulation. This usage tends to be found in [[MohsScaleOfScienceFictionHardness hard]] SpeculativeFiction.

Another common twist is to have immortals that are quite fertile/potent but whose children are completely or near-completely mortal. These examples are also included here because they fit in with the theme that unchecked reproduction combined with immortality is unsustainable. This aversion is probably even more tragic, since the immortal will then be forced to [[OutlivingOnesOffspring watch their children die as they inevitably outlive them all]].

In a strictly biological sense this trope is fairly logical. Without death, an immortal population would constantly grow and eventually crowd themselves out and deplete their resources. As such, childbirth isn't really a necessity for such a species, since the members rarely need replacement. The above formula can (loosely) apply to any given species.

This trope includes extremely LongLived characters and species with low birth rates, as they fit on the sliding scale properly. The most common example of this is elves; Tolkienesque elves generally are TheAgeless and can have children; their population is mitigated by a low birth rate (a typical elf couple can live together for several thousand years and produce only one or two children in all that time), the occasional violent death, and the tendency for older elves to [[PutOnABus journey across the sea to a mystical land, never to be seen again]].

Related to CreativeSterility; this is a focus on sexual reproduction. It can result in a DyingRace if the immortals can still be killed.



[[folder:Anime and Manga]]
* In ''Manga/FullmetalAlchemist'',
** homunculi, creatures created by alchemy, are stated as unable to reproduce. They exist outside of any ecosystem.
** [[spoiler:Hohenheim]] is immortal and can reproduce, but this doesn't affect his children (in both the anime and manga, but for different reasons).
* Played straight in ''Anime/{{Mnemosyne}}'' until a last minute epilogue subversion: [[spoiler:Rin herself]] bears a child, proving that it is possible.
* In the ''{{Metroid}}'' manga it's mentioned that the Chozo are slowly becoming extinct because their lengthened lifespan also made them very infertile.
* ''Manga/MahouSenseiNegima'' averts ImmortalityBeginsAtTwenty, causing this problem for pre-pubescent immortals.
** The vampire Evangeline has been around for hundreds of years, and presumably never reproduced. Although this may have more to do with the fact that she's evil, uber powerful, and scary as hell, as well as the fact that she gained immortality when she was ten years old [[NotGrowingUpSucks and has been stuck that way since]].
** [[spoiler:Negi himself]], due to [[spoiler:his transformation into a demon through Magia Erebea]], will stop aging "soon". He might still grow up for a few years, or be stuck with the same fate as Evangeline. Setsuna quickly starts to think about how it will be practically impossible for him to father any children like that. According to the StealthSequel series ''Manga/UQHolder'' [[spoiler:Negi was indeed incapable of having children. Someone decided to try to "clone" him to ensure his powers would be passed on somehow, and Negi's "grandson" Touta Konoe apparently resulted from that program.]]
* In the BleachedUnderpants manga that ''Manga/{{Hellsing}}'' was based on, Proto-Alucard explains that he kills off vampires who Turn too many humans because if there were too many vampires, there wouldn't be enough (read: ''[[ApocalypseHow any]]'') humans left to feed on. He bring this up in Chapter 1 of the actual series as well
* ''Manga/PrincessResurrection'': This is specifically the reason for the Royals killing each other off. Since a fully mature Royal becomes a Phoenix who literally ''cannot die'', ThereCanBeOnlyOne to become one.
* The [[FillerVillain Bounts]] from ''Manga/{{Bleach}}'''s Bount arc were a group of immortal, [[OurVampiresAreDifferent soul sucking]] humans who could summon BondCreatures, but they were incapable of reproduction. The one Bount that did have the ability to reproduce was killed by her own people as part of some elaborate ritual to [[ItMakesSenseInContext summon an army of flying, soul-sucking insects]].
* In ''Manga/DanceInTheVampireBund'' it's discovered that the "True Blooded" vampires can, in addition to [[TheVirus turning those they feed on]] into theoretically weaker ones, reproduce sexually. Problem is that females can give birth once and they apparently reach adulthood very slowly. Bigger problem is that [[spoiler:Dukes Ivanovic, Li, and Rozenmann apparently killed off the other 97 dukes [[StupidEvil and their families]] ''then'' slaughtered the whole Royal House of Tepes [[LastOfHisKind save for the young Princess Mina]] (who is under obligation to produce a True Blooded heir).]]
* Huey Laforet in ''LightNovel/{{Baccano}}'' procreated after becoming immortal [[ForScience just to see if this applied]]. His daughter doesn't inherit his immortality.
* The Juraians in ''Anime/TenchiMuyo'' have vast lifespans (one prominent member of the royal family is over 5,000 years old; she looks 35-40, tops), but their birth rates seem to be quite low. The Juraian emperor, for example, has been married to two women (at the same time) for over 700 years, and only had 3 children between them. His mother-in-law (the above-mentioned 5,000 year old Juraian) has only one biological daughter; while she's raised several other children, they were all adopted.
* In ''Manga/JoJosBizarreAdventure'' it is mentioned that the longer a species life span is, the less they reproduce. The pillar men were a long lived species outnumbered by the short lived humans, and when the BigBad Cars becomes the UltimateLifeForm, it is mentioned that he can no longer reproduce and doesn't need to, as he will never die.
-->''Sex = Useless''
* In ''LightNovel/SundayWithoutGod'', when people lost the ability to die due to God abandoning the world, they also lost the ability to give birth. As pointed out in-series, this makes Ai's existence even more perplexing, as she was born three years ''after'' God had abandoned the world.
* Pure-Blooded Devils in ''LightNovel/HighSchoolDXD'' are implied to have 10,000 year lifespans, and proportionately low fertility. After the GreatOffscreenWar caused a severe depopulation, with the [[ArsGoetia 72]] former great houses being reduced to ''three'' and remnants, this has become a serious problem. As of the start of the series, even high-ranking devils of the remaining noble houses are recruiting from humans they personally reincarnate, just to get their numbers back up and stabilize the population. Things have gotten so desperate for the devils that it's stated point-blank (in the novels, at least) that FantasticRacism has been ''marginalized'' by how dire the situation is, and even the proudest pure-blooded houses consider blood purity secondary to just surviving. The few who strictly stick to creating pure-blooded peerages are considered shortsighted and selfish by most of the population.
* In ''Manga/{{Toriko}}'', the Heracs are nearly immortal thanks to their extremely powerful HealingFactor. They also have very low birth rates. The Herac species is [[DyingRace in decline]] because they need "AIR" to reach maturity, and the Nitros have been harvesting "AIR" before the Heracs can reach it for a long time. In the present, the only Herac that can reproduce is the Horse King itself.
* Near the end of ''Manga/SoulEater'', it's revealed that [[spoiler:while [[TheGrimReaper Lord Death]] is immortal and was [[TrulySingleParent able to have a child]], that child unlocking his full power will cause the previous incarnation of death to die.]] [[DumbassHasAPoint Excalibur even points out]] that they can't just have immortals running all over everywhere.
* In ''Manga/DeathNote'', there is a rule stipulating that {{Shinigami}} are not to reproduce or have sex with either other Shinigami or with humans. Even if they wanted to do it, they wouldn't be able to, because [[NoBiologicalSex they lack the necessary "equipment."]] [[note]] and even if they had the right stuff, they might not be able to produce viable {{Half Human Hybrid}}s anyway. [[/note]]

* In the ''{{Wildstorm}}'' universe, the effectively immortal Kherubim suffer from an abysmally low birth-rate. Subverted in that it seems they can breed with humans more prolifically than they can with their own kind.
* Most elves of ''ComicBook/ElfQuest'' can only breed after a "recognition" (which is basically the instincts or [[WordofGod 'lizard brain']] of two elves deciding the two are genetically very compatible, and forcing them to conceive a child). One of the stories set before the Original Quest mentions that the tribe's [[HealingHands Healer]] tried, and was in one case successful, to break that limitation, because there were worries the tribe was too small. And later on [[spoiler:Leetah managed to induce Recognition for Nightfall and Redlance.]]
** One tribe of elves had no children for ''millennia'', partly because of stagnation (they were hiding from the world in a "fortress" and would not outgrow it). On the flip side, the Wolfriders have wolf blood, which may make them more fertile; a past chief, Two-Spear, was born to his father's lifemate, not his Recognized mate.
* Being a OneGenderRace, the Amazons of ''WonderWoman'' in Creator/GailSimone's run suffer from this, being reincarnated from women who were killed by men, including many mothers. They make "Whittle Babies" out of wood to keep themselves occupied, and until Diana was created by the Gods at Hippolyta's demand there were no children born on the island. A group of Amazons turned evil primarily because they were jealous that Hippolyta was given a daughter while they remained childless.
* After a {{retcon}}, ComicBook/TheEternals are completely infertile with each other, since they are NighInvulnerable, simply regenerate when you do hurt them, and are eternally young. Several of them have sired completely normal baseline human offspring with mortal lovers/spouses over the centuries, but this presents [[MayflyDecemberRomance other problems]]. Originally, the Eternals could and did procreate, albeit very rarely and many Eternals were noted as being the children of other Eternals and born long after the Celestials created their race.

[[folder:Fan Works]]
* Justified by a similar lack of desire in ''UndocumentedFeatures''. Humans who have taken the Detian treatment can have children. It's just that the current crop of Detians haven't had very many. For instance, Gryphon has been alive for over 400 years, but only started having children in the last couple decades.
* In the Franchise/MarvelCinematicUniverse fandom, this is a frequently-used fanon for [[Film/{{Thor}} Asgardians.]]
** ''Fanfic/ChildOfTheStorm'' suggests this, though it also suggests that Asgardians are significantly more fecund with human men and women.
* In FanFic/RainbowDoubleDashsLunaverse, alicorns are incapable of reproduction. There are only two known cases of alicorns producing offspring. The first involved six alicorns [[AllThereInTheManual in the deep past of the series]] who gave up their immortality to bring forth the first ponies. The second was the birth of Cadence, daughter of Princess Luna, as the result of a unique confluence of magical forces.

* In ''Film/{{Highlander}}'' and its various spin offs, the immortals cannot have children. If you believe [[Film/HighlanderIITheQuickening the second movie]], it's because they're [[HumanAliens actually from another planet]]. In the later films (but not in [[Series/{{Highlander}} the TV series]]), Immortals are capable of reproducing until they die for the first time. In [[Film/HighlanderIIITheSorcerer the third movie]] Connor has adopted a kid so he could have a son. This is also a plot point in [[Film/HighlanderEndgame the fourth]] and [[Film/HighlanderTheSource fifth]] movies.
* ''Film/TheManFromEarth'' fathered many children during his looooong life, but since he is forced to leave his families after a few years, nothing is known about their immortality, apart from one, and he is most certainly mortal.
* In ''Film/InTime'' people can reproduce freely, but to stay alive past the age of 25 you must work to obtain time, which also functions as currency. The practical effect of this is that only the rich are immortal, while the average lifespan is, if anything, far lower than normal thanks to the poor being [[KillThePoor worked to death by the system]] to control the population.
* In the ''Film/{{Underworld}}'' films, the immortal father of the vampire and lycan bloodlines seems to have stopped reproducing after his original three sons. At least, there's no indication that any other Corvinus bloodline existed for Lucien's agents to hunt down.
** Of course, considering that Alexander Corvinus has spent much of his immortal life "cleaning up" after vampires and lycans, keeping the existence of immortals secret, it's also possible he could have had other children in secret. Given how old he is, it could very well be that a good number of people are his descendants and don't know it (it's also made clear that not every descendant carries an inactive form of the immortality virus).
** Also, the Vampire Elder Viktor seems to have only reproduced once. There doesn't seem to be any reason for it other than the fact that, being immortal, he doesn't really have to worry about a silly think like an heir.

[[folder:Folklore and Mythology]]
* While the Greek gods certainly could mate with mortals, the demigod children were, themselves, mortal. A few favored ones like Herakles and Dionysus were later granted full godhood. The gods had kids among themselves less frequently. However, some of the elder gods, e. g. earth-goddess Gaia and some of the Titans, had plenty of children with each other. For instance the Titans Okeanos (Oceanus) and Thetys had 3000 daughters (river nymphs called the Oceanids) and a similar number of sons, the gods of all the rivers. One of the Oceanids, Doris, had 50 daughters by the sea-god Nereus.
* Averted in Literature/TheBible. Before The Flood, people could live centuries, and were stated to have children, some of them had lots of them. [[NotASubversion But that is not]] [[NotQuiteForever immortal]]. After the resurrection, Jesus states people will not marry anymore, therefore implying having children will be ended too, although they live forever.

* The Tucks from Natalie Babbitt's ''Literature/TuckEverlasting'' cannot change; they don't age, they don't die. Mrs. Tuck was past childbearing age when she drank from the spring, so it isn't an issue for the elder Tucks. However, the eldest Tuck son got married in the years after they drank from the spring and before they realized its effects; he had children, but his wife eventually thought he'd made a DealWithTheDevil and left him.
* Brought up in one of Joanne Bertin's ''The Last Dragonlord''. Dragonlords, the people who [[VoluntaryShapeshifting shapeshift]] between [[OurDragonsAreDifferent dragons]] and humans, have exceedingly long lifespans; as of the first book, the youngest is [[ReallySevenHundredYearsOld really six hundred years old]], still looks the same, and is still called "little one." They cannot have children with ordinary humans, and while that does not apply between Dragonlords, they voluntarily do not have children, since when they do reproduce their offspring are very nearly always human. The same Dragonlords who enjoy their human friends and grieve and let go when they age and die have a lot more trouble with it when it's their own children.
* In Creator/CJCherryh's ''Literature/{{Cyteen}}'', it is mentioned in passing that rejuvenation drugs have a side effect of making the user sterile.
* In ''Literature/GuildHunter'':
** [[OurVampiresAreDifferent Vampires]] over 200-years-old cannot have children.
** [[OurAngelsAreDifferent Angels]] have a ''very'' low birth rate, with sometimes ''decades'' between two angelic birth ''on the planet''.
* In Creator/MercedesLackey's [[UrbanFantasy Urban Fantasies]] and [[HistoricalFantasy Historical Fantasies]], the immortal [[OurElvesAreBetter sidhe]] can reproduce, but it happens extremely infrequently. As a result, children are treasured by both the Unseighlie and Seighlie Sidhe, although only the Seighlie expand this love to human children and try to save them from unpleasant fates.
** For the elves in Literature/TheObsidianTrilogy, children are also very rare and precious.
* Vampires from Meyers's ''Literature/{{Twilight}}'' were believed to be infertile, but it turns out that that only applies to the females. So the guys can still get it on with a human girl, but it's incredibly dangerous for the human woman.
** The same for wolves (though they're really only immortal so long as they shape shift). While there's only been one female wolf, she appears to have become menopausal after she became a wolf. The males can all still have children, a fact which is publicly known because of imprinting.
* A similar situation holds for the werewolves in Patricia Briggs's ''Literature/MercyThompson'' novels. The werewolves don't age (and if they were old when they were turned, they'll revert to looking adult, but permanently young and fit). Male werewolves can have children with ordinary women, but they'll be born mortal, and there's a high risk of miscarriage. Female werewolves can get pregnant, but inevitably miscarry when they change, which they must do at full moon. The only exception is Charles, the son of the Marrok, who is the offspring of two werewolves and was born one; his Native American mother used magic to hold off the change, but the effort depleted her strength and she died in childbirth. It's often a plot point that older werewolves often become unstable because they have outlived too many partners and children - in the Briggs 'verse it's dangerous to try to become a werewolf, as you have to be savaged to the point of death and not many survive the process, so they can't automatically turn their wives and children.
** Vampires in Briggs's 'verse seem not to reproduce in the usual way as they're not so much immortal as undead; they're literally dead during the day. They remain the same age as when they were turned. However, many of them assume a parental responsibility for new vampires that they have turned, and a vampire seethe acts very much like a big dysfunctional mafia family.
** Fae, on the other hand, can have children with mortals or with each other, and how "immortal" the children are seems to vary. There are lots of different kinds of fae and not very many of them in total.
* Used in Creator/TerryPratchett's ''Literature/{{Strata}}'', in which the universal currency is a life-extension treatment. One of the main characters, who is several centuries old, wonders what life would have been like had she been a "short-lifer" and thus able to have children.
* Inverted in ''Literature/DoraWilkSeries'', where nigh-immortal [[OurAngelsAreDifferent angels]] are ''insanely'' fertile, to the point where any sexual encounter, even with contraceptives, is nearly sure to result in woman getting pregnant.
* In Mickey Zucker Reichert's ''[[Literature/TheLastOfTheRenshai The Renshai Trilogy]]'' and its sequel ''The Renshai Chronicles'', it's remarked that the Norse Gods are ''almost'' completely infertile, and that many of them had a human parent. In the second trilogy, the life cycle of Elves becomes an important plot point: a new elven child can only be born if one of the currently existing elves dies (freeing their soul for {{reincarnation}}), so the Elven population can never grow beyond its current numbers. Furthermore, the elf needs to have died of natural causes - any violent death ''permanently'' reduces the maximum elven population.
** [[spoiler:There's a [[HalfHumanHybrid way around]] that limitation.]]
* There is a cultural mandate against reproduction by immortals in ''Jitterbug Perfume'' by Creator/TomRobbins.
* Averted in Creator/JRRTolkien's legendarium, as elves live forever but are perfectly capable of having children. They simply don't choose to do so very often; by the time of ''Literature/TheLordOfTheRings'', elves are near the end of a very long-term emigration, sailing away from Middle-Earth when they've grown weary of it, so overpopulation isn't a problem. In the stories set in the earliest time periods, though, there are frequently several generations of a single family living and ruling together, making a mental picture far more difficult than the two-generation Hugo Weaving/Liv Tyler pair in the films! There is also the implication that having children can be very spiritually draining for elves, restricting them from having too many. One elf was so diminished by giving birth that she essentially lost the will to live. The endless lives of elves also means that after a relatively short time, sex becomes boring to them. In his notes at one point, Tolkien indicated that elves do not have children after a certain age. (So, menopause?) Also, Fëanor and Nerdanel had the most children that any elven couple ever had, whereas seven children would be, if anything, low for most fertile human couples if they both lived through the women's child-bearing years in most eras.
** The ''Website/{{Cracked}}'' article [[http://www.cracked.com/article_18475_6-horrifying-implications-awesome-fantasy-movie-universes.html 6 Horrifying Implications of Awesome Fantasy Movie Universes]] discusses this: "no one in the Elfish kingdom is getting any, anywhere."
** Also averted with hobbits, who often have large families despite living longer than humans.
** But played straight with Ents, who live nearly forever but are all male and thus can't reproduce. Presumably wherever the Entwives are they have the opposite problem.
** Meanwhile (in the final version of the mythology) the even [[TheOlderImmortal Older Immortal]] Valar and Maiar don't reproduce at all.
* Creator/RogerZelazny's ''Literature/TheChroniclesOfAmber'' series: as the books themselves comment on, the immortal lords of multiverse have been around for millennia, but are not particularly fertile: the first book is ''Nine Princes In Amber'', not ''Nine Hundred Thousand Princes In Amber''. There is reference to several older princes who died "For the good of Amber" though.
* The immortals from ''Literature/TheCompanyNovels'', though [[spoiler: Mendoza manages to have children later on in the series. Very, very weirdly.]]
* In Creator/PoulAnderson's ''The Boat of Million Years'', the immortals are perfectly capable of reproducing. Unfortunately, the children are never immortal, even when both parents are.
* Completely ignored in Creator/RobertAHeinlein's ''Literature/TimeEnoughForLove.'' Many near-immortals live throughout the galaxy and reproduce like bunny rabbits, even if they're 20 centuries old. Their children may also be effectively immortal, depending on what genes they picked up and whether they have access to a rejuvenation clinic. They solve the overpopulation problem by continually colonizing new planets. Justified as reproduction was the entire ''point'' of the Howard Families. They were an experiment in human longevity that worked spectacularly well.
** It is worth noting that Tellus Secundus, the planet where the story begins, has an unusually high population of near-immortal "Howards" and in consequence has instigated population controls. The planet's chief executive mentions to Lazarus Long that he'll grant an exception to any woman Lazarus feels like having a child with. Lazarus himself is a special case as, being over two thousand years old and born at the start of the Howard experiment, he can claim over 80 percent of the galactic population and over 99 percent of Howards as his descendants to some degree or another.
* Sort of the case in the universe of the novels ''Literature/AmericanGods'' and ''Literature/AnansiBoys'' with two notable exceptions. In the former, Wednesday (Odin) tells Shadow that people like him generally "shoot blanks" [[spoiler: Shadow is Wednesday's son with a human woman, but rather than being a completely new god or simply human, he is an incarnation of the God Baldr]]. The book also informs the reader in ''Literature/AmericanGods'' that Mr. Nancy (Anansi) has a son, Charlie, who is the protagonist of ''Literature/AnansiBoys'' and is seemingly completely normal. [[spoiler: His brother, Spider, who was split from him, is basically a god, although the protagonist turns out to have RealityWarper powers]]. Charlie ends up having children, who seem to be human [[spoiler: while Spider appears to be infertile]]. Possibly on purpose, considering that the mother-in-law lives within spitting distance of them.
* Played straight ''so hard'' it hurts in ''Literature/{{Fragment}}''. When the protagonists discover the [[spoiler: mandatory sentient species that seems to be a part of any LostWorld or Alien planet, they discover that they are immortal ''because'' they don't have any babies in a combination of ClicheStorm and YouFailBiologyForever.]]
* In ''Three of Heart, One of Blood'', the Legacies are incapable of breeding, though the [[UnusualEuphemism systems]] still work. This is a fact that [[ReallyGetsAround Doryn]] uses and exploits. A lot.
* In the sci-fi ''The Declaration'' by Gemma Malloy, immortality has been made possible. Unfortunately, nobody who "opts-in" is allowed to have children because of this. Any children, or "surpluses," born to people who opt in are sent to [[OrphanageOfFear group homes]] and taught that they are worthless beings that do not deserve to exist.
* Fairies in ''Literature/ArtemisFowl'' (who are not immortal but very long-lived) can only have one child every twenty years; humanity's faster reproduction is actually the main reason it was able to more-or-less take the world from them.
* Witches in Phillip Pullman's ''Literature/HisDarkMaterials'' trilogy live roughly a thousand years. They take human men for lovers and bear children; if the children are girls, they're witches and if boys, human and short-lived. Presumably, they don't have children especially often. One character suggests that a witch dies when her heart is so broken from watching her lovers and sons grow old and die that she can't go on.
* Straightforwardly stated in C.S. Friedman's ''Literature/TheMadnessSeason.'' The vampires of that book are only fertile when they subsist on a diet of ''willingly provided'' human blood. This is explained in-text as an evolutionary mechanism to keep them from reproducing in an environment that isn't willing to support new vampires.
** The Marra, as well, are subject to this. Energy beings who are not able to die but can also not create new Marra (or, if they can, they have [[TheFogOfAges forgotten how]])
* Literature/TheCulture generally discourages having more than a few children but no one stops those who wants dozens. Given that they have unlimited resources it's not really a problem.
* Averted in Wen Spencer's "Literature/{{Tinker}}" series. The Oni are immortal and breed like mice. Famines are common in the Oni's overpopulated world. The Elves on the other hand are just as fertile as humans but don't feel the need to have as many children since they are immortal. The population of Elfland has dropped by 50% over the last two thousand years due to war, accidental death, and suicide.
* Unicorns in ''Literature/TheLastUnicorn'' (immortal but can be killed) live solitary lives in separate forests and mate very rarely.
* In Aleksandr Zarevin's ''Lonely Gods of the Universe'', the HumanAliens from the planet Oll arrive to Earth [[AncientAstronauts in distant past]], escaping from a power-hungry official. They plant some seeds they bring with them to grow food, and the seeds of a salad plant known as ambrosia grow practically overnight. After eating a salad made from ambrosia, they suddenly fall ill and wake up young and immortal. Somehow, an alien plant has acquired entirely new properties on Earth. They make a few locals immortal as well and establish themselves as gods on the island. While the females who become immortal are incapable of conceiving a child, this is absolutely not the case for any immortal male who sleeps with a human woman. That is, in fact, the cause of the many hair colors modern humans have. The original humans all had dark hair, while the Olympians (yes, [[Myth/GreekMythology those Olympians]]; they also call their island {{Atlantis}} after Atl, their home country on Oll) are all redheads. Immortality can only be achieved through consuming a sufficient quantity of ambrosia, which withered and died soon after blooming.
** The Ollans have managed to dry and preserve some ambrosia leaves. One of them is awakened by a Russian man after centuries in stasis. In return, she gives him a full dose. However, he decides to only take half of it and keep the other half for later. The half only heals his grave wounds and extends his life but doesn't turn him young or stop his aging. Later, he gives the other half to the protagonist's friend, who has lost a leg during the Soviet invasion of Afghanistan. The leg grows back overnight.
* In ''Literature/TheMoteInGodsEye'' series, the Moties ''invert'' this - if they don't have children, they die young and horribly. Oh, and the most likable group, the ones who learn English and talk to the humans of the series? They're sterile hybrids. They die after 25 years or so.
* In L. Jagi Lamplighter's ''Literature/ProsperosDaughter'' trilogy, since the immortality comes from an external source, they are fertile and most have had dozens of children. But the source is not extended to the children or spouses, and so some swore off it.
* Creator/KatherineKerr's ''Literature/{{Deverry}} series'':
** The Elves of usually live around 500 years, looking young until the last year or two of this, but have very few children during this time. Dallandra discusses the low elven birth rate with Cal and some other elves. It's hypothesized it's not just the length of their lives that restrict their birth rate, it's that part of their diet is meat, and meat-eating animals generally have a comparatively low birth rate. She also compares having children with humans as trading in some of their race's lifespan to have more children.
** Dwarves are also very long lived. Otho lives at ''least'' 400 years. Combined with their legendary stubbornness, it makes it very hard for them to let go of grudges.
* In the [[Literature/TheWitcher Witcher]] cycle, the Elves breed much more slowly than humans, because their women ovulate once in a couple of years (or even tens of years). Not to mention that after a hundred or so years, the sex gets boring. It's also mentioned they're only fertile at young age, but as later in the books a girl is bred with an elf over 500, it's probably only the women.
* In Creator/MikhailAkhmanov's ''Literature/ArrivalsFromTheDark'' books, Paul Richard Corcoran, being a HalfHumanHybrid, and his descendants have unnaturaly long lifespans (150-200 years). However, this also means they are highly unlikely to have children until they are well in their 40s or even 50s. This could indicate a slower rate of maturity.
** However, once able to have children, they usually have at least 2. One is noted to have 3 children of her own and then adopting 3 more (keeping a promise she makes at one point).
** One of the advantages the humans have over the Faata is their numbers and reproductive ability. Despite centuries of genetic engineering, the Faata still haven't figured out how to grow their race at a rate even approaching that of the humans. It also doesn't help that they deliberately engineer their lower castes to have a lifespan measuring only a few years, further reducing their population growth, despite the fact that they have a whole caste of breeders who are artificially inseminated and whose gestation is accelerated to a matter of weeks.
** This also applies to the [[VoluntaryShapeshifting Metamorphs]], whose lifespans are measured in millennia. Being a OneGenderRace, they reproduce by having several individuals fertilize one of them, which starts the budding process. It's mentioned by the Exile that his parent may or may not have another child, as births are a very rare occurrence for them.
** Completely averted in Akhmanov's ''Literature/CaptainFrenchOrTheQuestForParadise'', where humanity has discovered a cure for aging (called Cellular Regeneration, or CR). This doesn't stop people from having kids in the least, and many colonies have to impose PopulationControl. In fact, the titular character, being quite possibly the oldest human alive (being born in pre-CR days on Earth), has hundreds of thousands of children, although he explains that he didn't technically father any of them save one (his first daughter with his first wife), as they're all the result of artificial insemination with his sperm donated on many planets. However, this trope is, technically, preserved in that the CR treatment is not passed down to children and must be reapplied to everyone once they reach the age they want to be "frozen" in (most choose early 20s, although some prefer ealy 30s).
* Averted in ''Literature/TheDresdenFiles''. Wizards and other powerful magic users are very long-lived (they can be killed, but left to their own devices and otherwise unmolested, they'll go on for centuries), and they can reproduce. All seven Carpenter children are the product of at least a sorcerer-level talent and [[spoiler: Maggie Dresden is the unexpected daughter of Harry (a full-blown member/wizard of the White Council)]]. Harry's mother [[spoiler:also had another son a mere five years before Harry.]]
** [[spoiler:Harry also managed to give psychic-birth to a spirit of intellect "fathered" by the psychic coppy of the (female) Fallen Angel Lasciel]], although this isn't exactly a normal situation.
** However, the descendants of wizards/sorcerors are rarely gifted, meaning their lifespan is that of a mortal.
*** [[spoiler:Of the seven children born to Charity Carpenter, only Molly has shown any magical skill (although she has enough to be considered a true wizard)]].
*** [[spoiler:Thomas Raith]] is never shown to have any magical ability, although he [[spoiler:is a White Court vampire, negating his mortality]].
*** Anastasia Luccio (born sometime in the 1800s) laments the fact that she is now a many times great-ancestor, observing her family from afar for the rare magical talents. Senior Council member Martha Liberty is in a similar situation, although she lives with her family.
*** On the other hand, Harry's mother (a wizard herself) [[spoiler:was the only child of the incredibly powerful Ebenezar [=McCoy=]]], while [[spoiler:Maggie Dresden is expected to be powerfully gifted herself, meaning that wizardry bred true in at least four successive generations of this family]].
** The ''truly'' immortal [[TheFairFolk Sidhe]] are apparently only able to have children with mortals. The child will be born a changeling, and can choose whether to become fully human or fully Sidhe later in life. Since humans have free will and Sidhe don't, it can be a tough choice. Changelings are effectively immortal till this choice is made. While it is unknown exactly how changelings are, four born in modern times are seen in ''Summer Knight'', suggesting that the numbers could be relatively high.
** Averted again in the vampires of the White Court, who are functionally succubi/incubi. They breed relatively often for immortals. There are at least five Raith children in the main household, [[spoiler:and the patriarch of this family is known to have killed many of his sons]]. White Court vampires ''can'' avoid activation by having their first sexual encounter with someone they love, which essentially kills the demon inside them and renders them mortal. However, this is an uncommon occurrence.
* Literature/GeorginaKincaid, succubus, is unable to bear children since she became a succubus.
* In the Literature/TideLords Tetrology, the immortals cannot interbreed with each other (The union of an immortal egg and an immortal sperm would become immortal at age -9 months and thus never come to term), but they can and frequently have interbred with mortals (There are four entire ''species'' who are descended entirely from the mortal offspring of immortals). Said children are always born mortal, but [[spoiler: those children whose heritage makes them more than 50% immortal by genetics (Such as an immortal father and one or more immortal ancestors in the mother's line) can potentially ''become'' immortal]].
* Goes beyond this with the "glorifieds" in the Literature/LeftBehind book ''Kingdom Come'', since they won't even have the desire for sexual intercourse (because there is neither marriage in Heaven, nor any desire to sin, and extramarital sex is sinful).
* Averted in Creator/IsaacAsimov's story ''The Last Question''. After the human species has perfected immortality, the population is doubling every ten years. Even with intergalactic travel possible, there are concerns about having enough galaxies to fit everyone.
* The [[OurDragonsAreDifferent Kantri]] of ''Literature/TalesOfKolmar'' can live around two thousand years and are considered mature at two hundred fifty. About two hundred of them fled to the Dragon's Isle five thousand years ago and never increased their numbers. One observes with frustration that they ''should'' have increased, but the species seems demoralized and getting more so. There are fewer mated pairs and even fewer births happening all the time. It's mentioned with great concern that there have been [[DyingRace only three births in the past eight hundred years]] - and the Kantri with their huge claws are helpless in the face of complications of birth. If a human hadn't stepped in and midwifed during ''Song In The Silence'', [[DeathByChildbirth the first birth in three hundred years would have ended tragically]]. Also, Kantri only feel the desire to have sex a dozen or so times in their long lives, and the act is difficult and painful, not fun. Mated pairs enjoy 'joining souls', but this gets no one pregnant.
* Vampires and werewolves in ''Literature/TheParasolProtectorate'' cannot sire/bear children after their transformation. Understandable, since Step One in either transformation is "die". [[spoiler:With one exception; a supernatural (vampire or werewolf) and a preternatural such as Alexia ''can'' produce a child. But this is so rare that no one can confirm this until well into Alexia's pregnancy.]]
* The [[DifferentlyPoweredIndividual Others]] in Creator/SergeyLukyanenko's ''Literature/NightWatch'' books are fully capable of reproduction, but their children have just as much chance of being an Other as a child of two {{Muggle}}s (i.e. very slim). This is why many Others avoid having children, so that they don't have to watch them grow old and die. The Others aren't, technically, immortal, but even the weakest of them can enjoy several centuries of life. The most powerful ones tend to be thousands of years old and not look it. The vampires and werewolves are the exception, as they're able to "initiate" (i.e. bite) their children to turn them. However, vampires and werewolves are the lowers rungs of the Dark Others and are viewed at with little more than disdain. The Light ones see them as nothing more than beasts, while the higher Dark ones consider them cannon fodder. Additionally, they can only feed on humans with a license granted by the Night Watch. Doing so without one is punishable by death.
** Additionally, vampires can only have one child after being turned, at which point their reproductive ability disappears. Nothing of the sort is mentioned for werewolves, but then the author can't seem to decide if they're undead or not.
* According to prot[sic] in the ''Literature/{{K-PAX}}'' novels, since the [=K-PAX=]ian lifespan is over a thousand years, combined with their unappealing mating process(which involves profound pain, nausea and a bad smell), there's no problem with either under OR overpopulation.
* Amy Thomson said in [[http://io9.com/355206/amy-thomson-gives-good-alien an interview]] that "I believe that societies whose individuals have immensely long lifespans, must either have very few young, resulting in a stagnant, inflexible, rigid culture, or else they must place cultural limits on lifespan in order to have the cultural renewal of a younger generation." She chose the latter, so while both the Tendu and the harsels in her books can theoretically live forever if not killed... they don't. Harsels choose to reproduce and die in the act of giving birth to hundreds of nonsentient harlings, which [[BizarreAlienReproduction chew their way out of their mother's flesh]]. Tendu spawn in huge numbers throughout their lives, but they ''eat'' their nonsentient young, or otherwise are not concerned by animals eating them. Most adult Tendu select one nonsentient subadult and cause it to metamorphose into an adult which is then cared for and taught, and choose to die soon after this child/apprentice is fully mature; there are a few individuals who choose not to die, and then they are culturally compelled to leave home forever and metamorphose again, becoming sort of wandering judges/problem solvers. This is portrayed as more frightening than death. It's mentioned that there was a time when they did things differently and the ecology was absolutely swamped with Tendu, and there weren't enough resources for everyone.
* Both averted and justified in the ''Literature/{{Discworld}}'' novel ''Carpe Jugulum''. Vampires are perfectly capable of reproducing, through both the bite and the normal way, but they seldom ''want'' to because it means more competition for food. Even worse, the vampire parents usually expect their offspring to [[NotAllowedToGrowUp remain their loving, obedient children for all eternity]]. This does not go over well with the kids.
* In Lynn Flewelling's ''Literature/{{Nightrunner}}'' series, the human wizards live up to 400 years but are also sterile (and most of them are celibate as well, apparently mostly for cultural reasons). This is actually a problem in the setting, as only humans with some degree of [[OurElvesAreDifferent aurenfaie]] blood can have magic powers and the Aurenfaie have been very isolationist for the last few centuries. So the number of wizards is slowly dwindling, and this is becoming a military disadvatage for the main culture in the story. The royal family, who have an Aurenfaie ancestor a few generations back, live about twice as long as pure humans and most of them can reproduce, though. On the other hand, they don't appear to have any magic talents. The Aurenfaie themselves live 300-400 years and are fertile (the family the reader learns most about had at least 4 children before the mother died) but despite occupying a limited territory, they don't appear to have any population problem. This may be because they don't allow a youngster to marry until he or she is well on their way to their 100th birthday, even though they develop a sex drive somewhere around the age of 20.
* In the short story [[http://www.gutenberg.org/files/21279/21279-h/21279-h.htm ''2 B R 0 2 B'']] by Kurt Vonnegut, medicine has conquered old age and death. The population numbers are kept under tight control to avoid resource overuse. This means you have to convince someone to volunteer to die in order to have children. The main character's wife is giving birth to triplets...
* In Creator/MCAHogarth's ''Literature/{{Paradox}}'' series the Eldritch live for over a thousand years, but due to complications with their genetic engineering and inbreeding their fertility rate is dropping. Jahir's mother was noteworthy for bearing two children.
* Humanity's TransHuman descendants in the ''Literature/GreatShip'' series rarely ever have more than one or two children (in normal circumstances) despite living for an [[TimeAbyss hundreds of thousands of years]]. Part of the low birth rate seems to be implied by parents having to [[PopulationControl pay for addition berths]] on the [[PlanetSpaceship Great Ship]]. However, their fertility is unchanged - Dream's mother in ''Eater-Of-Bone'' had several children; though all but Dream died from malnutrition due to the LostColony's near-total [[MetalPoorPlanet absence of metals and salts]] vital to their [[HyperactiveMetabolism augmented metabolism]].
* In the fourth book of the ''Literature/SpiritAnimals'' series, the heroes stumble across a town which has been drinking from a magic pool. The pool makes you immortal as long as you keep drinking (if you stop drinking, you die within a few years), but also renders you infertile.
* In ''Literature/{{Neogicia}}'', a character suspects this is the reason for which the imperial family doesn't share the LongevityTreatment that is being used on its own members. Also, thanks to that technology being something that started small and got better over time, the emperor is expected to produce a heir at some point just in case. Said emperor is currently more than a thousand year old, looks 35 (his father died around the same age looking like old man) and is still single despite the long line of candidates to be his wife.
* In ''Literature/TheLifeAndAdventuresOfSantaClaus,'' none of the immortals are allowed to reproduce, or even seem to have a concept of children--but the idea is so attractive that it prompts [[SupernaturallyYoungParent Nicele]], a nymph, to raise the [[DoorstopBaby foundling]] SantaClaus as her child.
* Creator/EdgarRiceBurroughs' ''Literature/{{Amtor}}'' series had the Vepajans, Venusian HumanAliens who consumed [[ImmortalityInducer an anti-aging serum]] that extended their lifespan and allowed them to live indefinitely. Half their women are also infertile, and the other half is allowed to breed a limited number of children to avoid overpopulation.
* ''Literature/ThisImmortal'' has the variety where the immortal, in this case Conrad Nomikos, ''can'' and ''does'' have offspring, but they only marginally benefit from that, living slightly longer than normal but not unsuly so, thus causing him to watch them die. Conrad, however, does not seem particularly fazed by that as [[LivingForeverIsNoBigDeal that's just how things are]].
* In ''Literature/{{Spin}}'', the Martians have a series of drugs that induce their "Fourth Age". It prolongs their life and greatly enhances their abilities, but in order to prevent overpopulation, the drugs also cause sterility.
* ''Literature/JourneyToChaos'': Elves zigzag this trope. The first time a female elf has sex she will become pregnant, no exceptions. After giving birth, she will be barren for a century or two and then be able to conceive again. Thus, the only siblings that can experience growing up ''as siblings'' are twins, triplets etc. If their population needs an emergency boost (such as after the Conversion War) then the males in the population can [[SexShifter sex-shift]] into females and carry a child to term.

[[folder:Live Action Television]]
* ''Series/StargateSG1''
** The Asgard are not capable of sexual reproduction; they lost the ability due to extensive genetic alteration. To achieve immortality, they upload clone bodies with their memories when their old bodies die. Eventually even this tactic fails.
** The normal life cycle of Goa'uld includes the spawning of new parasites by extremely rare slug-like queens, with Jaffa specially prepared to incubate the larvae; this almost always happens off-screen.
** Procreation between two Goa'uld ''hosts'' is forbidden. The resulting child is very dangerous; thus the practice is proscribed. Such a child, known as a Harcesis, would be born with all the genetic memories of the Goa'uld. Exactly why this would be a bad thing for the Goa'uld is never spelled out [[FridgeBrilliance but it's probably to prevent Goa'uld secrets from falling into the hands of enemies like the Tokra or the Asgard]].
** In the episode "[[http://stargate.wikia.com/wiki/2010_(episode) 2010]]" the Aschen weaponized this trope. After making contact with Earth they offered a treatment that would cure all diseases and drastically (though not infinitely) extend human lifetimes. After everybody on the planet got the treatment, SG-1 found out that it had a component not in the original formula; it caused sterility and would lead to the extinction of 90% of humanity. This was that civilization's way of taking over planets without a fight, just a bit of patience. Fortunately, the main characters were able to cook up some time travel gimmick to warn their past selves to not allow this to happen.
* ''Series/BuffyTheVampireSlayer'': With one important exception, the immortal vampires in the Franchise/{{Buffyverse}} cannot create natural children. Even in that one exception, the vampire mother could not bring the child to term the normal way, and the child was mortal anyway.
** Mortal in the age-and-eventually-die way, but he had all the strength, speed, and super senses of a powerful vampire with none of the weaknesses.
* In ''Series/NewAmsterdam'', John Amsterdam has had several children, who, unlike him, are mortal. One of these children, Omar, looks older than John himself, and knows about John's immortality.
** One episode shows that John keeps records of his descendants, so he can keep track of them and [[IncestIsRelative avoid dating female descendants]].
** Both Omar and an elderly female descendant shown in a flashback where John is secretly dating Omar's mother are upset when John tells them that he still hasn't found his soulmate. Of course, what John means is the one woman who would cause his "curse" of immortality to end.
* Captain Jack Harkness, from ''Series/{{Torchwood}}'', is another aversion. He's immortal, but can have children. The children, again, are not immortal, thereby preserving the intent of the Clause.
** Given that he's [[AnythingThatMoves Jack Harkness]], he should have lots and lots of children and grandchildren running around if that was the case, not just one family. It makes more sense that the Time Agency routinely sterilised its agents (Would you let people like Jack or John run around in eras without reliable birth control and potentially father their own ancestors?) and that the daughter in season 3 was the result of a 1960s orgy. It's not like Jack is the jealous type who'd refuse to raise the kid as his.
** The fourth series, ''[[Series/TorchwoodMiracleDay Miracle Day]]'', is set to involve a thorough subversion of this trope; humanity mysteriously becomes immortal and one of the immediate problems is an impending overpopulation crisis.
*** Seems a bit fast though: if the average human lifespan on all of earth is say 50 years, than the population would grow with a staggering 2% a year. This trope only a problem in the long term. (Though in it's defense the show mostly shows us overpopulation in hospitals, which would happen far earlier than overpopulation of earth)
*** They also quickly state that humans still age normally. Nursing homes would end up being overpopulated fairly quickly too.
*** Abortion also becomes an issue (even more than in RealLife), when it's stated that an aborted fetus would probably still be alive but no longer able to grow outside the uterus.
* The Cylons from ''Series/{{Battlestar Galactica|2003}}'' are immortal due to their resurrection technology. They are also near-universally infertile, with only a single [[HalfHumanHybrid half-human]] child born to the entire race.
** One notable exception exists, but [[spoiler: did not survive to term]]
** [[spoiler: Inverted with the all-Cylon Thirteenth Tribe. The ancestors of the Final Five could reproduce, so they abandoned their resurrection technology.]]
* An episode of ''Series/TheTwilightZone1959'' features a movie actress who remained remarkably youthful despite starring in films from the Silent Age (this taking place in the 1960's). She was accompanied by an old woman who acted as a maid. [[spoiler: Turns out the actress is none other than Cleopatra, who regains her youth by draining the life force from other people. And the old woman? It's her mortal ''daughter''.]]
* Series/DoctorWho 's Time Lords live for millenia. Though the TV show never mentions it, this trope is fully in play in the Franchise/DoctorWhoExpandedUniverse: the ''whole species'' has been infertile for hundreds of thousands of years, and reproduces artificially through "Looms".
** The only reason they are infertile is because the original leader (who was overthrown as a result of a revolution), placed a curse on them that took thousands of years to remove. Odds are that they reproduce like normal humans do, but now have gotten so use to the looms that they stop sexually reproducing.
* In ''Series/BabylonFive'', Lorien mentions that his naturally-immortal species had a very low birthrate, "less than a handful each year". Since their immortality only made them ageless, not indestructible, their population was kept in check by injury or illness.
* A second season episode of ''{{Series/Spellbinder}}'' has the protagonists end up in a parallel world where, somewhere around Enlightenment, a deadly plague wiped out a large number of people and threatened to make humans extinct. A cure was found that, miraculously, also made them immortal. Unfortunately, they found out too late that this trope was in full effect. No one subjected to the cure (all survivors) can conceive. Thus, when the protagonists arrive, it's been over 200 years since the plague, and the world still looks like it's in the middle of 18th century with almost no progress having been made, except with animatronics, which are used to make child-like automatons that the immortals can pretend to be children. When a MadScientist finds out that the arrivals (a teenage girl and a 20-some man) are fertile, he kidnaps them, intent on using them to repopulate the world or at least provide ''some'' new people around.
* In ''Series/TheVampireDiaries'', vampires cannot procreate. This actually comes up when Elena wonders whether, supposing Katherine was her ancestor, she was part vampire. Damon shoots this down and says that if Katherine had any children, it was before she became a vampire.
* In ''Series/{{Forever}}'', Henry doesn't appear to have any children of his own, not for the lack of trying. He adopted Abe as a baby after finding him in Auschwitz after the [[WorldWarTwo war]]. In fact, Abe later finds out that they are, in fact, related, as Abe is descended from Henry's uncle.
* ''Series/ForeverKnight'': Vampires cannot have children of their own. This leads a 200-year old vampire lover of Nick to kill herself by committing SuicideBySunlight because she can't bring anything new to the world.

[[folder:Tabletop Games]]
* Most of the various immortal races in the TabletopGame/OldWorldOfDarkness are like this. Only the weakest 14th or 15th generation vampires in ''TabletopGame/VampireTheMasquerade'' can have children, who end up as [[{{Dhampyr}} dhampirs]], only extremely yang-imbalanced TabletopGame/KindredOfTheEast can have children (their version of dhampyrs), and that's made increasingly complicated by the fact that a female Kuei-Jin has to remain yang-imbalanced throughout the pregnancy, and demons from TabletopGame/DemonTheFallen might possess human bodies, but they lack the spark of life to create true progeny.
** The original mummies were sterile too. However, their successors, the mummies of ''TabletopGame/MummyTheResurrection'', are fertile, capable of having mortal children (justified, as the mummies' immortality is the result of the Spell of Life).
** It carries over into the [[TabletopGame/NewWorldOfDarkness new version]]; a [[TabletopGame/VampireTheRequiem vampire]] can only give birth to a [[{{Dhampyr}} Dampyr]] through the use of certain dark rituals and curses, and the [[TheFairFolk True Fae]] of ''TabletopGame/ChangelingTheLost'' are described as immortal, all-powerful, and utterly sterile. [[spoiler: That is, until you find out that the titular changelings risk ''becoming'' True Fae if they hit Wyrd 10 and Clarity 0 -- which means their abduction/MindRape was ''the reproductive cycle''.]]
* In ''TabletopGame/DungeonsAndDragons'', the lifespan of elves has decreased somewhat over the various editions (from a maximum of two thousand years for grey elves in 1st edition to a handful of centuries now); perhaps this is appropriate, considering that they've become more and more common in their game worlds, suggesting higher levels of procreation. Okay, fine, they're still supposed to be majestic, long-lived, and rare, but RuleOfCool sometimes dictates otherwise.
** They say now that Elves do reproduce, but it's a long pregnancy, and that they need to wait 5 years to get pregnant again.[[note]]The book, ''The Book of Erotic Fantasy'' had an explanation that elven pregnancies last a full ''two years'', which does a number on the mother's body as one would assume[[/note]]
** Another example is the 3.5 edition Elan, a race of psionically enhanced and modified humans who are functionally immortal. They can no longer procreate with humans due to their modifications (they are classified as [[HumanoidAbomination aberrations]], not humanoids), and the only way to make more Elans is by modifying an existing human with a mixture of psionics and [[SuperSerum an alchemical conversion process]].
** Completely averted with [[OurDragonsAreDifferent Dragons]], however, which are some of the longest-lived beings in D&D. The only issue with them is that after a certain point in their lives females stop being fertile, and mortality rate is relatively high amongst younger dragons, so they're not overrunning the world.
* ''TabletopGame/{{Warhammer 40000}}'':
** The fluff and lore about Space Marines and whether or not they can even sire children, much less raise them, is very vague and ill-defined, but given the massive physiological changes a baseline human goes through to become an Astartes, along with his psychological conditioning and the simple fact of Marines being created specifically as soldiers, it's ''very'' unlikely that any would have kids.
** The Eldar combine a low birth rate with a natural aversion towards any sort of extreme emotion (an Eldar having sex is practically begging to get his soul sucked out by Slaanesh), to the point where their population is likely just below sustainability levels.
** Played with by the Dark Eldar. They can indeed reproduce, but the majority of Dark Eldar are vat-grown clones (which serve as mooks in combat or spare bodies in experiments) which are only sub-par (allegedly) in combat skill but otherwise differ little from actual Dark Eldar. Dark Eldar literally feed on pain and uses this to extend their lifespans. Asdrubael Vect, Archon of the largest Dark Eldar Cabal, is currently the oldest living being in the universe, bar the Chaos Gods and Necrons. Having natural "True-born" children is a privilege reserved for the upper-echelons of Dark Eldar society.
** The Necrons gained immortality by being transformed into robots, which obviously presents a rather insurmountable obstacle to reproduction. In fact their (active) population is not particularly high, yet can war with other races with little issue because any "killed" Necrons are immediately teleported back to their base and repaired by automated systems.
** In early editions, the GodEmperor had fathered quite a few children in his 39,000 years. Known as the Sensei, they were also immortals with psychic powers, and were hunted down by the Inquisition either to make more psyk-out weapons or to sacrifice them to jump-start the Emperor.
* ''TabletopGame/{{Warhammer}}'':
** Invoked by [[JerkassGods Tzeentch]]. The ancient race of Dragon Ogres asked the Lord of Change for a boon, to make them immortal. He did, but also rendered them sterile. Most of the still-living Dragon Ogres consider this to be Tzeench's idea of a joke.
** The Slann, the rulers of the Lizardmen, do not seem to be able to die of old age (the oldest are old enough to remember the [[{{Precursors}} Old Ones]]), but there have been no new spawnings of Slann since the disappearance of the Old Ones some eight thousand years before the present day. None of the Lizardmen species in Warhammer breeds in a sexual manner, their eggs simply come into being in magical spawning pools deep in the Lustrian jungles - each new spawning occurring according to the (now much fragmented) plan of the Old Ones. But the Old Ones didn't plan on needing more than five generations of Slann, and there is nothing the Slann themselves can do to increase their numbers, so they are now a dying race, and the loss of even one is an incalculable blow (See Warhammer: Lizardmen (2013), p. 31).
** Elves can live for thousands of years, but produce so few children that they are slowly declining and dying out. Warhammer's Dwarfs live for hundreds of years, and seem to breed at far below replacement levels as well. Meanwhile short-lived humans breed at human-normal rates and the rat-like Skaven, the vast majority of whom never live past twenty, breed in huge numbers like the swarms of vermin they are.
** The Undead, including Vampires, are completely unable to reproduce. Except by raising more corpses with magic.
* ''TabletopGame/{{Spycraft}}'' has a setting, 'World on Fire'. One faction is the Eternals, which are ExactlyWhatItSaysOnTheTin. They can have children, but these are very very mundane.

[[folder:Video Games]]
* In ''VideoGame/{{Creatures}}'' games, there are many "immortal" third-party breeds; the majority of them are infertile by default, because immortal creatures capable of breeding would overpopulate the world pretty quick.
** But the Fast Ager Norns, who tend to evolve spontaneously in many C3/DS wolfing runs, avert this. Maturing within seconds, [[ExplosiveBreeder very fertile]], and immortal, they will easily max out your population no matter what population limit you choose. They're basically the cancer of the norn population.
* In the ''VideoGame/{{Fallout}}'' series, the two types of creature that are biologically immortal, Super Mutants and Ghouls, are both unable to reproduce. The former due to sterility as a side effect of FEV perceiving the 23 chromosomes in sex cells as "damaged" and "repairing" them by filling in the missing chromosomes, and the latter... radiation sterility and, well... rot?
** Van Buren would have had "born ghouls," children born into ghouldom. To Drs. Sebastian and Clark, the masterminds of the breeding program, the born ghouls represent the future of the ghoul "species."
* Averted in ''VideoGame/LostOdyssey'': the five immortals can and do have children, but their children, even when both parents are immortal are not themselves immortal, mainly for plot reasons. This prevents any potential overpopulation problems.
* ''Franchise/MassEffect''
** Initially averted with the krogan. They were a species of walking tanks that gave birth in litters of over a thousand, and are functionally immortal (it's not even clear if they ''can'' die of old age). However, while their DeathWorld homeworld kept their numbers in check, once they were colonizing more pastoral worlds, [[ExplosiveBreeder their population exploded in a single generation]]. To stop the Krogan Rebellions, the entire species was infected with a virus that devastates their birth rate (1 out of 1000 is live, the rest are stillborn). And even with the high mortality rate, they're still capable of maintaining a population equilibrium if not for the species wide fatalism that followed the Genophage (kind of hard to keep you chin up when your contemporaries annihilate a fundamental aspect of your biology and society).
*** Some parts of fandom describe the Genophage's results as BroughtDownToNormal, since even with that death rate the krogan still don't die of old age and still get a viable egg or two in the typical clutch.
*** Mordin states in ''MassEffect2'' that the salarians very carefully tailored the genophage (and later modified it when the krogan began to adapt) to replicate the pre-industrial krogan birth rate to give them a "natural" (low) population growth.
** The asari, who live for one thousand years, don't seem to have a problem with this trope though. They happily breed all they want to. On the other hand, in order to become pregnant, the asari has to be consciously trying to become pregnant. They can have sex all they want and only reproduce when they have a desire to. The asari, of course, are an entire race of [[GreenSkinnedSpaceBabe Blue Skinned Space Babes]], which probably rejiggers their place on the immortality vs. fertility continuum. Most of the time the asari don't choose to procreate before they pass their 300th birthday and become Matrons, and generally don't have that many children in their whole lifetime; nearly 1000-year old Matriarch Benezia only has one daughter, for example. Aethyta, who's as old, is implied to have had a good number, but then her father was a krogan.
* True Ancestors in ''{{Tsukihime}}'' are noted in [[AllThereInTheManual supplementary materials]] to have been rather on the decline. They did not even have enough children to replace the members they lost, so the birth of Arcueid itself was pretty big news even before people knew how powerful she was. Possibly tied to the fact that they were almost entirely all male.
* In VideoGame/GoldenSun II, the ancient lost civilization of Lemuria has a grand total of two children, both of whom comment on how lonely it is being surrounded by ancients. (Lemurians aren't strictly immortal, but they slow down their aging process to live many centuries.)
* Averted in ''VideoGame/DwarfFortress'', with interesting results. Elves mature and reproduce at the same rate as humans, but have no upper limit to their ages. This results in massive populations; they would have taken over the world by [[ZergRush sheer dint of numbers]] if it weren't for two weaknesses: they are poorly armed (having only wooden weapons and armor) and they are ''[[ImAHumanitarian cannibalistic maniacs]]'' who start wars over the way other species treat ''[[AnimalWrongsGroup plants]]'', [[ViciousCycle resulting in them warring with pretty much all of their neighbors]]. Battles with ''thousands'' of elves fighting (and losing to) less than a hundred dwarves are not uncommon.
* ''VideoGame/WorldOfWarcraft'' has the Draenei, who live for at least tens of thousands of years (and may be immortal), and [[WordOfGod very rarely have children]].
** Also, now that Night Elves are no longer immortal (their natural lifespan is still probably pretty long, but not infinite) they're starting to have kids more, as evidenced by some of their quotes.
* Played straight and Averted in [[VideoGame/TheSims The Sims 2]]. Zombies and Servo robots are immortal but cannot have children, while Vampires can reproduce, but any children born will be completely normal.
** In ''The Sims 3'' Vampires are no longer immortal (though they still live much longer then regular sims), and can have children at the same rate as ordinary Sims at least in theory although only half of their children with an ordinary Sim will be Vampires. Also, the Fairy Sims in the Supernatural expansion have the same lifespan as Vampires, and can likewise reproduce at the same rate as ordinary Sims. Both also age at the same rate as ordinary Sims until they reach adulthood.
* In ''VideoGame/RuneScape'', the Dragonkin are nearly immortal, living for thousands of years at least, but can still be killed, and can't reproduce. This has lead to them becoming very afraid of death.
** Justified for the Mahjarrat; creating children costs them massive amounts of their difficult to replenish divine LifeForce. This ultimately lead to the extinction of the other two tribes of their race as they were no longer receiving enough LifeForce from the CreatorGod that made them. Also, there's only one ([[HalfHumanHybrid pure]]) female still alive, and she's rejected all suitors.
** The [[OurVampiresAreDifferent vampyres]] avert this trope-- they're long-lived, prolific, and capable of converting members of other races into more vampyres. Consequently, they have a big overpopulation problem, and living prey in Morytania is increasingly scarce... and increasingly desperate.
** The elves live so long that one of them loses track of ''entire centuries'', but elf children can be seen prancing around Lletya and Prifddinas, so clearly fertility isn't a problem.
* The [[AllTrollsAreDifferent Trow]] in {{Creator/Bungie}}'s ''VideoGame/{{Myth}}'' series were created as an entire species by the god Nyx at the begining of the world. They have no natural causes of death, are eighteen feet tall, and have bodies that are as tough as stone. For many thousands of years they dominated the world, but entropy and a series of costly wars took its course, and now [[DyingRace there are only a few hundred Trow left, if that]]. The ones that remain tend to keep to themselves, but pray you never have to [[DemonicSpiders run into one on the battlefield]].
* A female dwarf in ''VideoGame/DivineDivinity'' mentions that she is pregnant, but she's only in her tenth month, so she's not showing any visible signs yet.
* In novels for ''VideoGame/StarCraft'', the [[NeglectfulPrecursors Xel'Naga]] were incredibly long-lived but couldn't reproduce. [[spoiler: Instead, they turned other races into more of them!]]
** Technically, what they tried to do was [[spoiler:create 2 races: one to have a "perfect form" and one to have a "perfect spirit". After millennia, the two would eventually join to evolve into the next cycle of the Xel'Naga. Unfortunately, someone threw a monkey wrench in the works]]. ''Legacy of the Void'' sheds more light on the situation. [[spoiler:The Xel'Naga don't specifically create or modify any race to become their successors. They simply wait until races with the proper qualifications (the purity of form and essence) find their way to them pass on the mantle of Xel'Naga to them. The term Xel'Naga doesn't describe a species -- it describes a ''duty''.]]
* In Aselia's ending for ''VisualNovel/EienNoAselia'' [[spoiler:both she and Yuuto are Eternals]] and have a child together. This is apparently completely unheard of and they're a bit nervous about how they're going to explain it.
* In ''Franchise/TheElderScrolls'', the Mer (Elven races) live considerably longer (how long is undisclosed), but have far fewer children. However, their chance of having children is higher if they have a non-elven lover, and the Bretons are an entire race of Mer/Human hybrids who eventually outbred both of their parent races in the region of High Rock.
** This is stated to have caused a major problem for the Falmer (Snow Elves) back in the First Era, since they did not breed as much as their neighbouring humans did. This caused peace to break down and the result was that the Falmer were driven to extinction or horribly mutated, [[spoiler:bar a few hundred individuals that did indeed survive]].
* In-game documents and supplemental materials for the ''VideoGame/{{Myst}}'' series reveal that the D'ni, whose lifespans could run into a fourth century, reproduced very slowly due to the narrow window (30 hours every 72 days) in which their women could conceive.
* In ''VideoGame/SonicAdventure'' and ''VideoGame/SonicAdventure2'''s Chao Gardens, Chaos Chao are immortal, but can no longer breed.
* In the ''Franchise/StarCraft'' universe, the Protoss are a very long-lived species; Artanis, at 262 Earth years old, is considered "young", while Matriarch Raszagal was 1,045 at the time of her [[MercyKill unnatural]] death. They are also stated to be "not a prolific people"; even before the events of the first game, the Protoss' population was steadily declining, as they were dying of old age faster than they could bear new children. The Fall of Aiur, with the resulting tremendous fatality count, worsened the situation.
** It doesn't help that the various Protoss tribes killed each other in droves during the Aeon of Strife, only stopping after Savassan (AKA Khas, "He Who Brings Order") used Khaydarin crystals to mentally unify the race.
* Janos Audron in ''VideoGame/LegacyOfKain'' says "Vampires are no longer born" implying that Vampire meant a race, and the curse that caused them bloodthirst and immortality also made them sterile. They tried to preserve their line by passing the curse onto humans.
* The Manaketes of ''Franchise/FireEmblem'' live for thousands of years, and depending on the setting either are almost all sterile or reproduce at a slower rate.
** ''[[VideoGame/FireEmblemAkaneia Mystery of the Emblem]]'' mentions that the event that caused dragons to assume Manakete form made them unable to give birth.
** ''[[VideoGame/FireEmblemElibe Binding Blade]]'' has dragons losing the war with humanity due to their inability to reproduce at humanity's rate, forcing them to rely on [[CloneArmy Artificial soldiers]].
** ''[[VideoGame/FireEmblemAwakening Awakening]]'' seems to ignore this despite being in the same canon as Archanea, as it features three Manaketes, all fertile, and absolutely no mention of the race's sterility either way.
* In the ''Franchise/{{Pokemon}}'' games, there are Pokémon which are known as "Legendary Pokémon" which have immense powers and mostly serve as deities in legends. Most of them may be immortal, and with a few exceptions, unable to produce more offspring. In the games themselves they're unable to breed (mostly so you can't produce more of them in-game).
* When you [[spoiler: end up in ancient Iconia]] in ''VideoGame/StarTrekOnline'' the (to all appearances immortal to age) Iconians mention that they ''do'' reproduce... very, ''very'' slowly. That there were twelve Iconians at the fall of Iconia and twelve Iconians at the beginning of the Iconian War, 200,000 years later, probably has something to do with what they turned themselves into in their quest for vengeance... [[spoiler: as well as the loss of the World Heart, their central repository of information on the universe and themselves]].
* Boss Monsters in ''VideoGame/{{Undertale}}'' [[TheAgeless do not age past maturity]] except when they have living children. [[OutlivingOnesOffspring If their child dies before their parent]], the parent ceases aging again.

[[folder:Web Original]]
* As a demonstration of why this trope is often necessary, the site ''Grudgematch'' had a [[http://www.grudge-match.com/History/bond-indy.shtml hilarious take on the disastrous consequences]] of James Bond winning immortality in the grudgematch: massive inbreeding due to James' libido.
* Elves in ''Literature/TalesOfMU'' are true immortals in terms of lifespan, and generally quite sexually potent as part of their being [[OurElvesAreBetter better than everybody]]. They keep their birth rate low by doing things that don't produce children.
* The alien race known as the Silent Ones in ''WebOriginal/OrionsArm'' use a treatment that completely halts aging but severely stunts the development of their larvae, so they keep small groups of mortals to replace the few immortals that die. However most Terragen (human-derived and/or created) sophonts are effectively immortal and decidedly ''not'' infertile, the population being in the quadrillions about 10500 years in the future.
* WordOfGod (pun intended) has this as being the demographic issue with the angels in ''Literature/TheSalvationWar'' -- "angelic females simply are not very fertile and the chance of conception is extremely low," so the reason for the war being fought on Earth is to put off or prevent any human incursion into Heaven. Whereas the daemons tended to be [[KillEmAll killed ''en masse'']] in generally horrible ways during the [[CurbStompBattle Curb-Stomp War]], their birth rate will allow them to eventually recover, whereas angels dying off in those numbers might actually cause them to go extinct.
** Although as of Chapter 83, it seems that the low birth rate of the angels was at least partially due to Yahwehh's obsession with controlling sex and sexuality and now that [[spoiler: he's been killed]] there's been a rash of pregnancies among the angels [[spoiler: including Maion]].
* [[http://writersworkshop.wikia.com/wiki/Controlling_Populations_of_Immortals Dissected (and arguably deconstructed)]] by the Writerium (and its successor the Writer's Workshop).
* [[http://www.newscientist.com/blogs/shortsharpscience/2009/03/why-vampires-would-have-a-popu.html This blog post]] hilariously suggested that romances like the one in ''Literature/{{Twilight}}'' ''prevent'' vampire from population problem.
* The eponymous Roleplay/AHDotComEternals can have children normally both with ephemerals and other eternals. The vast majority of these children are completely mortal though. The character of Gregorios, for example has had more than 160 children over the course of his lifetime, and only one other has proved to be an immortal so far.

[[folder:Web Comics]]
* ''WebComic/DanAndMabsFurryAdventures'':
** Cubi Clans are led by a Tri-winged Succubus or Incubus, who are as close to immortal as one can get with a an ungodly long lifespan and are so powerful very few dare to challenge them. The catch is they cannot have children of their own, and while it is possible to [[http://www.missmab.com/Comics/Vol_1222.php convert]] non-blood relatives to their clan there must be at least one fertile member of the clan alive who has had a child with the prospective member. The character Fa'lina shows how this can be bad, being a clan leader and being the last surviving member of said clan.
** In addition to Cubi, no new members of the Fae race may be born until living members willingly and deliberately die. They can have children with just about anything, but, [[http://www.missmab.com/Demo/HG06.php well...]] The problem is that the fae race has only so many souls to go around, and nothing can be done to increase that number. That's why a fae has to die before a new one can be born -- the dying fae's soul is reincarnated in the newborn fae.
** Destania's clan leader Cyra is in a similar boat as Fa'lina. Destania is her ''last'' surviving "child" and she can't even speak with her anymore since Destania has given up dreaming -- and Cyra mostly communicates in dreams. [[spoiler: So she's absolutely ''thrilled'' when she gets the chance to [[http://missmab.com/Comics/Vol_1002.php speak with her "grandson" Dan]]]].
** Most of the other LongLived races such as Demons don't seem to have this problem. Overpopulation isn't an issue since Furrae is dangerous enough that most people, Beings and Creatures alike, do not live to die of old age anyway. The Angels' birthrate has been waning in recent years for some reason, and they are very worried about becoming a DyingRace.
* The elves of ''WebComic/ErrantStory'' previously had an extremely low fertility rate, which is part of the reason why taking on [[InterspeciesRomance human]] [[MayflyDecemberRomance lovers]] was so popular among them; as Sarine put it, elves could "try for centuries to have an elven child with no success, or they could go fuck a human and have [[HalfHumanHybrid the next best thing]]." In the wake of the Errant Wars, the elven fertility rate seems to have dropped from "low" to "zero," as the last elven child born is now some 1,500 years old.\\
When [[http://www.errantstory.com/2010-07-12/4871 Meji finally starts 'talking' with Senilus]], one of the things she learns is that the something went wrong when the 'gods' made one of the races; the race would lose the ability to reproduce itself after 427 generations. Since the first two races the 'gods' made weren't ''able'' to reproduce, and the last race made by the gods is generally agreed to be the trolls, it is very strongly indicated that the race in question is the elves. ''But'' they are still fertile with humans, since errant Meji is only 17, and errants can be very long-lived. The elves originally took advantage of this to increase their population, until one powerful errant mage went mad for some reason and went on a rampage. The elves thought it was an inherent problem with errants and forbade future errant births.
* Parodied in ''WebComic/IrregularWebcomic'''s "Fantasy" storyline, where it's pointed out that Elven longevity also means that young Elves take ''centuries'' to grow past adolescence. As a result, the Elves invented prophylactics before they discovered how to use fire.
* The Bradicor of Ghanj-Rho in ''Webcomic/SchlockMercenary'' have, individually, [[TimeAbyss survived millions of years]] and watched the evolution of intelligent life forms, but are indifferent to the gradual extinction of their species. The heroes end up accidentally flattening their last female during first contact and dooming them to extinction. The Bradicor react more with annoyance than anything else seeing how they were already sterile.
* In ''Webcomic/{{Jack|DavidHopkins}}'' there are some people who have missed their chance to die for some reason, their biology is frozen at the point where they should have died and they can't reproduce as a result. [[http://www.pholph.com/strip.php?id=5&sid=3375 And it appears that sterile immortality was intentional.]]
* ''WebComic/{{Drowtales}}'' plays with this, in that drow are TheAgeless[[note]]Something WordOfGod has said is ''technically'' not true in that they have a finite lifespan of somewhere over 1000, but almost none of them survive long enough to reach this[[/note]] but some, including Ash'waren and Zala'ess, are known for their [[MassiveNumberedSiblings extremely large families]], but they tend to be the outliers on the far end of the scale. Meanwhile Diva'ratrika Val'Sharen is over a thousand and has only had five (surviving) daughters and one son, which the suggestion that politics has played a role in this. Meanwhile, during a 15 year timeskip, Mel'arnach has three children, which suggests fae are able to have multiple kids within a short amount of time with relatively little trouble, and drow in particular elevate motherhood to a sacred level, with one character's ''losing'' her ability to have more children playing a critical role in her motivations and actions. The CrapsackWorld nature of the environment means that despite people having lots of kids the population has stayed relatively stable due to the high chance of death.
* The Enchanters in ''Webcomic/AtArmsLength'' are fully capable of having children at any time, but social norms tend to prevent this. Also, the biological clock normally doesn’t start ticking until a few millennia, eliminating the desire to have children for quite a while. Enchanters who have children while they’re still relatively young, or have more then one, are typically frowned upon.
* In ''WebComic/ElGoonishShive'', Immortals are capable of having children, at least to some degree. Most do not seem to do so, though. "Half-Immortals" (called "elves" in the series jargon), the offspring of an Immortal and an ordinary human, are confirmed to be sterile. No word on what happens if two Immortals attempt procreation.

[[folder:Western Animation]]
* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'':
** Celestia and Luna seem to follow this trope. They have both lived at least a thousand years, possibly much longer, and their only onscreen relatives are a niece and a nephew (and presumably their offscreen relatives). The existence of Age spells only accessible to really powerful unicorns further complicates things, as their immortality may not even be natural. [[spoiler:Said niece and nephew aren't even blood relatives. As far as we know, the sisters have no other living relatives.]]
** However the real reason seems to be they just don't have a husband.
** ''Literature/TheJournalOfTheTwoSisters'' implies that natural alicorns, as opposed to ponies changed via magic, are apparently a very rare and LongLived pony race
** Dragons are capable of producing offspring, though the rate at which they do is not established and one can assume they follow the rule of longetivity as most dragons do.
* Fairies in ''WesternAnimation/TheFairlyOddparents'' are forbidden to have children, mostly because A) they're immortal and don't really need to, B) A newborn fairy's RealityWarper powers are dangerously unstable and C) the last one born was [[MikeNelsonDestroyerOfWorlds Cosmo]]. The only reason Poof exists is that [[LoopholeAbuse no one forbade their godchildren from wishing for them]].
** More accurately, Jorgen keeps forgetting to implement that rule, so it's possible that there may have been more Fairy babies brought into life (explaining Poof's peers in nursery school.) Poof seems to be a big case because of whom his parents and godbrother is.
* Crystal Gems in ''WesternAnimation/StevenUniverse'' [[TheAgeless don't age]], but Rose is the only one known to have had a child ([[HalfHumanHybrid Steven]]), which resulted in her child being born with her [[HeartDrive gem]]. WordOfGod states that Crystal Gems don't normally reproduce ''at all'', and whatever Rose did was extremely out of the ordinary. [[spoiler:Rose even stated in her {{Video Will|s}} that her and Steven can't exist at the same time, and she's ''becoming'' (half of) him as much as she's giving birth to him.]] Ultimately, it turns out gems (as individuals and [[ServantRace a species]]) are born artificially, using machines [[spoiler:that suck LifeEnergy out of planets. The Homeworld Gems using the Earth to create more Gems is actually what caused [[GreatOffscreenWar the Crystal Gems to side against them]].]]

[[folder:Real Life]]
* Averted with amoebae, and other single celled organisms that reproduce by binary fission. When you split in half (as opposed to budding off a daughter cell), you can consider both resulting amoebae to be an extension of the life of the parent. In short, every single amoeba on the planet is the very first amoeba. They're immortal and reproduce like crazy. Good thing they're fairly low on the food chain, so their hypothetical immortality isn't much of a problem.
* Throughout history people have attempted to discover the secret to eternal life and [[http://en.wikipedia.org/wiki/Aubrey_de_Grey Aubrey De Grey]] is probably the most famous example in modern science. He has come up with his own theories and has even gone so far as to speculate that, once technology can stop and reverse aging, people will have to file a form to have children and then wait for other people to die (through natural causes or requested suicide) to be given the go-ahead.
* Thought experiments on population growth rates suggest that extending lifespan needn't necessarily produce an ExplosiveBreeder, as it's really the age ''at first reproduction'' that determines how fast a population grows. Mathematically, having a breeding female live forever will do less to increase birth rates than having her produce a daughter (who'll breed early in turn) slightly sooner.
* This idea is truth in television in human communities insomuch as the childbirth rate of a country appears to be inversely related to its average lifespan. This is attributed to things like education, not seeing everyone around you die young (which tends to cause survivor lust), and good healthcare that improves lifespans and reduces infant mortality, meaning people don't need to have as many children to guarantee some survive. More developed countries also tend to have less of a primary-industry focus, meaning children are a net drain on assets rather than a source of income. State welfare and wealth in general also means parents aren't as reliant on children to support them in their old age.
* Because human oocytes (eggs) are produced by a woman's ovaries before she, herself, is born, an immortal woman's capacity for natural reproduction would inevitably expire when her supply runs out, even if she never goes through menopause (assuming the science at some point won't be able to reboot the ova production mechanism, of course). She could, however, give birth to a baby conceived ''in vitro'' from a donor egg.
** This has [[ScienceMarchesOn recently]] been {{Jossed}} by [[http://www.nature.com/news/egg-making-stem-cells-found-in-adult-ovaries-1.10121 the discovery of egg-producing stem cells]] (so-called [[https://en.wikipedia.org/wiki/Oogonium#Oogonial_stem_cells oogonial stem cells]]) in adult women's ovaries. Regardless of this, menopause obviously still renders women infertile.
** There are also services now that preserve a woman's egg in case she doesn't have a baby before menopause. This is the same as the process mentioned above with the only difference is that it's still her own baby.
* The [[http://www.cracked.com/article_18471_5-animals-that-are-terrifyingly-hard-to-kill_p2.html immortal jellyfish]] doesn't die; it turns back into a baby and starts over. A total aversion because it also reproduces quickly.[[note]]That tends to happen when you're the ocean's snack food.[[/note]]