Fantasy Genetics

[Steve]

A while back, I posted some topics regarding a campaign idea I was working on involving an invasion from Faerie into Earth.

 

The basic idea was that humanoids and others from Faerie fled to Earth to escape a powerful Dark Lord. They settled among humans for a while during the early Dark Ages, the gates to Faerie remaining open enough to allow most of their magic to function, but at its most powerful near the gates. Then the big war against the Dark Lord happens, the end of which requires all the gates to be sealed. Magic fades to a bare trickle.

 

As a result, Faerie humanoids become more mortal, but not quite fully mortal. They are able to interbreed with humans. Their lifespans shrink to a maximum of 300-400 years from their former immortality. Some retain the ability to use magic, maybe a maximum of 30 Active Points.

 

My question in this post has to do with the genetics side of things. I am thinking the elf-like beings known as the Sidhe (the most common of the Fae imports) carry dominant genes. However, the ability to wield what little Fae magic remains in the world is a recessive gene among the Sidhe and their descendants.

 

What results could you see happening after a few centuries pass?

 

Another idea I was considering was that due to some quirk of genetics, pureblood Sidhe can breed with each other, but at a much lower rate of reproduction success than a Sidhe/Human pairing. Could a caste system develop in such a situation?

[Old Man]

Caste systems arise IRL just fine without any fantasy genetics, so I think you're good there.

 

The Sidhe genetics ramifications are pretty interesting. Depending on whether genealogy can be easily traced, you either get something like the Numenorian bloodlines from Middle-Earth, or you get magic-talented people popping up at random depending on whether they are born with the appropriate genes or not. Or even both. It could get even more interesting if the magic genes are not related to physical appearance at all, or if they come with a steep penalty like a susceptibility to iron.

[BhelliomRahl]

If there is no breeding control then the number of people with magic will decrease however the possibilty of a person spontanously developing magic is possible.

As the Genetic Trait for Magic is on a Recessive Chromosome it will need to be inherited from both parents. Meaning Half-Bloods will have no magic but will be carriers.

Without an understanding of Magic this intial realisation that their Half-Blood Children could lead to interesting directions in the development of Sidhe society if magic is to be maintained.

 

Quick Reference to Breeding Chance of Offspring having Magic or be a carrier Carrier: (For this chart Magic Users are classed as Sidhe)

Sidhe x Sidhe = Magic

Sidhe x Human = No Magic but Carrier

Carrier x Sidhe = 1 in 2 will have Magic. 1 in 2 will be Carriers

Carrier x Carrier = 1 in 4 have Magic. 1 in 2 will be Carriers

Carrier x Human = No Magic. 1 in 2 will be Carriers

---

 

If Sidhe wish to maintain magic in there culture this may lead to inbreeding to maintain the magic but this could lead to other genetic problems. So you could end up with a Caste of Pure Blooded Sidhe which have magic but are physically frail. This would depend on initial numbers of Sidhe on Earth.

 

This Pure-Blood Caste, possibly a ruling group, similair to Royalty could create Breeding Houses. Carriers or Halfbloods are collected and kept together in a houses. The people of these Houses have the simple task of Breeding. The Sidhe might even develop a Magic (Detect) to determine if a person is a carrier or Half-Blood if their is no physical signs. Those who are neither are asked to leave the house. Revenue could be gained by the previous mentioned Pure-Blood Caste (Mainly Males) coming to the House and paying for the privilege of mating with Courtesans (Prostitutes). Courtesans who have previously given birth to Magic-Users will become more sort after creating a structure to the House.

 

It would be very interesting.

 

The Book God Save the Queen (The Immortal Empire) by Kate Locke looks at a world in which a mutation of the Plague created Vampires, Werewolves and Goblins (Mix of Both) Mainly in the Aristocracy. Also Half-Bloods. The book goes into detail on the Genetics of breeding and how these groups effected the development of the world. Its a good read too.

[Steve]

The idea of magic use being tied to a vulnerability to traditional Fae weaknesses like cold iron is interesting, and I could see this version of Earth diverging into something a bit like Middle Earth with the people of Numenor.

[Clonus]

I have a fairy setting which has purebloods (fair folk who retain all of their fay qualities including extremely long life expectancies unless they succumb to "world weariness" or violence), changelings (fair folk who have been tainted by having being transformed into human or beast forms for extended periods of time), halflings (the result of intercourse between mundane life forms and the fay, which includes any "human" who can cast magic, as well near-humans who have some other kind of superhuman power), and humans (who can only cast magic if they acquire a fay familiar).

 

But I digress. Except that I kind of like the idea that the reason why the sidhe of your setting now only have moderately extended lifespans is because their "purebloods" all left or died due to lack of magic.

[Steve]

Purebloods would still exist, but only those who are descended of only Sidhe ancestors would be able to make that claim. I am playing with the idea of hybrid vigor to say that Human/Sidhe mixes are more prolific in their reproductive abilities. This would leave a gradually dwindling population of pureblooded Sidhe.

 

The rough timeline I am playing with is that the Sidhe fled to Earth in vast numbers prior to 1000 AD. The big battle against the Dark Lord took place at around 1000 AD. It is now several centuries past that in the world I am working with, maybe Pre-Renaissance times or just at the beginnings of the Renaissance.

 

The Sidhe and their descendants have multiplied over the centuries, integrating themselves into the cultures of Europe (maybe Asia and the Middle East too). I'm not sure how large to make their numbers though. Maybe some countries are more accepting than others of the Sidhe in their midst, since Sidhe sorcery would be valuable to a country's arsenal.

[NuSoardGraphite]

They should be all over asia and the middle east too. In the middle east you might have descendants of the ifreet or the djinn. In asia you may have descendants od the hsien (immortals) or descendants of various kami in Japan.

[Steve]

I was already thinking that different regions could have their own tribes of Fae arriving. So Europe gets the Sidhe, the Middle East get tribes of Djinn and Ifreet and Asia gets the Hsien. Smaller groups like Japan's Kami could come through as well.

 

If I start the initial population large, like 1-5% of humanity, that gives them instant significance. Over time, their numbers could grow, but I'm not sure how large to make the populations after five centuries of growth.

 

With their magic, even as muted as it is, normal humans could get crowded out of some places or the Fae could become the new nobility in regions.

[The Weapon]

EDIT: I realised that I assumed that the Sidhe don't continue to take human mates after the initial rush of hybrids. Sorry about that.

 

BhelliiomRahl describes the results of a single gene inheritance well, although I should add that any "human" who can caste magic is effectively Sidhe for this analysis. So a mage/mage mating will always produce a mage. However you don't need to limit yourself to a single gene. There could be multiple genes, perhaps coding for different types of magic, perhaps just adding different amounts of power. Needing 2 copies of 2 or more genes to have magic drastically reduces the probability of becoming a magic user. Needing at least 2 copies of magic genes, but not necessarily of the same one means mages can have non-mage babies. The math gets more complicated though so I'll deal with just the one gene.

 

Sidhe from different bloodlines could have different abilities. This may be because they have different alleles, or different genes in entirely different areas. An allele of a gene is a gene that can replace that gene, so I have a gene and you have either the same gene or an allele of it. So suppose three alleles h (regular human), w (recessive, grants water magic) and f (recessive, grants fire magic) the possible combinations are hh, hw, hf, ww, wf, ff. Now ww and ff clearly grant water and fire respectively, but what about hw? Does that make them a water user, a fire user or a steam user? Or can they use fire and water, possibly at lower power than "pure" users?

 

With regards to the population of humans with Sidhe genetics, the average number of Sidhe genes per 1,000 people in the population would remain stable unless they granted an advantage in survival or reproduction. Now magic is an advantage, but since it only grants that advantage if one carrier breeds with another, that means it depends on a) the percentage of the population with the genes and whether inbreeding is popular. Considering that Dark Ages peasants bred with people from the same village almost exclusively and that they therefore shared genes from previous generations, this might mean that carrier/carrier matings are far more common that simple random selection would indicate. Some communities would be relatively rich in magicians if particular family lines with the genes bred prodigously. Others would have the genes completely disappear. This is because genes in a stable population each person has an average of 2 offspring that get to breed and each offspring has a 50% chance of having the gene. So there is a 1/4 chance none of their children will have it. In a community with 3 carriers that means a 1/64 chance it will die out next generation and a 3/32 chance only one carrier remains*. This is reasonable with a gene rate of say 1% and 300 villagers. So if villages keep to themselves some will have to have no carriers at all.

 

The following is a formula for the probability of a carrier/carrier mating (assuming one recessive gene)

 

P(c+c) = P© *Max(P©, r)

Where P© is the probability that someone in the population is a carrier, Max(a, means the higher number out of a and b, and r is the degree of relatedness of the couple, the average probability that they will share a gene that isn't universal throughout the species.

Just remember to halve the relatedness going up a generation then add the relatedness of mother and father together for full siblings. Relatedness is 1/2 to parents, 1/2 to full siblings (1/2 relatedness to mother + 1/2 relatedness to father all divided by 2 on the way down again), 1/4 to half-sibliings, 1/4 to grandparents, 1/4 to uncles or aunts and 1/8 to first cousins. Historically first cousin weddings were common (and still are in many parts of the world) so the average relatedness of couples could easily be about 0.1. Someone who understood inheritance of magic could arrange sibling or parent/child matings to push up the odds of mage by up to fivefold. However this massively increases the chance of insanity, congenital defects, miscarriage or stillbirth.

 

 

If the Sidhe were 1% of the human population, 10% of them mated with humans giving an initial 0.1% Carrier/Half-breed rate then the probability of carrier/carrier matings (given relatedness average 0.1) would be 1/10,000 and rate of magic user births would be 1/40,000 babies whose parents aren't mages. If mages also held to the 0.1 relatedness to their mate pattern then 1% of their matings would be to other mages and would result in a mage. 18%** of their matings would be with a carrier and would result in a mage half the time (total 9%) for a total 10% chance a mage's baby is a mage. Assuming a stable population the average person born has 2 babies, so they have 0.2 mage babies on average. Take the formula for geometric increase and you get 25% as many mages born from mages as born from non-mages. This brings the total mages up to 1/32,000. England's population was between 1.2 and 2.6 million so there would be betweenn 37 and 82 mages born in each generation. Multiply this by how much longer they live than normal humans for the number of mages alive at any one time. Even assuming that they lived 5 times as long it's only about 400 max, so they concievably all be listed in one book, gather in one hall etc.

 

This assumes that neither being a carrier nor being a mage is an evoluntionary advantage (it may not be, sure mages are powerful, but are they targetted/exiled from society etc.?). Even if mages themselves don't breed helping out their relatives could spread the gene.

 

* This assumes everyone has 2 breeding kids, nobody has 4 while someone else has none and that being a carrier isn't an advantage.

** There is a 90% chance that won't they will share the first copy of the gene and a 90% chance they'll share the second copy for an 81% chance of no Sidhe gene. Since there's a 1% chance of a magic that leaves an 18% chance of a carrier.

[Steve]

EDIT: I realised that I assumed that the Sidhe don't continue to take human mates after the initial rush of hybrids. Sorry about that.

 

BhelliiomRahl describes the results of a single gene inheritance well, although I should add that any "human" who can caste magic is effectively Sidhe for this analysis. So a mage/mage mating will always produce a mage. However you don't need to limit yourself to a single gene. There could be multiple genes, perhaps coding for different types of magic, perhaps just adding different amounts of power. Needing 2 copies of 2 or more genes to have magic drastically reduces the probability of becoming a magic user. Needing at least 2 copies of magic genes, but not necessarily of the same one means mages can have non-mage babies. The math gets more complicated though so I'll deal with just the one gene.

 

Sidhe from different bloodlines could have different abilities. This may be because they have different alleles, or different genes in entirely different areas. An allele of a gene is a gene that can replace that gene, so I have a gene and you have either the same gene or an allele of it. So suppose three alleles h (regular human), w (recessive, grants water magic) and f (recessive, grants fire magic) the possible combinations are hh, hw, hf, ww, wf, ff. Now ww and ff clearly grant water and fire respectively, but what about hw? Does that make them a water user, a fire user or a steam user? Or can they use fire and water, possibly at lower power than "pure" users?

 

With regards to the population of humans with Sidhe genetics, the average number of Sidhe genes per 1,000 people in the population would remain stable unless they granted an advantage in survival or reproduction. Now magic is an advantage, but since it only grants that advantage if one carrier breeds with another, that means it depends on a) the percentage of the population with the genes and whether inbreeding is popular. Considering that Dark Ages peasants bred with people from the same village almost exclusively and that they therefore shared genes from previous generations, this might mean that carrier/carrier matings are far more common that simple random selection would indicate. Some communities would be relatively rich in magicians if particular family lines with the genes bred prodigously. Others would have the genes completely disappear. This is because genes in a stable population each person has an average of 2 offspring that get to breed and each offspring has a 50% chance of having the gene. So there is a 1/4 chance none of their children will have it. In a community with 3 carriers that means a 1/64 chance it will die out next generation and a 3/32 chance only one carrier remains*. This is reasonable with a gene rate of say 1% and 300 villagers. So if villages keep to themselves some will have to have no carriers at all.

 

The following is a formula for the probability of a carrier/carrier mating (assuming one recessive gene)

 

P(c+c) = P© *Max(P©, r)

Where P© is the probability that someone in the population is a carrier, Max(a, means the higher number out of a and b, and r is the degree of relatedness of the couple, the average probability that they will share a gene that isn't universal throughout the species.

Just remember to halve the relatedness going up a generation then add the relatedness of mother and father together for full siblings. Relatedness is 1/2 to parents, 1/2 to full siblings (1/2 relatedness to mother + 1/2 relatedness to father all divided by 2 on the way down again), 1/4 to half-sibliings, 1/4 to grandparents, 1/4 to uncles or aunts and 1/8 to first cousins. Historically first cousin weddings were common (and still are in many parts of the world) so the average relatedness of couples could easily be about 0.1. Someone who understood inheritance of magic could arrange sibling or parent/child matings to push up the odds of mage by up to fivefold. However this massively increases the chance of insanity, congenital defects, miscarriage or stillbirth.

 

 

If the Sidhe were 1% of the human population, 10% of them mated with humans giving an initial 0.1% Carrier/Half-breed rate then the probability of carrier/carrier matings (given relatedness average 0.1) would be 1/10,000 and rate of magic user births would be 1/40,000 babies whose parents aren't mages. If mages also held to the 0.1 relatedness to their mate pattern then 1% of their matings would be to other mages and would result in a mage. 18%** of their matings would be with a carrier and would result in a mage half the time (total 9%) for a total 10% chance a mage's baby is a mage. Assuming a stable population the average person born has 2 babies, so they have 0.2 mage babies on average. Take the formula for geometric increase and you get 25% as many mages born from mages as born from non-mages. This brings the total mages up to 1/32,000. England's population was between 1.2 and 2.6 million so there would be betweenn 37 and 82 mages born in each generation. Multiply this by how much longer they live than normal humans for the number of mages alive at any one time. Even assuming that they lived 5 times as long it's only about 400 max, so they concievably all be listed in one book, gather in one hall etc.

 

This assumes that neither being a carrier nor being a mage is an evoluntionary advantage (it may not be, sure mages are powerful, but are they targetted/exiled from society etc.?). Even if mages themselves don't breed helping out their relatives could spread the gene.

 

* This assumes everyone has 2 breeding kids, nobody has 4 while someone else has none and that being a carrier isn't an advantage.

** There is a 90% chance that won't they will share the first copy of the gene and a 90% chance they'll share the second copy for an 81% chance of no Sidhe gene. Since there's a 1% chance of a magic that leaves an 18% chance of a carrier.

This is good stuff.

 

The idea of multiple genes involved in magic ability is interesting, since I could see different versions of magical gifts passed down.

 

One gift I might make common to all Sidhe is the illusion magic of glamour, a tradition Fae ability. Past that, I could see a number of different gifts that could be gene-linked.

 

Perhaps the djinn and effreet tribes that migrated from the other world into Earth's Middle East have elemental magic genes that focus on air magic and fire magic respectively. The Dragonblooded from Exalted might be good sources there for inspiration