Kanpeki na Imouto wa Tabun Hentai - Ch. 18

[MangaDex]

 

[smormu]

Did you know that hypothetically modern medical technology could allow two siblings to have children together with zero increased risk? Using preimplantation genetic testing you can test embryos to see what genetics they have. This can allow you to select an embryo which has a good amount of MHC variation, no genetic disorders and depending on how many good embryos you have you may even be able to then select for desirable traits like intelligence and height. Modern medicine can allow you to have perfect babies with your sister, just something to think about. It can be expensive though, it’s tens of thousands of dollars.

 

[Moshu_Reads]

Did you know that hypothetically modern medical technology could allow two siblings to have children together with zero increased risk? Using preimplantation genetic testing you can test embryos to see what genetics they have. This can allow you to select an embryo which has a good amount of MHC variation, no genetic disorders and depending on how many good embryos you have you may even be able to then select for desirable traits like intelligence and height. Modern medicine can allow you to have perfect babies with your sister, just something to think about. It can be expensive though, it’s tens of thousands of dollars.

just admit you like incest dude

 

[JamesMoriarty]

Did you know that hypothetically modern medical technology could allow two siblings to have children together with zero increased risk? Using preimplantation genetic testing you can test embryos to see what genetics they have. This can allow you to select an embryo which has a good amount of MHC variation, no genetic disorders and depending on how many good embryos you have you may even be able to then select for desirable traits like intelligence and height. Modern medicine can allow you to have perfect babies with your sister, just something to think about. It can be expensive though, it’s tens of thousands of dollars.

Even ignoring all of modern technology, an offspring produced by siblings doesn't really have THAT much more risk than the average population. The problem comes when incest continues to be practiced over several generations. The second problem is that, IRL, the ones more likely to commit incest are the ones messed up enough to keep doing it through generations... in a short period of time...

 

[smormu]

Even ignoring all of modern technology, an offspring produced by siblings doesn't really have THAT much more risk than the average population. The problem comes when incest continues to be practiced over several generations. The second problem is that, IRL, the ones more likely to commit incest are the ones messed up enough to keep doing it through generations... in a short period of time...

The exact rate of complications in children born to parents who are brother and sister is pretty hard to pin down. For cousins it is easy because cousin marriage is significantly more common, the rate of birth defects goes from 2-3% to 4-6%. For siblings it’s significantly harder to get an exact number because sibling incest isn’t nearly as common and when it is practiced it’s usually in secret. Doing case studies is unreliable since healthy inbred children are less likely to come to the attention of medical personnel.

This math may be BS, but here I go again

1st cousins share 12.5% of their DNA and they have a kinship coefficient of 6.25%, meaning that at any given locus there is a one sixteenth chance that the genes are identical by descent between the first cousins. In their children there is a one in four chance that they inherit the shared gene from both parents. Because there are two possible homozygous genotypes and only one of them is harmful the kinship coefficient is divided by 2. Half of 6.25% is 3.12% and when you add the 2.5% base risk of complications on top of that you get 5.62%

If my sophisticated and supremely advanced formula of K/2+2.5 is accurate then siblings should have a rate of birth defects of 15% and Half siblings would have a rate of complications of 8.75%. K is kinship coefficient.

EDIT: After consulting ChatGPT I have seen that I have made a mathematical error and I do not believe that this is accurate
EDIT 2: I have adjusted my math to account for the fact that siblings share two parents and first cousins share two grandparents
EDIT 3: The second model ran into the problem of half siblings have the exact same rate of complications as first cousins, I’ve simplified the model to fix this.
————————————————————————————————————

As for your point about people coming from families which already practiced inbreeding being more likely to inbreed, I have a theory that relates to this.

There is a phenomenon called genetic sexual attraction wherein close relatives who are raised apart and later reunited as adults feel intense sexual attraction to each other. The main theory behind this is that humans naturally seek mates who are genetically similar to them, this is called assortative mating and is generally considered to be true. The westermark effect, which is the main incest aversion strategy humans use, works by people negatively sexually imprinting on people we lived with in early childhood, because they are likely our siblings. This way we can have assortative mating without automatically inbreeding with our siblings, but if you aren’t raised with your siblings the westermark effect cannot work and the strong genetic similarity you have with your siblings is extremely attractive. This is the main idea behind GSA.

I have a theory that in some people their instinct for assortative mating is strong enough that it overpowers the westermark effect and causes attraction in siblings even if they grew up together. Why would we have incest taboos if all people naturally avoided it on their own without being forced to? Perhaps there are some people who by nature would practice incest and need taboo and law to keep them from doing this. I also think that weaker westermark aversion could be a factor.

Under this theory people who inbreed have naturally stronger instincts for assortative mating. Their children would be more genetically similar to one another than usual due to inbreeding and would thus have increased attraction. Of course attraction could decrease as a result of them having reduced fitness due to inbreeding, but I think this theory is neat.

 

[darekpawlo]

The exact rate of complications in children born to parents who are brother and sister is pretty hard to pin down. For cousins it is easy because cousin marriage is significantly more common, the rate of birth defects goes from 2% to 4%. For siblings it’s significantly harder to get an exact number because sibling incest isn’t nearly as common and when it is practiced it’s usually in secret. Doing case studies is unreliable since healthy inbred children are less likely to come to the attention of medical personnel.

This math may be BS, but here I go again

1st cousins share 12.5% of their DNA and they have a relationship coefficient of 6.25%, meaning that at any given locus there is a one sixteenth chance that the genes are identical by descent between the first cousins. In their children there is a one in four chance that they inherit the shared gene from both parents. One fourth of 6.25% is 1.5625% which when added to the 2% baseline risk of the general population comes out to roughly 3.56%, which is close to the 4% rate of birth defects found in first cousin marriages. Of course this assumes that there is only one genetic disorder in the family to worry about, if there are multiple then the math gets a lot more complicated.

If my sophisticated and supremely advanced formula of r/4+2 is accurate then siblings should have a rate of birth defects of 8.25%, but I consider this to be a lowball estimate of the rate of complications.

————————————————————————————————————

As for your point about people coming from families which already practiced inbreeding being more likely to inbreed, I have a theory that relates to this.

There is a phenomenon called genetic sexual attraction wherein close relatives who are raised apart and later reunited as adults feel intense sexual attraction to each other. The main theory behind this is that humans naturally seek mates who are genetically similar to them, this is called assortative mating and is generally considered to be true. The westermark effect, which is the main incest aversion strategy humans use, works by people negatively sexually imprinting on people we lived with in early childhood, because they are likely our siblings. This way we can have assortative mating without automatically inbreeding with our siblings, but if you aren’t raised with your siblings the westermark effect cannot work and the strong genetic similarity you have with your siblings is extremely attractive. This is the main idea behind GSA.

I have a theory that in some people their instinct for assortative mating is strong enough that it overpowers the westermark effect and causes attraction in siblings even if they grew up together. Why would we have incest taboos if all people naturally avoided it on their own without being forced to? Perhaps there are some people who by nature would practice incest and need taboo and law to keep them from doing this. I also think that weaker westermark aversion could be a factor.

Under this theory people who inbreed have naturally stronger instincts for assortative mating. Their children would be more genetically similar to one another than usual due to inbreeding and would thus have increased attraction. Of course attraction could decrease as a result of them having reduced fitness due to inbreeding, but I think this theory is neat.

Do you, by any chance have sibling that is opposite sex of you?

 

[smormu]

Do you, by any chance have sibling that is opposite sex of you?

I have an older sister (6 years older) who is a short fat crazy hoe, totally not my type. I highly suspect that if I had a sister who was closer to me in age and was more my type that I would be an enormous siscon.

I find the topic of incest and inbreeding to be fascinating because it’s a surprisingly deep topic. It touches on genetics, evolution, taboo, psychology, sexuality, anthropology, there’s a lot to it. It’s also fucking hot

 

[darekpawlo]

I have an older sister who is a short fat crazy hoe, totally not my type. I highly suspect that if I had a sister who was closer to me in age and was more my type that I would be an enormous siscon.

I find the topic of incest and inbreeding to be fascinating because it’s a surprisingly deep topic. It touches on genetics, evolution, taboo, psychology, sexuality, anthropology, there’s a lot to it. It’s also fucking hot

Sorry to hear that you lost sister lottery

 

[BlackElite]

Did you know that hypothetically modern medical technology could allow two siblings to have children together with zero increased risk? Using preimplantation genetic testing you can test embryos to see what genetics they have. This can allow you to select an embryo which has a good amount of MHC variation, no genetic disorders and depending on how many good embryos you have you may even be able to then select for desirable traits like intelligence and height. Modern medicine can allow you to have perfect babies with your sister, just something to think about. It can be expensive though, it’s tens of thousands of dollars.

Cutting and reassembling DNA sequences? Picking the best and throwing the bad? If yes then what you're speaking of is currently banned. Usage of tools like CRISPR to modify genetics on human except for life-saving medical operation is unethical and frowned upon.

 

[smormu]

Cutting and reassembling DNA sequences? Picking the best and throwing the bad? If yes then what you're speaking of is currently banned. Usage of tools like CRISPR to modify genetics on human except for life-saving medical operation is unethical and frowned upon.

PGT is not modification and has been used for decades. It’s done during in vitro fertilization, basically they take a fertilized egg cell from a blastocyst, DNA test it and then you can make a judgement on whether or not to implant it. It’s primarily used for couples who both carry a genetic disorder and want to eliminate the risk of having their children suffer from it, but you can also use it to cherry pick the best embryo.

 

[subliminal]

The exact rate of complications in children born to parents who are brother and sister is pretty hard to pin down. For cousins it is easy because cousin marriage is significantly more common, the rate of birth defects goes from 2-3% to 4-6%. For siblings it’s significantly harder to get an exact number because sibling incest isn’t nearly as common and when it is practiced it’s usually in secret. Doing case studies is unreliable since healthy inbred children are less likely to come to the attention of medical personnel.

This math may be BS, but here I go again

1st cousins share 12.5% of their DNA and they have a kinship coefficient of 6.25%, meaning that at any given locus there is a one sixteenth chance that the genes are identical by descent between the first cousins. In their children there is a one in four chance that they inherit the shared gene from both parents. One fourth of 6.25% is 1.5625% which when added to the 2-3% (let’s just say 2.5) baseline risk of the general population comes out to 4.06%, which is within the 4-6% rate of birth defects found in first cousin marriages. Cousins share two grandparents of course and if one of them carries a recessive disorder then why can’t the other? That would double that 1.56 figure to 3.25 which when added to 2.5% becomes 5.75%.

If my sophisticated and supremely advanced formula of K/4*2+2.5 is accurate then siblings should have a rate of birth defects of 15%. K is kinship coefficient.

EDIT: After consulting ChatGPT I have seen that I have made a mathematical error and I do not believe that this is accurate
EDIT 2: I have adjusted my math to account for the fact that siblings share two parents and first cousins share two grandparents
————————————————————————————————————

As for your point about people coming from families which already practiced inbreeding being more likely to inbreed, I have a theory that relates to this.

There is a phenomenon called genetic sexual attraction wherein close relatives who are raised apart and later reunited as adults feel intense sexual attraction to each other. The main theory behind this is that humans naturally seek mates who are genetically similar to them, this is called assortative mating and is generally considered to be true. The westermark effect, which is the main incest aversion strategy humans use, works by people negatively sexually imprinting on people we lived with in early childhood, because they are likely our siblings. This way we can have assortative mating without automatically inbreeding with our siblings, but if you aren’t raised with your siblings the westermark effect cannot work and the strong genetic similarity you have with your siblings is extremely attractive. This is the main idea behind GSA.

I have a theory that in some people their instinct for assortative mating is strong enough that it overpowers the westermark effect and causes attraction in siblings even if they grew up together. Why would we have incest taboos if all people naturally avoided it on their own without being forced to? Perhaps there are some people who by nature would practice incest and need taboo and law to keep them from doing this. I also think that weaker westermark aversion could be a factor.

Under this theory people who inbreed have naturally stronger instincts for assortative mating. Their children would be more genetically similar to one another than usual due to inbreeding and would thus have increased attraction. Of course attraction could decrease as a result of them having reduced fitness due to inbreeding, but I think this theory is neat.

There's actually a study that looked at medical records of native brits using biobank data to pick out individuals with genetic patterns of close inbreeding parent-child/sibling. I've not read it in a while I think there were rates of one in a couple of thousand people being inbred so it is much more common than one might think.
Extreme inbreeding in a European ancestry sample from the contemporary UK population
https://www.nature.com/articles/s41467-019-11724-6.pdf

And I could direct you to consider the wealth of genetic studies built up on both livestock and laboratory animals. There are stats on the rates and effects of inbreeding depression.
Reading old records of livestock breeding you find the practice of linebreeding where say a farmer wanted to magnify the genes of a superior bull by breeding it to its daughters or sisters to get calves that were 75% similar to it, it seems to have been more common as a way to multiply up elite genetics prior to the introduction of ai since people wanted bulls with as much common genes as possible of this elite bull.
I've recently been reading a fascinating old book from the 50s that described a friesian caw "Manningford Faith Jan Graceful" who held the world record for highest lifetime milkyield back in the 50s with 145 tons of milk across 17.5 years, when she died she apparently had an obituary in the national newspapers. Both her sire and dam shared the same sire. I couldn't find any records of their respective dams or their relatedness that way. in another chapter they describe a farmer who had analysed various pedigree records to try and pick out a bull that magnified the relatedness of his herd to a legendary elite bull called Cirres, he ended up buying a bull that even further magnified the relation of his cows to that original bull and surprisingly the calves from this grew up to be winners too.

So I guess in conclusion Inbreeding works when it works and it doesn't when it doesn't since it only magnifies what's there.

 

[smormu]

There's actually a study that looked at medical records of native brits using biobank data to pick out individuals with genetic patterns of close inbreeding parent-child/sibling. I've not read it in a while I think there were rates of one in a couple of thousand people being inbred so it is much more common than one might think.
Extreme inbreeding in a European ancestry sample from the contemporary UK population
https://www.nature.com/articles/s41467-019-11724-6.pdf

And I could direct you to consider the wealth of genetic studies built up on both livestock and laboratory animals. There are stats on the rates and effects of inbreeding depression.
Reading old records of livestock breeding you find the practice of linebreeding where say a farmer wanted to magnify the genes of a superior bull by breeding it to its daughters or sisters to get calves that were 75% similar to it, it seems to have been more common as a way to multiply up elite genetics prior to the introduction of ai since people wanted bulls with as much common genes as possible of this elite bull.
I've recently been reading a fascinating old book from the 50s that described a friesian caw "Manningford Faith Jan Graceful" who held the world record for highest lifetime milkyield back in the 50s with 145 tons of milk across 17.5 years, when she died she apparently had an obituary in the national newspapers. Both her sire and dam shared the same sire. I couldn't find any records of their respective dams or their relatedness that way. in another chapter they describe a farmer who had analysed various pedigree records to try and pick out a bull that magnified the relatedness of his herd to a legendary elite bull called Cirres, he ended up buying a bull that even further magnified the relation of his cows to that original bull and surprisingly the calves from this grew up to be winners too.

So I guess in conclusion Inbreeding works when it works and it doesn't when it doesn't since it only magnifies what's there.

Different animals have different levels of genetic load and different tolerance for inbreeding, what’s applicable to cows is not necessarily applicable to humans. I have heard about the UK bio bank study, it’s pretty interesting, but it’s not necessarily the most accurate way to find out the rate of complications. Ideally we would just get 50 pairs of brothers and sisters and tell them to make babies so we can collect data, but the ethics committee nerds wouldn’t allow it.

A very interesting case of inbreeding in humans you should look into is the Ptolemaic dynasty. They practiced sibling inbreeding for almost three hundred years and at the end of their dynasty they were still producing competent people. Cleopatra was a veritable genius and she was far more inbred than Charles the second was. Why were the Ptolemies able to inbreed between siblings for 300 years and produce one of the greatest geniuses of the ancient world, but the Habsburgs inbreeding between cousins and uncles and nieces for a little over a century produced Charles the second who was such a dysgenic creature.

 

[subliminal]

Different animals have different levels of genetic load and different tolerance for inbreeding, what’s applicable to cows is not necessarily applicable to humans. I have heard about the UK bio bank study, it’s pretty interesting, but it’s not necessarily the most accurate way to find out the rate of complications. Ideally we would just get 50 pairs of brothers and sisters and tell them to make babies so we can collect data, but the ethics committee nerds wouldn’t allow it.

A very interesting case of inbreeding in humans you should look into is the Ptolemaic dynasty. They practiced sibling inbreeding for almost three hundred years and at the end of their dynasty they were still producing competent people. Cleopatra was a veritable genius and she was far more inbred than Charles the second was. Why were the Ptolemies able to inbreed between siblings for 300 years and produce one of the greatest geniuses of the ancient world, but the Habsburgs inbreeding between cousins and uncles and nieces for a little over a century produced Charles the second who was such a dysgenic creature.

Ptolemaic dynasty

Been there read that, you're actually grossly under painting it. Everyone in egypt was marrying their sibling, accoding to roman era census records 40% of egyptian men with a sister married her. They'd probably been doing this for hundreds of years before.

You've also fallen for the charles the second propaganda, there's a report that analysed the hapsburg birth records and found the lineage got healthier on average with every generation with gradually falling rates of child mortality. The fixation is always put upon charles but he wasn't typical.
also if you've not come across it yet, I recommend the 2008 paper about icelandic birth and marriage records that found peak fertility correlated with 3rd cousins while there was a decline in fertility with furthur distances
https://www.researchgate.net/public...en_the_Kinship_and_Fertility_of_Human_Couples

Try reading some of anthropologist Robin Fox's work if you can find it..

 

[Yuuki_Kataishi]

The exact rate of complications in children born to parents who are brother and sister is pretty hard to pin down. For cousins it is easy because cousin marriage is significantly more common, the rate of birth defects goes from 2-3% to 4-6%. For siblings it’s significantly harder to get an exact number because sibling incest isn’t nearly as common and when it is practiced it’s usually in secret. Doing case studies is unreliable since healthy inbred children are less likely to come to the attention of medical personnel.

This math may be BS, but here I go again

1st cousins share 12.5% of their DNA and they have a kinship coefficient of 6.25%, meaning that at any given locus there is a one sixteenth chance that the genes are identical by descent between the first cousins. In their children there is a one in four chance that they inherit the shared gene from both parents. Because there are two possible homozygous genotypes and only one of them is harmful the kinship coefficient is divided by 2. Half of 6.25% is 3.12% and when you add the 2.5% base risk of complications on top of that you get 5.62%

If my sophisticated and supremely advanced formula of K/2+2.5 is accurate then siblings should have a rate of birth defects of 15% and Half siblings would have a rate of complications of 8.75%. K is kinship coefficient.

EDIT: After consulting ChatGPT I have seen that I have made a mathematical error and I do not believe that this is accurate
EDIT 2: I have adjusted my math to account for the fact that siblings share two parents and first cousins share two grandparents
EDIT 3: The second model ran into the problem of half siblings have the exact same rate of complications as first cousins, I’ve simplified the model to fix this.
————————————————————————————————————

As for your point about people coming from families which already practiced inbreeding being more likely to inbreed, I have a theory that relates to this.

There is a phenomenon called genetic sexual attraction wherein close relatives who are raised apart and later reunited as adults feel intense sexual attraction to each other. The main theory behind this is that humans naturally seek mates who are genetically similar to them, this is called assortative mating and is generally considered to be true. The westermark effect, which is the main incest aversion strategy humans use, works by people negatively sexually imprinting on people we lived with in early childhood, because they are likely our siblings. This way we can have assortative mating without automatically inbreeding with our siblings, but if you aren’t raised with your siblings the westermark effect cannot work and the strong genetic similarity you have with your siblings is extremely attractive. This is the main idea behind GSA.

I have a theory that in some people their instinct for assortative mating is strong enough that it overpowers the westermark effect and causes attraction in siblings even if they grew up together. Why would we have incest taboos if all people naturally avoided it on their own without being forced to? Perhaps there are some people who by nature would practice incest and need taboo and law to keep them from doing this. I also think that weaker westermark aversion could be a factor.

Under this theory people who inbreed have naturally stronger instincts for assortative mating. Their children would be more genetically similar to one another than usual due to inbreeding and would thus have increased attraction. Of course attraction could decrease as a result of them having reduced fitness due to inbreeding, but I think this theory is neat.

.... Yeah I'm not gonna read this late at night. I'll read it tomorrow after school xd