Well, I've got a minority opinion of incest, judging by the posts here.
Inbreeding - e.g., incest - has long been used by animal breeders to breed in a particular trait, to reinforce that trait. After generations of inbreeding the strain, you've got smaller dogs, or differently-colored rabbits, or longer-haired cats, or larger cattle. Inbreeding has been done to a great degree with the mice that are used in all sorts of experiments.
Bottlenecks in populations have been shown to produce a higher level of deformities in the first few generations. But, given a lack of medical care, and that those without the bad gene dying before they can reproduce, after about 4 generations that particularly bad, recessive, and lethal gene is removed from the population's gene pool.
Lines of monarchs have been severely inbred for hundreds or thousands of years. The royal families of Europe and of North Africa have some hereditary conditions - such as hemophilia and color blindness. The pharaohs of Ancient Egypt were even more inbred over a dynasty, and they too had some genetic disorders that we can tell from looking at mummies and ascertain from reading histories. In Ancient Egypt, pharaohs married their sisters and produced the next Pharaoh - and his wife. They had a high coefficient of being inbred if the pharaoh had parents who were brother and sister who were descended from parents who were brother and sister who were descended from parents who were brother and sister... They still mostly live to adulthood with few problems. Until the last few generations of European monarchs, there was no access to medical care that could adequately address such problems.
Some of these foetuses with severe genetic birth defects are, indeed, miscarried. However, fewer miscarriages or spontaneous abortions happen when the parents are first cousins, with modern studies. That's believed to be because of the consanguinity making the body chemistry between mother and foetus more harmonious - her body is less likely to attack it as a foreign protein.
Rates for marrying a relative vary between nations and societies. Worldwide, approximately 20% of all marriages occur between first cousins. In the US, it's about 1:250 while in Japan it's about 1:4. It's perfectly legal in most countries, including all of Europe. It's illegal in 26 US States.
Even at that, the rate for birth defects - e.g., Down's Syndrome is much higher for a mother who is over 40 than the rate is even for a brother/sister pairing. If we're going to use the risk of birth defects as a reason to disallow a particular type of sexuality or even potentially procreative sexuality, it would be far better to allow cousin marriages (and children of marriages) than to allow women over 40 to marry, be sexually active, or have children. See http://www.slate.com/blogs/blogs/humanna...rhood.aspx
"Children of non-related couples have a 2-3% risk of birth defects, as opposed to first cousins having a 4-6% risk. Genetic counseling is available for those couples that may be at a special risk for birth defects (e.g. You have a defect that runs in your family) In plain terms first cousins have at a 94 percent + chance of having healthy children. Check the links section for more information on genetic counselors. The National Society of Genetic Counselors estimated the increased risk for first cousins is between 1.7 to 2.8 percent" http://www.cousincouples.com/?page=facts
Note too that no one alive is any more distant from anyone else alive than 27th cousin. Most of us are much closer than that - especially if we are of the same race, live in or come from the same country or region. And, genetic deformities occur with people who are not known to be related, or are known to be related only very distantly - e.g., 5th cousins or more.
The bottom line is that I don't see anything inherently wrong with incest, per se. I do see problems when it's confounded by someone being a prepubescent child, or some sort of relationship where the power balance was such that someone could not "say no". In those cases, it's nothing more or less than rape or child molestation. If both people are adults, it's fine.
In the animal breeding case, especially the inbreeding done to somehow improve a line of animals, or in the observed cases of genetic bottlenecks requiring inbreeding, the one thing that keeps it going, or allows it to in some way improve that bloodline is that those with the observed manifestation of the deformity absolutely must be culled. That is, that they are not allowed to reproduce - culled does NOT necessitate killing them! In the case of show-animal breeding, the culls are sold as "pet quality", and either don't reproduce or don't reproduce back with the show quality animals. In the case of humans, they could simply be sterilized. But, somehow that's "wrong" because we're human but it's not "wrong" to sterilize an animal with a defect.
I'll come back and answer the other questions about various sexual practices and "orientations".
Inbreeding - e.g., incest - has long been used by animal breeders to breed in a particular trait, to reinforce that trait. After generations of inbreeding the strain, you've got smaller dogs, or differently-colored rabbits, or longer-haired cats, or larger cattle. Inbreeding has been done to a great degree with the mice that are used in all sorts of experiments.
Bottlenecks in populations have been shown to produce a higher level of deformities in the first few generations. But, given a lack of medical care, and that those without the bad gene dying before they can reproduce, after about 4 generations that particularly bad, recessive, and lethal gene is removed from the population's gene pool.
Lines of monarchs have been severely inbred for hundreds or thousands of years. The royal families of Europe and of North Africa have some hereditary conditions - such as hemophilia and color blindness. The pharaohs of Ancient Egypt were even more inbred over a dynasty, and they too had some genetic disorders that we can tell from looking at mummies and ascertain from reading histories. In Ancient Egypt, pharaohs married their sisters and produced the next Pharaoh - and his wife. They had a high coefficient of being inbred if the pharaoh had parents who were brother and sister who were descended from parents who were brother and sister who were descended from parents who were brother and sister... They still mostly live to adulthood with few problems. Until the last few generations of European monarchs, there was no access to medical care that could adequately address such problems.
Some of these foetuses with severe genetic birth defects are, indeed, miscarried. However, fewer miscarriages or spontaneous abortions happen when the parents are first cousins, with modern studies. That's believed to be because of the consanguinity making the body chemistry between mother and foetus more harmonious - her body is less likely to attack it as a foreign protein.
Rates for marrying a relative vary between nations and societies. Worldwide, approximately 20% of all marriages occur between first cousins. In the US, it's about 1:250 while in Japan it's about 1:4. It's perfectly legal in most countries, including all of Europe. It's illegal in 26 US States.
Even at that, the rate for birth defects - e.g., Down's Syndrome is much higher for a mother who is over 40 than the rate is even for a brother/sister pairing. If we're going to use the risk of birth defects as a reason to disallow a particular type of sexuality or even potentially procreative sexuality, it would be far better to allow cousin marriages (and children of marriages) than to allow women over 40 to marry, be sexually active, or have children. See http://www.slate.com/blogs/blogs/humanna...rhood.aspx
"Children of non-related couples have a 2-3% risk of birth defects, as opposed to first cousins having a 4-6% risk. Genetic counseling is available for those couples that may be at a special risk for birth defects (e.g. You have a defect that runs in your family) In plain terms first cousins have at a 94 percent + chance of having healthy children. Check the links section for more information on genetic counselors. The National Society of Genetic Counselors estimated the increased risk for first cousins is between 1.7 to 2.8 percent" http://www.cousincouples.com/?page=facts
Note too that no one alive is any more distant from anyone else alive than 27th cousin. Most of us are much closer than that - especially if we are of the same race, live in or come from the same country or region. And, genetic deformities occur with people who are not known to be related, or are known to be related only very distantly - e.g., 5th cousins or more.
The bottom line is that I don't see anything inherently wrong with incest, per se. I do see problems when it's confounded by someone being a prepubescent child, or some sort of relationship where the power balance was such that someone could not "say no". In those cases, it's nothing more or less than rape or child molestation. If both people are adults, it's fine.
In the animal breeding case, especially the inbreeding done to somehow improve a line of animals, or in the observed cases of genetic bottlenecks requiring inbreeding, the one thing that keeps it going, or allows it to in some way improve that bloodline is that those with the observed manifestation of the deformity absolutely must be culled. That is, that they are not allowed to reproduce - culled does NOT necessitate killing them! In the case of show-animal breeding, the culls are sold as "pet quality", and either don't reproduce or don't reproduce back with the show quality animals. In the case of humans, they could simply be sterilized. But, somehow that's "wrong" because we're human but it's not "wrong" to sterilize an animal with a defect.
I'll come back and answer the other questions about various sexual practices and "orientations".
