[Mizura]

So you think NejiHina would result in 3-headed babies? All kidding aside, the scientific community has COMPLETELY rejected the so-called "scientific" explanation for prohibiting cousin marriages.

The increase in risk is actually not high enough to justify a ban:

The increase in risks is less than double than with non-related parents. Scientists say that it's far from enough to justify a ban. It's just about the same risk as if a woman had a kid at age 40+ instead of before the age 30. Why don't you prevent women over age 40 from having kids? Better yet, prevent drug-takers, smokers, alcoholics and people with a Known family history of genetic problems from having kids. Leave the first cousins alone.

Originally Posted by "Cousin marriages aren't harmful", genetics say - New York Times

Contrary to widely held beliefs and longstanding taboos in America, first cousins can have children together without a great risk of birth defects or genetic disease, scientists are reporting today. They say there is no strong biological reason to discourage cousins from marrying.

First cousins are somewhat more likely than unrelated parents to have a child with a serious birth defect, mental retardation or genetic disease, but their increased risk is nowhere near as large as most people think, the scientists said.

In the general population, the risk that a child will be born with a serious problem like spina bifida or cystic fibrosis is 3 to 4 percent. To that initial risk, first cousins must add an additional 1.7 to 2.8 percentage points, the researchers said.

Although the increase represents a near doubling of the risk, the result is still not considered large enough to discourage people from having children, said Dr. Arno Motulsky, an emeritus professor of medicine and genome sciences at the University of Washington, and the senior author of the report.

``In terms of general risks in life, it's not very high,'' Motulsky said. His report is being published today in the Journal of Genetic Counseling.

He and his colleagues said no one questioned the right of other people to have children, even though they have far higher levels of risk than first cousins. For example, people with Huntington's disease, a severe neurological disorder that comes on in adulthood, have a 50 percent chance of passing the disease to their children.

Motulsky said medical geneticists had known for a long time that there was little or no harm in cousins' marrying and having children. ``Somehow, this hasn't become general knowledge,'' he said, even among doctors.

http://tenets.zoroastrianism.com/cousin33.html

Originally Posted by FindLaw Forum: A genetic report should cause a rethinking of incest laws - cnn.com

Will the new data -- which strongly suggest, for cousins, that the genetic justification does not hold water -- mean that state prohibitions on cousin-marriages are vulnerable to constitutional attack? Certainly, the new data dramatically strengthen the basis for such an attack.

According to the recent report, children of unrelated parents have a 3 percent to 4 percent chance of being born with a serious birth defect. Children of first cousins have only a slighter higher risk--roughly a 4 percent to 7 percent chance. Thus, the ban on cousin marriages will not go very far toward the general problem of preventing birth defects.

http://archives.cnn.com/2002/LAW/04/....incest.04.09/

But the Hyuugas seem inbred, and that increases the risks even more! Um, sorry, you're oversimplifying:

Originally Posted by The straight Dope

All kidding aside, the formerly high incidence of congenital defects, specifically hemophilia, among European royal families isn't the classic demonstration of the perils of inbreeding that everybody thinks it is. The short explanation is that hemophilia is an X-chromosome-related characteristic, transmitted only through the female line. The children of royal female carriers would have been at risk no matter whom their mothers had married.

For more on hemophilia, look here:

http://www.hipusa.com/eTools/webmd/A...iliabasics.htm

Hemophilia is a genetic disease linked to a defective gene on the X chromosome. Chromosomes come in pairs -- women have two X chromosomes while men have one X and one Y chromosome. A woman who has the defective gene is called a "carrier" -- she carries the disease and can pass it to her children, but in most cases, the woman has no symptoms of hemophilia. When a woman who is a carrier has a son, the son receives one X chromosome from his mother, so he has a 50 percent chance of receiving the defective gene (and a 50 percent chance of receiving a normal copy of the gene). Boys who receive the defective gene have hemophilia. Likewise, when a woman who is a carrier has a daughter, the daughter has a 50 percent chance of receiving the defective gene and, thus, being a carrier herself.

So you see, it has nothing to do with cousins. A woman carrier will have a 50% risk of passing on the problem regardless of whom she marries.

Originally Posted by Wikipedia

Some have suggested that the incest taboo is a social mechanism to reduce the chances of congenital birth-defects that can result from inbreeding. Scientists have generally rejected this as an explanation for the incest taboo for two reasons. First, in many societies partners with whom marriage is forbidden and partners with whom marriage is preferred are equally related in genetic terms; the inbreeding argument would not explain the incest taboo in these societies. Second, the inbreeding argument oversimplifies the consequences of inbreeding in a population. Inbreeding leads to an increase in homozygocity, that is, the same allele at the same locus on both members of a chromosome pair. This occurs because close relatives are more likely to share more alleles than nonrelated individuals. If an individual has an allele linked to a congenital birth defect, it is likely that close relatives also have this allele; a homozygote would express the congenital birth defect. If an individual does not have such an allele, a homozygote would be healthy. Thus, the frequency of a defect-carrying gene in a population may go up, or down, when inbreeding occurs.

Thus, in small populations this dynamic would lead to an initial increase in birth defects. But if health care is limited, it is likely that such children would not reproduce; consequently, the frequencies for the allele in question would go down. Ultimately the result would be a population with a large number of homozygotes and a small number of birth defects.

http://en.wikipedia.org/wiki/Incest

In the shinobi world, natural selection would apply, leading to the above. Not only that, the Hyuugas seem genetically healthy, else their clan wouldn't be looked up to as much. So if there aren't any bad genes floating around, there'd be nothing bad to pass on.

Bah, if they're closely related, they won't like each other anyway. Huh?:

Hey, tell that to all the people in the world who have married their cousins. They seem quite happy. And weirdly enough...

Originally Posted by wikipedia

Recent research on the mechanisms of human adaptive immunity suggests that there is a strong evolutionary pressure to maintain as diverse an array of antibody genes as possible. This may provide a biological explanation as to why opposite-sex siblings tend not to be attracted to one another and generally prefer to seek other partners. There is some observational evidence for this: in what is now a key study of the Westermarck effect, the anthropologist Melford E. Spiro, in a cohort study of children raised as communal siblings in the Kiryat Yedidim kibbutz in the 1960s, found practically no intermarriage between his subjects as adults despite pressure from parents and community. The immunoselective theory, however, does not account for the converse phenomenon (dubbed genetic sexual attraction) in which close genetic relatives growing up separately in adoptive arrangements have been observed to become strongly attracted to each other upon reunion.

*shrugs*

So really. We're not telling you to marry Your first cousin. But the genetic argument holds NO ground. Neither does the social one actually, as many societies have nothing against first cousin marriages. In the Bible, there are even instances of God Commanding first cousins to marry. So hold your social prejudices if you want to, but they'd just be that: social prejudices with no scientific base.