Disagree. A brother and sister are more likely than two strangers out of the general population to carry the same recessive genes. For instance, both my brother and I have flat feet, though neither of our parents do. We appear to have both gotten their recessive genes for flat feet, which were then expressed in both of us. Should we marry and have kids (ew, that's a digusting thought), they would almost certainly have flat feet. Now, flat feet are a small burden to bear, but there are many more harmful recessive genes that carry heavy burdens. I don't think it's fair or right for children to be put at an elevated risk of physical harm.
If you are a professional biologist and can scientifically support your statement that the children of an incestuous union would be at NO more risk than the general population of birth defects, etc., then I am willing to be corrected.
Are YOU a professional biologist?
If not, why do you require that qualification of me?
As to the chances, read this:
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.
In large populations with good health care, however, it is likely that there will be consistently high levels of heterozygosity despite periodic inbreeding.
Consequently the alleles linked to congenital birth defects will remain in the population, with a significant chance of a homozygote with the linked allele.
And another thing (boy, you've really got me going here!): If you accept incestuous relationships as a "norm," then they WILL be "accepted practice," and you'll have two- and three-generation streaks of incest -- which will produce a royal genetic mess.
You actually quoted me and then ignored my statement..
In other words, it has to be more than a "singular" occurance within a familial group, it has to be an accepted practice.
I DID NOT "accept incestuous relationships as a "norm"..
I SPECIFICALLY STATED: "singular occurance"..
This translates as: "exception to the norm"..
Was this antagonistic response some sort justification to attack me for daring to disagree with you?
Are you somehow offended when someone disagrees with you?