|MadSci Network: Genetics|
As far as I can tell, the "problem" with inbreeding is not that is causes bad genes to appear, but it keeps them in the gene pool. This is also true of good genes, but then bad genes are more likely to occur through natural mutation. Let's take the example of a small tribe. Without extensive medical facilities, dominant gene mutations which cause severe medical conditions will cause death before reproduction. From an evolutionary perspective, this does not have an adverse effect on the gene pool. However, a recessive mutation will not be wiped out so easily. A recessive gene can hang around in the gene pool for a long time before being expressed as a disease. All of a sudden, the entire tribe becomes homozygous for a gene which causes a problem.
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