Dating a cousin by marriage
The fuller prohibition has come partly from a desire to keep as far as possible away from something that is spoken of with such serious warning in scripture. As our society has become more numerous and diverse, it has become more repulsive to us to marry close to family. Cousins usually share a common set of grandparents (though it can be only one grandparent) and one-half of the genetic pool.
For example, groups that commonly practiced intermarriage between relatives, like the British monarchy, had children with all sorts of nasty genetic problems.Marrying a cousin is usually considered a bad idea, because inbreeding can lead to harmful genetic conditions.But paradoxically, in some societies, marrying a related spouse is linked to having more surviving children, research suggests.Third cousins usually share a set of great-great-grandparents and one-eighth of the genetic pool.However, your child will only have one-half of your genetic pool and would only share one-sixteenth of the genetic pool with your third cousin. Many people who grow up in the same area probably have this much connection with their spouses and do not even know it.In fact, some combination of these explanations is likely, the researchers said.
Still, it's hard to untangle whether there's a causal link between inbreeding and producing more children, Bailey said.
Keeping it in the family There could be many explanations for the different effects of inbreeding shown in the two kinds of societies.
Perhaps the best explanation, Bailey said, may be that non-foraging societies are more likely to have heritable resources, such as wealth or livestock, so a tight-knit family group might be more likely to defend each other and their shared resources.
And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness, and she see his nakedness; it is a wicked thing; and they shall be cut off in the sight of their people: he hath uncovered his sister's nakedness; he shall bear his iniquity. They include father, mother, step-mother, sister, step-sister, grandchildren, aunt, uncle, daughter in law, and sister in law.
Technically, this does not prohibit marriage to cousins.
Furthermore, the more family intermarriage in a society, the greater the benefit of intermarrying on the number of children couples had.