Oddities Week: Consanguinity and Inbreeding

We call it "inbreeding" and physicians often refer to children with defects by asking if the parents have consanguinity - or are closely related.

A table shows relationships and the rate at which their offspring might be given similar genes that create the defects -
Typical inbreeding coefficient percentages are as follows, assuming no previous inbreeding between any parents:

• Father/daughter, mother/son or brother/sister → 25% (¹⁄₄)
• Grandfather/granddaughter or grandmother/grandson → 12.5% (¹⁄₈)
• Half-brother/half-sister → 12.5% (¹⁄₈)
• Uncle/niece or aunt/nephew → 12.5% (¹⁄₈)
• Great-grandfather/great-granddaughter or great-grandmother/great-grandson → 6.25% (¹⁄₁₆)
• Half-uncle/niece or half-aunt/nephew → 6.25% (¹⁄₁₆)
• First cousins → 6.25% (¹⁄₁₆)
• First cousins once removed or half-first cousins → 3.125% (¹⁄₃₂)
• Second cousins or first cousins twice removed → 1.56% (¹⁄₆₄)
• Second cousins once removed or half-second cousins → 0.78% (¹⁄₁₂₈)
• Third cousins or second cousins twice removed → 0.39% (¹⁄₂₅₆)
• Third cousins once removed or half-third cousins → 0.20% (¹⁄₅₁₂)

What we look for in our breeding population is diversity and if two parents are so closely related that they carry the same gene for disease, there is a guarantee the child will have this difficulty. There is increased risk of birth defects, , facial defects, mental difficulties, weak immune systems, as well. Certainly, this doesn't even cover the social implications of dipping into one's family pool to breed. That's a whole different can of worms.

Famous folks who married their cousins:  HG Wells, Thomas Jefferson, Johan Sebastian Bach, Franklin Roosevelt, Jesse James, Albert Einstein, Charles Darwin (ironically), Edgar Allen Poe, Jerry Lee Lewis, Rudy Guliani.  Considering the millions and even billions of choices on the earth, it seems to me that someone marrying their cousin is just freaking lazy.

Now, let's move on to the horror -