Where do you live? Country?

It's common in basically the whole Arab world.

https://en.m.wikipedia.org/wiki/Cousin_marriage_in_the_Middl...

Common in Pakistan, also - not sure about India.

It’s odd, because Islam preaches ‘bodily purity’ but repeated cousin marriage rapidly causes the accumulation of significant genetic defects - so you’d think religion would steer culture towards better beliefs and practices concerning that.

I think you’re confusing religion with cultural practices. Islam allows cousin marriage, but doesn’t encourage it.

Yeah, my post was ambiguous - I was wondering why people who followed Islam retained a cultural practice which seems at odds with the religious principles of physical and ritual purity.

> so you’d think religion would steer culture towards better beliefs and practices concerning that.

If we were to take into account what would influence a family to practice marriage between cousins in excess (which is largely a preoccupation with material wealth and status), then it does.

What drives it? Wealth retention to keep it in the family?