spot wrote: That's how you define inbreeding. Inbreeding = closely related genetic inheritance.
Let me try to explain it using short words. Every time I try doing this I get spat at for insulting peoples' intelligence but even so it's worth trying.
Inheriting deleterious traits harms people.
Deleterious traits can be inherited or they can spontaneously appear in a person and be subsequently passed on to the person's children.
If the deleterious trait only needs one parent to pass down it for it to show up physically in their children, then it's called Dominant instead of Recessive. If it's Dominant then the only way it can spread in a population is if some carriers of the trait are immune - like women not suffering from Haemophilia for example, so they can spread it to a new bunch of boy children - or if the child is statistically lucky and doesn't inherit that particular part of the parent's makeup - different diseases have different proportions of children inheriting the trait.
If it's a recessive deleterious trait then it only shows up if both parents are carrying it, and then only in half their children, so it can float around in a population for many generations without being cleaned out by early deaths of the carriers.
The thing about marrying a parent, a parent's sibling, a sibling or a first cousin is that the chance of both new prospective parents carrying a recessive deleterious trait are higher, given that one of them has it, because they're both closely related to an ancestor who was passing it down.
If the family, or the prospective parent, has no recessive deleterious traits then marrying any of them is purely a cultural problem, not a biological one.
If two random people from anywhere on earth both have the same recessive deleterious trait then the effect of their marrying is the same, biologically, as what you describe as "inbreeding" even though they're not closely related.
So - conclusion - with clean family genetics, there's no biological problem in first cousin marriages. With genetic editing, when it arrives, that can fix these diseases whenever they show up, again it's no longer a biological problem. Until then, random mutations will bring the diseases back into existence in every generation - it's where these genetic-inherited diseases come from in the first place - and some marriages will randomly bring two recessive carriers together anyway.
Some recessive deleterious traits (like sickle-cell anaemia) are tested for in some populations to confirm to potential carriers that they are clear to marry if they want. It's a purely cultural taboo that prevents those tests being offered to close relatives like first cousins to give them a go-ahead.
*sigh* :-4
I want your love child too...
