Is it really biologically unsafe for cousins to have children?

Question

i've heard many times that when people people that are closely related have children, they have greater chances of birth defects. however, throughout history, many of the greatest dynasties and monarchies have kept power in the family by intermarrying and interbreeding. so is it really okay for people that are related to have children, or is this simply something that society tells us is wrong, with no valid reasoning to back it up?

by the way, i'm not going to be marrying a cousin or anything, i was just wondering.

Answer 1

Mina is right. It is because cousins have a chance that their blood is the same type as your own and is similar that causes birth defects. Although i do tend to think about it myself as Gypsies and Travellers marry their cousins

Answer 2

Just like physical traits, the incidence of birth defects in members further from each other on branches of the family tree is heavily diluted. First cousins born of siblings may be more at risk of developmental problems than that of third or fourth cousins, or those born of third or fourth cousins themselves... if that makes sense.

Answer 3

i no sum 1 who's parents are first cousin sand have had 12 kids who have all turned out absolutely normal  

Answer 4

back then, the world's population was less and people's blood were purer, free of diseases. as the world population grows and more diseases are discovered, the risk of birth defects between relations increase.

Answer 5

think about it this way. Down syndrome is a recessive gene. and you have a heterozygous dominant gene. that means if you make a baby with your cousin, your baby has a 75% chance of having down syndrome.  

Answer 6

Yes, it IS unsafe for cousins to have kids

You're right in pointing out that many of the dynasties have kept power through inbreeding, but it has come to backfire on them. The entire Hapsburg Dynasty heirs became hemophiliacs because the gene stayed in the family. Royal families often had 10 kids not because they wanted to, but because they HAD to because their heirs kept dying of inherited diseases like hemophilia.

it works like this....say your grandmother was a carrier for a disease but didnt develop it, and instead passed down the carrier gene to her kids, who passed it on to their kids (you, your siblings and your 1st cousins)

since you and your cousin share the same grandparents, then its likely that BOTH of you have that gene for the disease, and if both are carriers, that its extremely likely that your kids will have the disease