If it’s true that Iceland is basically a “closed country” in that natives only marry other natives, etc., it’s just a matter of time until Icelanders become so inbred that, like the Amish and other “closed” societies, they start to experience 6-finger dwarfism, mentally handicapped children, etc.
If the “closed country” causes defects and mentally handicapped children, how did mankind or any other species ever flourish? I am thinking that there are plenty of Icelanders in that country to marry and have diversity of DNA, and something is wrong the the theory of evolution.