Original
At least 110 different mutations on at least 6 genes have been identified which may cause too much uptake of iron. The mutations first occurred more than 5,000 years ago. It might be an adaptation from nature to protect against the cold in the north or as some kind of warrior mechanism so people could tolerate to bleed more often. The researchers have over many years speculated over several theories.
The mutations mostly are inherited as autosomal recessive, meaning that you inherit the mutation ion the gene from both parents. Some rare cases of HH could be inherited as a dominant pass on, meaning that it is enough to get the mutation from one of the parents.