First paragraph (this article has no abstract)

In human genetics, the equivalent of finding gold mine is finding a genetically isolated population with excellent medical records. Inbreeding often magnifies the effects of single gene traits because homozygosity is more common, and a society in which family medical histories can be traced back for many generations allows patterns of inheritance to be ascertained with confidence. Given the mobility of the human population today, such societies have become rare, but they do exist. There was a lot of excitement in the early 1990s about genetic studies of Mormon communities in Utah in the USA, and they have provided useful information. So have French Canadian communities in eastern Canada and some groups in rural India. But the society that attracted the most attention - and the program that has created the most controversy - is that of Iceland.