Hawaiian Royalty and Incest

Factual Questions
1

I was reading a book earlier on evolutionary biology (Dr Tatianas sex advice to all creation or something similar) and it made the claim that incest among Hawaiian royalty was (is?) rife and that the offspring of such relationships were treated like gods. The closer the relationship between the parents the better. Two questions spring to mind :

  1. Is this true?

  2. When, and why, did it die out? Assuming it has of course.

2

It’s true:

Hawaiian Royal Incest: A Study in the Sacrificial Origin of Monarchy (.pdf)

Unfortunately, this comprehensive report doesn’t allow text copying, so I can’t quote the relevant passages. But is says that nowadays incestuous marriages are nonexistent.