...about this subject.
One reviewer whines "How Do We Know?" and thereby implies directly that the author is a liar, and made up everything reported in this book.
While that person may choose to remain in darkness, this book was very well received among professionals, who realized at once that it added more detail (a lot more detail) to the generally known facts about sexuality in New Guinea. In fact, there are many other tribes, reported in the literature, who practice the same system of sexuality -- with the perhaps interesting exception that the sexuality is not oral but via the posterior route.
As for disguising the name of the tribe, it seems to me that Herdt has really done something quite remarkable: he has protected his sources. There is no tribe called the "Sambia" in New Guinea, but there is the tribe which Herdt studied, and one of the key elements in their system of male sexuality is that it must be kept SECRET.
In this, I must confess that by the age of 60 I have seen this sort of behavior all over the world: men can have all the sex they want together, but it is imperative not to scare the horses. DON'T let the women know.
If Herdt had published his book with the tribe's real name, he would have blown their cover. I congratulate him for not doing so.
As for what the Sambia are up to, I would suggest reading the book, and not counting on a book review to fill you in on all the details. But as a very high-level view, the Sambia have a superstitious belief that a young boy's development into a full-fledged male is a highly doubtful procedure -- not guaranteed by the spirits or the gods. So they practice "boy invigoration," which entails the young boy receiving regular doses of masculinity. When the boy reaches puberty, the magic has obviously worked, so it is time for him to reverse roles and begin helping the younger ones.
All in all, this is one of the most fascinating books I have ever read. It's true to say, "We're not in Kansas any more, Dorothy." No, we're in the steamy jungle islands of New Guinea and Papua New Guinea, and learning about some of the very flexible limits of human sexuality.
Highest possible recommendation!