King of the castle (best seen at larger sizes).
Boys climbing on a piece of dead coral at low tide, Kitava Island, Trobriand Islands, PNG
As a follow up to a previous post ( http://goo.gl/zGy7L ), there is an interesting explanation of how the young girls can be sexually active, but have very low pregnancy rates. It all has to do with yams. It is almost impossible to overestimate the importance of yams to the Trobriand culture, and the production of yams is a focus of daily life. A lot of time and energy is spent growing yams, celebrating the harvest, and storing yams. Yams are a source of both food and wealth, and yams are a medium of exchange. Yams are grown by men who spend tremendous effort on growing their yam gardens, not for themselves, but to give to women (recall that this is a matrilineal society). Once the yams are harvested they are displayed for all to see before they are turned over to the woman they have been grown for.
Yams and marriage are significantly linked, and it is only after a man and woman have eaten yams together that they are considered to be married. There are complicated relationships between families centered around the growing and acquisition of yams (too complicated to describe here), and after harvest there are yam festivals and yam competitions, accompanied by much sexuality.
So what does this have to do with pregnancy? It turns out that yams contain phytoestrogens and plant sterols whose effects are contraceptive. The chemist Carl Djerassi synthesized a key ingredient for oral contraceptives (the long-acting progesterone compound norethindrone) from chemicals he extracted from yams in the 1950s, and this research led to the development of birth control pills. So societies that have high yam consumption (including parts of Mexico) experience reduced conception as a side effect. The autobiography that Dr. Djerassi wrote, “The Pill, Pygmy Chimps and Degas’ Horse”, describes the discovery of the birth control pill, and it makes fascinating reading.
More new photos can be seen here: http://goo.gl/47FLK
In answer to comments: yams (Dioscoreaceae, yellow/white colour) and sweet potatoes(Convolvuaceae, orange colour) are often confused in grocery stores, but belong to completely different families of plants.
This large rock is probably a piece of coral rubble that was thrown up into shallow water by a huge storm.