they are made from a number of trees, including the buttress roots of tropical rain forest trees i believe. i have held an original and they are surprising light (made from light weight wood) the tips are thin, stiff and non working. they are a bend through the handle design and the limbs have a very slightly convexed back, and slightly more convexed belly. the edges of the limbs come down to an almost razors edge. some bows i have a large ridg running down the back of the bow, full length and in the centre. the bows are also not as big as they look in the photos. i think the andaman people are a fairly small race (still living primitively today) which gives the impression they are bigger bows. i am not sure what game animals live on the andaman islands, but i think the bows were used for fishing also. the anaman people were apparantly known as the silent people, you didn't know they were there until you had an arrow through you!
i have made a couple of bows in this design and they are excellent selfbows. i know a prominant australian bowyer who prefers this bow design over any other for selfbows, as they work very well for our australian hardwoods. i don't know the reason for the 'S' shaped design and i haven't put that into mine.
i dont know how to insert images sorry so i can't show pics of mine or one with a ridge down the back.