At the moment the San people are the presumptive ancestors of us all (non-Africans). To get from there to the blue-eyed platinum blondes in the far North they must be considered to be highly adaptive.
That's why its not surprising to find the Islanders don't look all that much like the guys on the Continent.
I just found an article which states that similarities between Andamanese and African "pygmoid" groups (which I suspect means Bushmen, but perhaps includes others) are convergent. I.e. they evolved independently in distantly related populations. Maybe hair texture is rather easily modified; after all, I didn't take people very long to breed all kinds of strange hair textures in dogs.
The article also found that " New data sets...confirm the absence of any Andaman M2 haplotypes among the ethnic populations of India."
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=378623
One website about the Andamans alleges that female images from Europe thought to be tens of thousands of years old, like the "Venus of Willendorf," show features like steatopygia and peppercorn hair, like Andamanese and Sanids, and suggests that the first populations "out of Africa" had those traits, and therefore that the Andamanese may be a relic of the oldest settlers of much of the world.
Their culture is extremely primitive, being hunting-gathering. They can't even make fire, but carry around something already burning (e.g. ignited by lightning strikes).