"... At this moment, a strange thing happened — a woman paired off with a warrior and sat on the sand in a passionate embrace. This act was being repeated by other women, each claiming a warrior for herself, a sort of community mating, as it were. Thus did the militant group diminish. This continued for quite some time and when the tempo of this frenzied dance of desire abated, the couples retired into the shade of the jungle....
That is about the tribe in Andaman and Nicobar Islands which hasn't had contact with the outside world for at least thousand years. They are hostile to contact worse our contact might kill them as they aren't immune to disease we are.
The tribe is estimated to have inhabited the island for 60000 years.
Ps: Dont we love Wiki? Oh, thanks Sepia mutiny, some random genetic article link from your space led me to this entry:)