Around 1000 A.D., Tahitians from the islands of Ra’iatea, Bora Bora, and Huahine arrived in Hawaii. With their larger statures, they easily overpowered the islands’ inhabitants, descendants of Polynesian settlers that had arrived several hundred years prior.
There is still dispute and controversy as to the identity and origin of the first human settlers in the Hawaiian Islands, although most scholars agree, thanks to recent radiocarbon dating, that the initial voyagers sailed from distant islands, known by Polynesians as Kahiki, in the South Pacific, most likely the Marquesas, in the eleventh century A.D.
As the number of new settlers from Polynesia grew, the original inhabitants slipped into servitude. Mary Kawena Pukui believed that the outcast slaves known as kauwā, kept for human sacrifice, may have been the descendants of the earliest people. Kauwā, who were regarded as foul-smelling things, were tattooed on their foreheads and made to hide their heads under pieces of kapa. Like the Untouchables of India, kauwā were scapegoats born into and imprisoned within an abhorred class. Confined to certain districts such as Makeanehu in Kohala, and Kalaemamo in Kona on the Big Island, they were forbidden to marry outside their caste, or even to enter the house or yard of a man who was not kauwā.
There were many interisland conflicts in Hawaii before European or American contact in the islands. There is a topical list at wikipedia;
Another unique aspect of the pre-European contact in Hawaii was the Kapu system. This is a system of religious laws, often considered very strict and at times brutal.