By 1000 BC, the inhabitants of the Philippine archipelago had developed into four distinct kinds of peoples: tribal groups, such as the Aetas, Hanunoo, Ilongots and the Mangyan who depended on hunter-gathering and were concentrated in forests; warrior societies, such as the Isneg and Kalinga who practiced social ranking and ritualized warfare and roamed the plains; the petty plutocracy of the Ifugao Cordillera Highlanders, who occupied the mountain ranges of Luzon; and the harbor principalities of the estuarine civilizations that grew along rivers and seashores while participating in trans-island maritime trade. It was also during the first millennium BC that early metallurgy was said to have reached the archipelagos of maritime Southeast Asia via trade with India