Malagasy ancestry reflects a blend of Austronesian (Southeast Asian) and Bantu (East African) roots. The settlement of Madagascar is a subject of ongoing research and debate. Archaeological finds such as cut marks on bones found in the northwest and stone tools in the northeast indicate that Madagascar was visited by foragers around 2000 BC. Traditionally, archaeologists have estimated that the earliest settlers arrived in successive waves throughout the period between 350 BC and 550 AD, while others are cautious about dates earlier than 250 AD. In either case, these dates make Madagascar one of the last major landmasses on Earth to be settled by humans. Early settlers arrived in outrigger canoes from southern Borneo. Upon arrival, early settlers practiced slash-and-burn agriculture to clear the coastal rainforests for cultivation. The first settlers encountered Madagascar's abundance of megafauna, including giant lemurs, elephant birds, giant fossa and the Malagasy hippopotamus, which have since become extinct due to hunting and habitat destruction. By 600 AD groups of these early settlers had begun clearing the forests of the central highlands. Arab traders first reached the island between the seventh and ninth centuries. A wave of Bantu-speaking migrants from southeastern Africa arrived around 1000 AD. They introduced the zebu, a type of long-horned humped cattle, which they kept in large herds.
By 1600, irrigated paddy fields were developed in the central highland Betsileo Kingdom, and were extended with terraced paddies throughout the neighboring Kingdom of Imerina a century later. The rising intensity of land cultivation and the ever-increasing demand for zebu pasturage had largely transformed the central highlands from a forest ecosystem to grassland by the 17th century. The oral histories of the Merina people, who may have arrived in the central highlands between 600 and 1000 years ago, describe encountering an established population they called the Vazimba. Probably the descendants of an earlier and less technologically advanced Austronesian settlement wave, the Vazimba were assimilated or expelled from the highlands by the Merina kings Andriamanelo, Ralambo and Andrianjaka in the 16th and early 17th centuries. Today, the spirits of the Vazimba are revered as tompontany (ancestral masters of the land) by many traditional Malagasy communities.