While the world-system was entering a phase of decline during the ninth and tenth centuries, a first Arabo-Swahili advance occurred toward the Comoros and Madagascar, setting up networks in what M. Horton has called the “Swahili corridor.” This push would intensify from the early eleventh century onward. During what is known as the Comorian Dembeni phase, Madagascar underwent changes linked to the arrivals of populations from the East African coast and the Comoros. These were reflected in major ecological changes. While the Austronesians, skilled in combining rice and tuber farming in humid tropical ecosystems, were developing the island’s wettest regions (its northern and eastern coasts), and soon afterwards part of the Highlands, some Bantu-speaking migrants, at an early stage, were occupying other ecosystems, by clearing land in drier regions of the western Malagasy coast. These migrants brought with them African species suited to the conditions in these zones: sorghum (Sorghum bicolor) and two legumes, the cowpea (Vigna unguiculata (L.) Wal.) and the Bambara pea (Vigna subterranea (L.) Verdc.). They also developed extensive animal husbandry: the zebu seems to have been introduced around the ninth century in the northwest, which had repercussions on the plant cover and a subfossil fauna (Burney et al.