These findings revolutionize the understanding of the prehistory of the island, until now believed to have remained uninhabited until the arrival of peoples of Austronesian stock some 1500 years ago (with some scattered evidence of earlier inhabitation but nothing too conclusive). New archaeological data pushes back the first colonization period to some 4000 years ago, a time when Malayo-Polynesian culture was still restricted to, roughly, the Philippine archipelago.
Robert E. Deward et al., Stone tools and foraging in northern Madagascar challenge Holocene extinction models. PNAS 2013. Pay per view (6-month embargo) → LINK [doi:10.1073/pnas.1306100110]
Past research on Madagascar indicates that village communities were established about AD 500 by people of both Indonesian and East African heritage. Evidence of earlier visits is scattered and contentious. Recent archaeological excavations in northern Madagascar provide evidence of occupational sites with microlithic stone technologies related to foraging for forest and coastal resources. A forager occupation of one site dates to earlier than 2000 B.C., doubling the length of Madagascar’s known occupational history, and thus the time during which people exploited Madagascar’s environments. We detail stratigraphy, chronology, and artifacts from two rock shelters. Ambohiposa near Iharana (Vohémar) on the northeast coast, yielded a stratified assemblage with small flakes, microblades, and retouched crescentic and trapezoidal tools, probably projectile elements, made on cherts and obsidian, some brought more that 200 km. 14C dates are contemporary with the earliest villages. No food remains are preserved. Lakaton’i Anja near Antsiranana in the north yielded several stratified assemblages. The latest assemblage is well dated to A.D. 1050–1350, by 14C and optically stimulated luminescence dating and pottery imported from the Near East and China. Below is a series of stratified assemblages similar to Ambohiposa. 14C and optically stimulated luminescence dates indicate occupation from at least 2000 B.C. Faunal remains indicate a foraging pattern. Our evidence shows that foragers with a microlithic technology were active in Madagascar long before the arrival of farmers and herders and before many Late Holocene faunal extinctions. The differing effects of historically distinct economies must be identified and understood to reconstruct Holocene histories of human environmental impact.
Notice that this colonization is also older than the Bantu expansion and therefore these settlers must have been pre-Bantu peoples of East African roots.
The sites are located in the North tip of the island, what is consistent with arrival through Comoros, the most natural route between East Africa and Madagascar, which requires the sailing of some 190 miles (~350 Km) of open sea.
Otherwise the narrowest extent of the Mozambique Channel, between Angoche and Tambohorano, is of some 460 Km. The small island or Juan de Nova (uninhabited except for a military garrison) lies to the south of this other potential sailing route.
The toolkit found in the key site of Lakaton'i Anja includes many microliths, as well as some larger tools, made of chert and obsidian. This last must have been brought from far away, as there are no sources of the volcanic glass in Northern Madagascar.
An important point is that these new dates show that human inhabitation did not kill the Malagasy megafauna right away but that instead humans and giant animals shared the environment without immediate catastrophic consequences, which would only happen in the last two millennia.
Partial source: Rhett A. Buttler, Madagascar occupied by humans 2,500 years earlier than previously thought, Wild Madagascar (via Pileta).