 Notable proponents include William Meacham, Stephen Oppenheimer, and Wilhelm Solheim.For various reasons, they proposed that the homelands of Austronesians were within Island Southeast Asia (ISEA), particularly in the Sundaland landmass drowned during the end of the last glacial period by rising sea levels.Stephen Oppenheimer's studies on Southeast Asian and Pacific genetics, in particular, focused on the discovery of a mitochondrial DNA (mtDNA) haplogroup that have been evolving in the Indonesian archipelago for more than 40,000 years.