How and why did Riau Indonesian acquire its isolating profile? Its
isolating structure may traced back continuously through a series of increasingly large
language networks – Malay/Indonesian koinés, Malay/Indonesian in general, Malayic,
Western Nusantara, and the Mekong-Mamberamo linguistic area – thereby refuting claims
that it is the product of a recent event of creolisation. Riau Indonesian and its
relatives exhibit dual heritage: Austronesian and Mekong-Mamberamo. From an Austronesian
perspective, the isolating profile developed when Austronesian languages first spread
into Nusantara, as a result of contact with the languages that were already present in
the region. However, from a Mekong-Mamberamo point of view, the isolating structure may
be viewed as the outcome of vertical inheritance dating back as far as we can see.