Guns, Germs, and Steel: The Fates of Human Societies
What does Diamond say about language pockets in Asia according to Guns, Germs, and Steel?
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From the text:
Austronesian languages reached the Asian mainland on the Malay Peninsula and in small pockets in Vietnam and Cambodia, near the westernmost Indonesian islands of Sumatra and Borneo, but they occur nowhere else on the mainland.
Guns, Germs, and Steel: The Fates of Human Societies