So apparently agriculture came into a new area with migrating farmers, rather than as a meme, in Southeast Asia as well as in Europe and South Asia. Or so ancient human DNA from Vietnam shows.
This three-pronged mixture of indigenous hunter-gatherers, early farmers, and a later wave of migrants parallels the prehistory of Europe, also illuminated by ancient DNA in recent years. There, migrating farmers brought agriculture from the Near East to Europe, where they mixed with local hunter-gatherers about 7000 years ago. Then later waves of Bronze Age migrants—in Europe’s case, herders from the Central Asian steppe—moved in and established the population structure scientists see today. (Researchers, including Reich, have also documented a similar pattern in South Asia.)
Always thought that was most likely. People will move before they’ll tell neighbours their secrets.