[pigscantfly]

Linguistic displacement can occur without genetic displacement. This has happened many times in history -- usually when a society's elite are displaced by a linguistically distinct foreign elite and their language is gradually adopted down the ranks of society as people seek advancement. Many branches of Proto-Indo-European (eg. Anatolian) are thought to have spread in this manner ie. with elite but not whole-population displacement.

I wasn't aware of this Australian language family example, but it may not be as surprising as it sounds at first.

[WalterBright]

That happened in England after the Battle of Hastings. Upper crust English is still dominated by french words.

[jjtheblunt]

My Germanic Linguistics grad school prof told us once, to your point, if you count etymologies of words in spoken English and in the English dictionary, you'd get roughly the following: spoken English uses roughly 80% Germanic vocabulary, but the English dictionary is roughly 80% Latin and Greek words (anglicized).

[WalterBright]

I've heard it put more crassly as "barbarian grammar with french nouns"

[codebje]

The only thing that got hacked to pieces more than the English peasantry during the middle ages was the English language.

[jjtheblunt]

That's great.

[runsWphotons]

This is true but is also something there would be reason to doubt in Australian context. It seems more likely that peoples in northern australia had some contact with outsiders around the time discussed in article, got some technological advances and small degree of genetic mixing from absorbing the outsiders, and then spread out, probably helped by some new techniques. But this is just one conjecture.