[A. Pole]

Generally speaking when a more advanced society moves in and takes over the guys that are already there are reduced in number and the females become the property of the migrating males.

No, it is rather a fluke caused by the one sex inheritance of Y chromosome (or mitochondria in case of women). To transmit Y chr. you need to have uninterrupted succession of male descendents - you get only daughters and your Y is gone (even if your other genes pass through). To transmit mitochondrial genetic material you need to have uninterrupted succession of women.

So after number of generations you have one prevailing mitochondrial female ancestor and one prevailing Y male ancestor (in two different places and generations).

[Harmless Teddy Bear]

To transmit Y chr. you need to have uninterrupted succession of male descendents - you get only daughters and your Y is gone (even if your other genes pass through).

Granted. But it would be a bit unusual for that to happen with one of the natives to this extent and not with those who migrated in who would have had superior numbers as a general rule.