"1280 people" is just a misleading simplification early in the linked article. Both the news article and the original paper speak of 1280 breeding individuals.

"1280 people" is just a misleading simplification early in the linked article. Both the news article and the original paper speak of 1280 breeding individuals. Also, the way population dynamics work, lineages tend to die out quickly or not at all. Isolated populations can die out gradually, but it takes exceptional circumstances for a population to survive in the long term while remaining isolated.