In pre-colonial Australia, population numbers were so low, a lot of groups had to invent marriage laws to preserve genetic diversity. There are various “skin grouping systems” (it’s nothing to do with the colour of your skin) that say who you can marry, and the systems are designed to minimise cousin fucking and make you go travel to find a spouse so your clan will have plenty of fresh new genes and take good care of the old ones.

First Australians had a better understanding of genetics than European royals thousands of years ago.