What's a cousin to you?

A lot of our culture can be laid at the door of the early medieval church's ban on forms of cousin marriage.

We know this benefits fitness now, but many cultures get away with less fitness for centuries.

For example, a culture of free soloing a 2900 foot cliff might hurt fitness.

In Australia, we can see a multitude of ways to delineate relationships.

For the Kunai and Yuwaaliyaay, all cousins were "brothers" and "sisters". They could not marry.

For the Sandbeach and Minong, distant cross-cousins were preferred for marriage.

In the Ngarinyin and Yolngu, matrilineal cousin marriage was preferred.