Gamilaraay kinship revisited: incidence of recessive disease is dynamically traded-off against benefits of cooperative behaviours

TL;DR

This paper examines the Gamilaraay kinship system and reveals how it balances reducing recessive disease risk with fostering cooperation, demonstrating a dynamic trade-off influenced by relatedness patterns.

Contribution

It provides a formal analysis of how traditional marriage rules in the Gamilaraay system optimize relatedness to balance health and cooperative benefits.

Findings

The Gamilaraay system minimizes recessive disease incidence.

It promotes cooperation through relatedness adjustments.

The system's dynamics are explained via Hamilton's rule.

Abstract

Traditional Indigenous marriage rules have been studied extensively since the mid 1800s. Despite this, they have historically been cast aside as having very little utility. This is, in large part, due to a focus on trying to understand broad-stroke marriage restrictions or how they may evolve. Here, taking the Gamilaraay system as a case study, we instead ask how relatedness may be distributed under such a system. We show, remarkably, that this system dynamically trades off kin avoidance to minimise incidence of recessive diseases against expected levels of cooperation, as understood formally through Hamilton's rule.