  The practice of marriage is an understudied phenomenon in behavioural
sciences despite being ubiquitous across human cultures. This modelling paper
shows that replacing distant direct kin with in-laws increases the
interconnectedness of the family social network graph, which allows more
cooperative and larger groups. In this framing, marriage can be seen as a
social technology that reduces free-riding within collaborative group. This
approach offers a solution to the puzzle of why our species has this particular
form of regulating mating behaviour, uniquely among pair-bonded animals.
