A recent study published in the journal Evolutionary Psychological Science examined cooperative and conflictual aspects of affinal relationships (i.e., relationships with in-laws). The results revealed that both men and women report more conflict with their mothers-in-law, than mothers, and that mothers report more conflict with their daughters-in-law, than daughters. Forming lasting relationships with the kin of long-term mates facilitates bonds and investment in offspring by both sexes. Despite the numerous benefits of affinal relationships, conflict is also a central feature. Hamilton’s rul…