In some societies, collective harmony is more highly valued than self-expression. If people are reluctant to speak out, prior culture is more likely to persist unchallenged. Caring deeply about social approval amplifies fears of ostracism and motivates quiet conformity. Moreover, where self-assertion is strongly disliked, feminist activism is more likely to trigger patriarchal backlash. This is a hugely important, but widely overlooked driver of ‘the Great Gender Divergence’.