An activist whose petition earlier this year triggered a Tanzanian high court ruling against child marriage said social transformation was needed to end the longstanding custom many families use as a “survival system.” “Changing the law is not the ultimate end to child marriage,” said Rebeca Gyumi, founder of the Msichana Initiative, a Tanzanian charity promoting girls’ rights. “Changing mindsets and trying to trigger the shift of customs and traditions is the next thing we are planning...