Across the universe, black holes are not simply born and then gone — some are veterans of violence, carrying within their spin the memory of past collisions. A team led by MIT's Cailin Plunkett has read the gravitational wave records from LIGO, Virgo, and KAGRA and found that roughly one in seven merging black holes has collided before, their rapid rotation and orbital wobble serving as a kind of cosmic autobiography. This discovery suggests that the most massive black holes may not be singular products of dying stars, but rather the accumulated result of repeated mergers in the densest corner