Medieval text family trees suggest 60% of works vanished over centuries

For every King Arthur or Roland, whose adventures readers can still enjoy today, another hero of ancient literature may have been lost forever. Before the printing press, texts were copied manually. This process introduced errors and innovations. Like mutations in the replication of DNA, these manuscript changes can be used to create evolutionary trees that philologists call stemmata. Since these trees are based on the extant copies, they do not reflect the full evolutionary history of texts and cannot account for those that are completely lost.