Michael Cook laments that comparing Ibn Ishaq with the later commentator Al-Waqid — who based his writing on Ibn Ishaq but added much colorful but made-up detail — reveals how oral history can be contaminated by the fiction of storytellers ("qussa"). "We have seen what half a century of story-telling could achieve between Ibn Ishaq and al-Waqidi, at a time when we know that much material had already been committed to writing. What the same processes may have brought about in the century before Ibn Ishaq is something we can only guess at."