The Zeronites were a genetically engineered ape-like species.
When the Kulkan were more warlike, they built a genetic weapons centre which later became Hippocrates Base. At the centre, they created the Zeronites to maintain their interstellar missiles.
Centuries later, the surviving Zeronites attacked the base to gain revenge on the Kulkan. The Eighth Doctor was able to stop their plans. (COMIC: Sins of the Fathers)