You may also be looking for "Atavus" the episode.

The Atavus are an ancient humanoid species that lived on Earth some three million years before humans evolved. Both the Taelons and the Jaridians evolved from the Atavus. For reasons unclear, the Atavus living on Earth were forced to retreat into stasis in "hives" hidden around the planet. Those on other worlds eventually split into the Taelons and Jaridians; prior to this separation, the Atavus either evolved or were granted the shaquarava, distinguishing themselves from their energy claw-wielding forebears.

Both the Taelons and the Jaridians seem to have forgotten the nature of the original Atavus, since whenever one of those species "reverts" to an Atavus, they revert to a bestial Taelon/Jaridian with a shaquarava. When a Taelon is exposed to Jaridian energy, or tries to merge with a Jaridian, he can revert to an atavistic state as Da'an did when he tried to merge with Balvak ("The Summit").