Star Trek: 10 Alien Species That Are Actually Related
6. Ba'ul And Kelpiens
The Ba'ul and the Kelpiens evolved together on the planet Kaminar, where they shared a very complicated predator/prey relationship.
Prior to the 1st century, the Ba'ul were hunted by Kelpiens who had undergone the vahar'ai (a metamorphosis that transforms Kelpiens into deadly, fearless warriors). It got so bad for the Ba'ul that their population dropped to less than 260 individuals. They were able to save themselves from extinction by killing all of the post-vahar'ai Kelpiens, and brainwashing the survivors into believing that the the vahar'ai is meant to be the natural end of a Kelpien life, when in fact it is an evolution.
By tricking their former oppressors, the Ba'ul became the predators and the Kelpiens their prey. In the Discovery episode The Sound Of Thunder, their deception was exposed, and the Discovery crew was able to trigger vahar'ai in all of the Kelpiens on the planet. After this revelation, the Ba'ul could no longer dominate the Kelpiens, and they were forced to find a way to coexist.