- "We possess no age. We were built this way. In time, we will receive souls. Then our bodies will begin to grow."
- —A Genome
According to the Final Fantasy IX Ultimania, Garland began creating Genomes roughly 3000 years prior to the game's beginning to act as vessels for the Terran souls so that Terra's civilization could one day be revived. Terra was an ancient planet whose civilization attempted to save itself by fusing it with a younger planet.
The Fusion between Terra and Gaia was a failure. The Terran people gave up their physical bodies and laid themselves to rest, placing the burden of salvation on Garland. Garland created the artificial race of Genomes, to inherit the souls of Terra once the Fusion was complete.
Due to the nature of their creation, the majority of the Genome population lack a soul, and have little to no emotional response; Genomes are nothing more than empty husks awaiting the attainment of a soul. A Genome does not begin their life as a baby but are created as they appear in the game. The Genomes of Terra frequently mention through player interaction that their existence is perpetually incomplete until they receive a soul. As such, the collective Genome existence is dedicated to the preparation of attaining a soul, mentally and physically.
The Genomes also seem to know a great deal of the Soul Cycle and the world in which they live. Although this knowledge is useless to a vessel who will soon forget what they have learned upon receiving a soul (as stated in the game), information is circulated among the population to prevent mental decay.
The Genomes of Terra harbor production facilities (although the only one the player is informed of resides in Bran Bal) in which they create more of their race. Through these production facilities, they aim to create a more suitable vessel for a soul to reside in. This could also be interpreted as somewhat recreational due to their seemingly meaningless existence.
Garland created Kuja and Zidane Tribal with hopes of restoring the whole of Terra's population. He deemed Kuja an inferior Genome after observing flaws and weaknesses that Zidane lacked, and placed his hopes into him instead, as he saw Zidane as "The Perfect Genome".
He later created Mikoto, the third Genome to be instilled with a soul directly by Garland. She was to assist him in creating a superior genus of Genomes and to take Zidane's place were he to fail.
Zidane does not learn of his identity as a Genome until he and the party travels through the Shimmering Island to Terra. There, Mikoto leads the otherworlders to Bran Bal, the village of Genomes. Zidane and his companions are shocked to discover that the Genomes look exactly like him.
However, all the Genomes, save Mikoto, are unresponsive, and Zidane asks Mikoto about their true nature. Mikoto's explanations serve only to send Zidane into a brooding state, unsure of his exact nature. Later, Garland appears before Zidane and reveals his entire plan for Gaia, Terra, Genomes, and his trio of Angels of Death.
After escaping Kuja's destruction of Terra on the Invincible, the party leaves the Genome survivors with the black mages, where they live for the remainder of the game. What becomes of the Genomes afterwards is uncertain.
In science, a genome is "the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA".