For those who have not completed games in the Xenoblade Chronicles series, this page contains spoilers regarding the plot. Discretion is advised.
Humans are a race of beings that are indigenous to the planet Earth and the main playable race in Xenoblade Chronicles X. By the year 2054, Earth had a population of 10 billion humans. However, Earth was attacked and destroyed in a war between two alien races, forcing the humans to evacuate and eventually settle on the planet Mira. They currently reside in New Los Angeles.
DLC Playable Humans
The player eventually learns that all the humans in New Los Angeles are Mimeosomes. These are controlled by their respective humans' consciousness, but the genetic data and actual bodies are housed in Central Life, a supercomputer that was separated from the White Whale when it crashed. One of BLADE's objectives is to find Central Life and revive the actual human bodies before the Mimeosomes run out of power, lest the people of New Los Angeles die.
Humans are descendants of a race known as the Samaarians. The Samaarians were responsible for creating the Ganglion as a race to serve them. Because they were aware of the risk of the Ganglion growing out of control, they made the Ganglion vulnerable to human DNA. Contact with significant amounts of human DNA can destroy a Ganglion. It is because of this that the Ganglion are actively seeking to destroy humanity, the biggest threat to their existence.
In Xenoblade Chronicles 2
In the final chapter of Xenoblade Chronicles 2, it is revealed that humans were originally a race that existed before the creation of Alrest. It is shown that humans once had a successful civilization, having built cities and even space stations, however humans would eventually find themselves in conflict with one another. During this conflict, Klaus, a scientist working on the First Low Orbit Station, used the Conduit to create a new universe after losing faith in humanity. This experiment was ultimately successful, but the Conduit also sent much of the world, including half of Klaus, into different dimensions. As such, humanity suffered great losses and would eventually die off, leaving Klaus and the Guldos the sole remaining humans alive, though the immortal Guldos would become less recognizably human over time. Feeling guilty over his actions, Klaus created the world of Alrest and new life to inhabit it; this life would eventually become the human subraces that would call the world of Alrest their home, such as the Ardainians, Gormotti, Indoline, Leftherians, Tantalese and Urayans.