Humans

The humans (人間 ningen), also known as the Ancients, were the original humans in the Mega Man Legends series. Sometime before or after an unknown disaster covered the world in endless water, the humans all died out. Their human presence was replaced on Terra with the artificially created human life forms known as Carbons. The only original human that is seen in the Mega Man Legends series is The Master—being the sole surviving human after thousands of years living on the Heaven-like world of Elysium. After The Master perishes, there are no living original humans left on Terra or Elysium, leaving behind only their genetic codes in the library of Elysium. However, after The Master died, Mega Man came into possession of his Genetic Code.

History
Thousands of years after an unknown apocalyptic event that occurred on Terra (or the Earth in the Japanese version), the humans (also known as the Ancients by the time of the main events of the Mega Man Legends series) have all died off. Terra is repopulated by a new form of human life—the Carbons, which are an artificially created version of humans—and The Master System is designed to monitor and watch the world. After the humans vanished only one man remained—The Master, who has lived more than 3,000 years on the artificial world of Elysium. After modifying the "betas" (Carbons) slightly, The Master asks the Purifier Unit, Mega Man Trigger, to take him to Terra in order to observe the way that the Carbons live out their lives. After reaching the conclusion that he never truly felt happy in Elysium, he requests that Mega Man Trigger destroy the Master System. He then gives Mega Man Trigger his genetic code to facilitate his mission. Unable to survive long outside of Elysium, The Master dies soon afterwards, bringing humankind to extinction.

However, The Master System was programmed with a contingency plan in the event that The Master died and humans became extinct in the form of the Carbon Reinitialization Program, which would purge all the Carbons and produce new humans from the genetic data stored in the Elysium Library.

Mega Man Trigger attempts to shut down the Master System as The Master had requested. He disobeyed the system, and as a result of this, needed to confront the Mother Unit, Sera, which led to a decisive battle that left both of them sealed away for thousands of years.

After being found by Barrel Caskett on Terra and living out a new life as Mega Man Volnutt, he eventually comes to remember his past and once again attempt to shut down the Master System by confronting and doing battle with the awakened Sera once more, this time succeeding and stopping the Master System and The Carbon Reinitialization program once and for all.

This stops the genetic code of the original humans from ever being re-implemented into Terra and keeping them from returning. Theoretically, this would have ended the original human race.