The half-black, half-latino Armando Muñoz manifested his ability of reactive evolution soon after birth and because of it his mother despised him. He was found by some scientists who experimented on the boy, making his existence known to the public. Moira MacTaggert then took him in as one of her own, and he became a member of the "Missing X-Men" alongside Sway, Petra and Kid Vulcan.

Their mission was to save the original X-Men from Krakoa. Unfortunately, and his teammates Sway and Petra did not manage to survive. So Darwin absorbed them and in their dying efforts Kid Vulcan was saved. But Darwin would not die there and instead he converted himself into energy and fused himself with Kid Vulcan, in a sense giving the entire team a single body. After Vulcan is found many years later he comfronted the X-Men. Marvel Girl sensed that Darwin still resided within Gabriel so she used her telepathic powers to draw him out, which injured Vulcan in the process. The X-Men saw in this their chance of defeating him, but Vulcan was still stronger than they thought and he managed to escape. The crisis past, Beast noticed that Darwin’s remains were still alive, and were starting to restore his body. One week passed and at the Institute’s lab, the Professor and Beast both watched how Darwin’s body restored itself, using nothing but pure energy.

Once fully restored, he was then chosen by Professor X when he led a team to go stop Vulcan from destroying the Shi'ar Empire. When the Professor was captured by agents of the Shi'ar, Darwin secretly jumped on the ship with intent to rescue Professor X. He succeeded only to be recaptured and this rescue attempt failed. Darwin then reluctantly accepted Vulcan's offer to be the Best Man at his wedding.

Darwin (who was completely against the union) attended the wedding, in shackles. Darwin then learned that Professor X was trapped in the M'Kraan Crystal by Vulcan. Darwin feared for his mentor's safety and followed Charles into the depths, eventually succeeding in rescuing him.

Sometime later and back on Earth, the Hulk was responsible for an attack on the Xavier Institute. During his battle with the Hulk, he manifested the ability to absorb gamma radiation but found the Hulk had more then he could siphon off. With this, his body involuntarily decided the best way to defeat the Hulk was to stay away from him and he was teleported out of the battle, and was thought missing for a time.

Darwin has recently returned in the Messiah CompleX storyline fighting alongside the X-Men against various teams also seeking the mutant child.

He will soon be joining X-Factor along with Longshot.

Powers

Darwin's power of reactive evolution means his body will manifest whatever ability it feels is needed to ensure his survival.

Examples of such manifestations include receiving functioning gills after being submerged in water, gaining night vision after being in the dark for several seconds, being able to survive without oxygen when in space, his skin becoming fire-proof when it is exposed to flames, his body becoming pure energy, his intelligence increasing itself or the understanding of the Shi'ar language by looking at it in written form.

However his powers do not always take the effect he desires as during his fight with the Hulk his body teleported him away from the battle rather than supplying a power that would allow him to defeat the Hulk.