Mutants (also known as Homo Superiors) are people who posses the X-Gene and developed superhuman powers, traits, and abilities. These powers range from physical to psychic or psionic based. The mutant gene can also cause physical traits and characteristics no humans possess, commonly having the skin or eyes more animal-like than human. Any such attributes are not always controlled by the mutant in question, as some cannot control their powers properly or at all, especially if their mutation affects their appearance. The mutant gene usually manifests at puberty, often at times of great stress, while some mutants, like Sabertooth and Wolverine, could develop it beforehand if they also experience such levels of stress. According to Pyro (from the second film), it's been discovered that males (human or mutant) carry the mutant gene and pass it on. As such, female mutants can't pass the gene to their offspring.
The first mutant appeared during ancient Egypt thousands of years ago. James Howlett and Victor Creed, whom fought in important wars of American history, were the next, earliest known mutants. By the time of World War II, mutants became a more widespread phenomenon, though humanity at large continued to be ignorant of their existence. Alternatively, the Nuclear Age caused an acceleration of the mutant gene, finally making a species of them.
It was not until 1960's when the existence of mutantkind was revealed during the Cuban Missile Crisis, which was orchestrated by Sebastian Shaw, who sought to destroy baseline humans so that mutants could rule the Earth, with Shaw as their leader. His plans were thwarted by a group of mutant misfits, whom used their unique gifts to prevent a nuclear war, effects of which would cause the mutant gene to become truly dominant on the planet, with humanity becoming extinct as a result. However, their heroic actions exposed mutants to the world in irrevocable ways.
First Extermination Attempt
In 2003 Colonel William Stryker, Jr. sought to rid the world of mutantkind by using a combination of his son, Jason, and Charles Xavier's powers with Cerebro to mentally kill all mutants in the world. His plan nearly backfired at him and not only nearly caused homo sapiens' extermination, but also a full-out war between mutants and humans.
A "Cure" to mutation
The billionaire businessman Warren Worthington II sought to cure his son of his "alignment" and used his corporation to create a mutant cure, using a mutant child as a source. The cure was supposed to be used to cure mutants and make them human again, but it was also used as a weapon by USA military in case dangerous mutants posed a threat to human lives.
Learning of this mutant supremacist, Magneto led an army to the headquarters of Worthington Labs, in San Francisco, to destroy it before it was used to exterminate mutantkind. He was thwarted by the X-Men, fortunately
In 1973, the Sentinel Program was used after Bolivar Trask was killed by Mystique. Later on, with her DNA, they create the Sentinel Mark V, a Sentinel that can adapt to its environment. With these, the Sentinels take over the world, exterminating mutants, those with the mutant gene, and those that supported mutant resistance, thus leaving the worst of mankind left. Few survive. This however was fixed when Wolverine is sent back in time and was able to successfully stop Mystique, saving all mutants and humans killed by the Sentinels.
In the revised timeline, genetic manipulation, torture methods, and near-death experiences were found to be able to cause an artificial mutation. The genetic manipulation started with a serum used to awaken the X-gene inside a normal human, while the human was then subjected to extreme stress, caused by torture and near death experiences, with some human subjects being put on the brink of death to cause a mutation. However, as not all humans have dormant mutant genes, the torture could end up killing the subjects instead of mutating them. These were used to create super-humans and super-soldiers, conditioned to become strong and obedient. Their were fitted with a device called a Control Collar, which made them obedient to whoever the subjects were sold to. The process usually caused a lose of morality, ethics, compassion, and remorse, leaving most subjects indifferent, cruel, and sometimes, sadistic people with a sense of humor. Notable subjects of this are Angel Dust and Ajax, while Deadpool, another human given artificial mutations, retained his sense of humor while losing much of his humanity and sanity, becoming a humorous, but ruthless fighter and a brutal killer.
- Sebastian Shaw: "We are the children of the atom; radiation gave birth to us. What will kill the humans will only make us stronger."
- Jean Grey: "Ladies and Gentlemen, we are now seeing the beginnings of another stage of human evolution. These mutations manifest at puberty and are often triggered by periods of emotional stress."
- Jean Grey and Professor X: "Mutation: it is the key to our evolution. It is how we have evolved from a single-celled organism into the dominant species on the planet. This process is slow, normally taking thousands and thousands of years. But every few hundred millennia, evolution leaps forward."
- Mystique: "Mutant and Proud"
- Magneto: "Tomorrow, mankind will know that mutants exist. They will fear us, and that fear will turn to hatred."
- Storm: "Neanderthals, we once believed that they were wiped out by years of conflict with a much more advanced branch of humanity called Cro-Magnon, but recent research in to our own DNA suggests that these two species may have inter-bred, evolving into modern humans (asks class) into what? (Class: Us) Us."
- Deadpool: "Chimichangas"