- "Mutation: it is the key to our evolution. It has enabled us to evolve from a single-celled organism into the dominant species on the planet. This process is slow, and normally taking thousands and thousands of years. But every few hundred millennia, evolution leaps forward."
- ―Jean Grey
Mutants, also known as Homo-superiors, are individuals who possess a genetic trait called an "X-Gene" that allows them to naturally develop superhuman powers and abilities and sometimes affecting their appearence. In X2, it is explained by Pyro that the males are the ones that carry the mutant gene and pass it on. Mutants are members of an evolutionary progeny of Homo sapiens and are considered by many as the next stage in human evolution.