Most of the superhumans in Marvel's Earth owe their powers to the celestials, cosmic entities who visited Earth millions of years ago and experimented on our prehistoric ancestors (a process they also carried out on several other planets). This resulted in the creation of two hidden races, the godlike Eternals and the genetically unstable Deviants, in addition to giving some humans an "x-factor" in their genes, which sometimes activates naturally, resulting in sometimes superpowered, sometimes disfigured individuals called mutants. Others require other factors (such as radiation) for their powers to come forth. Depending on the genetic profile, individuals who are exposed to different chemicals or radiation will often suffer death or injury, while in others it will cause superhuman abilities to manifest. With the exception of psionic abilities, these powers are usually random; rarely do two people have exactly the same set of powers. It is not clear why the Celestials did this, although it is known that they continue to observe humanity's evolution. A Marvel series titled Earth X explored one possible reason for this: that superhumans are meant to protect a Celestial embryo that grows inside the Earth against any planetary threats and have done so for eons. An X-Men villain known as Vargas claims to be a new direction in human evolution, as he is born with superpowers even though his genetic profile said he was an ordinary human being. The majority of the public is unaware of what may cause superhuman powers.