"The Inhumans" created by Stan Lee and illustrator/co-plotter Jack Kirby, debuted in Marvel Comics' "Fantastic Four" #45 (1965). Their home, the city of 'Attilan' is the home of advanced beings, when the humans were still in the caveman era.
"The Inhumans" origins were established millions of years ago, at the beginning of the alien 'Kree'-'Skrull' war, when the Kree set up a station on the planet Uranus, concluding that sentient life on Earth had genetic potential, invested in it by the alien 'Celestials'.
The Kree then began to experiment on primitive homo sapiens by splicing 'Eternals' DNA into 'Cro-Magnons'. Their goal was to investigate ways of circumventing their own evolutionary stagnation, while creating a powerful mutant strain of soldiers for protection against the Skrulls.