Humans are mostly extinct. Human civilization was wiped out, and Earth is now an "uninhabitabable mudball". The only known humans are Iris, Tye, Z and a handful of other unnamed research subjects.
The details of the catastrophe which wiped out humanity are as of yet unrevealed.
Humans choose a name for themselves at 10 years old.
When humans on the space station are deemed "ready," probably by means of finding three things they take an interest in, and then further studying those things (which most kids on level two already have).
Level 1 subjects
Level 2 subjects
Level 3 subjects