Grounders, often called Savages by clones, go by many names:
Natives, Urbanites, Denizens, Bunker-Dwellers, Mountain People, etc.
It doesn’t matter the name you give them, for they are as versatile as the world they live in. These people are descendants of survivors of the bombs. Living within bunkers, bomb-shelters, and government facilities until radiation had lowered to a manageable level. These people are highly motivated by survival and are their primary objective in life. Though they are human and come just as unique and varied as they can. They are NOT clones and are not a natural part of the Eden Project. They have become the variable in the equation.
How did Grounders survive this long?
The earth has only been humanly inhabitable for the last 50 years. Any grounders would have had to come from some safe, protected area. Where that is, how your family/group/town got there is more or less up to you. If you want to combine stories with another group, you are free to.
Given the nature of the wastes, some people may have suffered long-standing family mutations or new ones that have begun to appear once they came surface side.
What is a Mutation?
Do I have to take a mutation? Can I have more than one?