Board Thread:Spoilers/@comment-28118206-20160403030006/@comment-189.47.54.51-20180908192736

Natblida is a recessive genetic condition. Many grounders have the Natblida gene, but only when someone born with two Natblida genes (both parents carries the gene) this person will be a Natblida.

Even if all Natblida died, they continued to be born.