[@obisemkenobi] 1) you can be Dutch, there are pockets of survivors but only way to get the training necessary to be chosen is to have left years ago. Not to mention health issues with living in an irradiated wasteland.

2) Security has an Investigation branch which aren't necessarily military personnel and while they fall under the security branch they can follow the trail of clues wherever it goes.

3) they were selected, as Genesis Protocol wasn't made public till they had already started crewing the Arks. There'd be a host of medical and psychological tests to make sure they were worth having aboard.