abductees are chosen out genetic lineage. Because humanity itself is a composite of many "alien" genetic types. The ET's abduct often
1) people of their own soul nature, aka starseeds
2) people of the genetic descendents of the original races (the greys for example)
3) both of the above.
This is why GENERATIONS are abducted through out their lives, and so is their families. They are tracked from generation to generation. Its actually quite complicated from what I know.