A while ago someone mentioned that we all all start as a Human and later on get a choice to stay Human or become Exo/Awoken. So I think it will be tied to a storyline or path that you follow. For example an Awoken storyline (just an example, don't hate): After days of ripping the mindless Hive apart you reach the Queen. You're surprised to find her alone. She turns around and approaches you until you can smell her rotting flesh. She speaks, but the words appear in your head instead. "You're the first, Guardian." she says. "Everyone must die eventually" you say. "I can not die, it happened a long time ago, fragile mind. If you shoot me, your bullets will be wasted. If you strike me down, you will see that it does not affect me. Even your Traveler won't do you good in here." You quickly grab your best gun and shoot her straight between the eyes. You hear the bullet hit the wall behind her. She lifts her figher and touches the gun. It immediately freezes and crumbles before your feet. "Don't you see, Guardian, you have no chance. No victory. No future. No life. The only path you have left is to join me." The same finger that touched your gun penetrates your armor like it is nothing, straight into your chest. You feel the cold entering your body, the life flowing out of you. You know that you are dying. You're overcomee with peace as there is nothing left that you can do. Suddenly the rest of your fireteam reaches the same chamber and start throwing everyting that they have at the Queen. Then with a flash she is gone, not one trace left. Vanished. Your team brings your body back to the Last City as you're balancing between life and death. The physicians know that only the Traveler can help you and ask the Council for permisison to put you in the heart of it, where the power is at it's strongest. There you lie for weeks when you emerge as something else. The Traveler replaced the cold in you, left by the Queen, with it's own power. You're changed inside but also from the outside. You're Awoken. Exo storyline: You are victorious. The battle in the Dead Forest between you and the Cabal is yours. You've taken the smaller Cabals, responsible for the maintenance, as prisoners as they are too weak to fight. The other fireteams start to collect the wounded to bring them to your ship as it is equi[ped as a temporary field hospital. You decide to go to your quarters to fresh up when you walk past the wounded. There is no glory in there. Only suffering. One boy strikes your eye. He's can't be older than 15/16. The field medics are trying to get him back, to kickstart his heart, but it's too late. You see that one small group of your prisoners is also looking at the boy and discussing things with each other. You feel the anger rising and grab one of them. "You like what you see?!" you say. The little Cabal looks nervously to his friends. "Tell!" they say. "Tell me what, Cabal!". "Wel.. uhm.. lord Guardian.." he says. "We can safe the small Guardian.." You can see the fear in his eyes as he knows for sure that you will shoot him. You look at the boy, lifeless. "Do it." you say and you put the Cabal down. They immediately start working on some device that they picked up outside. All are eyes are looking at you, whispers can be heard. You hope that you've made the right decision. They come back with a small egg formed thing and give it to the field medics. "Put it in!" they say. You nod and they start the surgery. The small Cabal advise them on the way as the field medics remove the heart and plant the device in. The body of the boy starts to shock and glow. After a while it stops and you can hear him breathing again. One of the Cabal approaches you. "This will keep him stable for now, but we need to fabricate more for him to keep him alive. We can do this in a matter of days as our equipment is still in our base. We only ask our freedom in return." A few days later you set the Cabal free with some supplies to make it back home. The boy is unrecognisabe, full of mechanicle parts. He's clearly awake but says nothing. Then he looks at you and says with a strange voice "Thank you". "What was there on the other side?" you ask. You trie to look him in the eyes but they are also gone, replaced with strange lighting. ".....Nothing.. nothing but darkness." So to answer your question: I think they're cyborgs :)