We have 2 or more sources, the info left on the walls of the Pyramids and those that possess the ability to remember or even control what goes on in their dreams.
Why we choose a mortal body? Some have written that some return to aid those in need, others have written we are all climbing the ladder and must learn what we must while on earth. Many speculate why we have blood so similar to a fish and the questions are endless. I believe while your asleep there are no questions, we are only in the dark while awake. I ask my self many times why God allows a few to spray chemicals upon our heads every day, it is not for us to know, but to experience.
An example of life and death. When I was a child I asked my Dad what it is like to die? He simply said to die is like cutting your finger nails, no pain. Tonight Dad was set free, he had been suffering for many years the results of smoking for a lifetime and his oxygen was very little and he was not eating or drinking due to a new drug that was started 5 days ago. I simply applied Frankensense and Myrrh oils to his head and told him it was OK to go home, in 30 minutes he left with no struggle and a totally warm body down to his toes, not the frozen body you have in a hospital on drugs.
We are told we can go to Hell, the old books state to live on earth is to be bound to a body and that is Hell, to be set free of the body was known as returning to Heaven, I guess we all know the truth someday. I have talked to many people who seen their parents at the foot of their bed the moment of death even thousands of miles away, I believe true freedom only comes when free of the body. Authors who seem to know, say when dead, we have a body that feels just like this body, that we are just in a differant vibrational state. Why we live for ever and end up being put into a new baby to live life on earth most likley is an honor, we must like the feel of this body OR maybe we were bad and this is a sentance non like jail, I have not a clue. Many things will always be a mystery, it makes life worth living.
I also have read that our little new borns and small children are the angles that protect us older people who have lost our connections, I tend to believe this. The little ones are guided very strongly while us older folks slide through life not knowing what were doing 1/2 the time.