Rebirth Explained

I have read Osho saying somewhere that once we reach to the human level there is no chance of going backward. Reason is that birth is only because of unfulfilled desire/experience. In the case of human desire to experience other forms of life is no more there. One more important thing is that we the life as such don't take births because all of us part of the same life. Basically thoughts representing unfulfilled desires take birth in order to get themselves fulfilled. Concept is that the thoughts are subtle form of life. All the lives want to continue itself (jiveshna). To manifest and continue energy is required. To produce energy the proper instrument is required. But the trouble with the thoughts is that they do not have proper instrument to produce the required energy for their continuation. Hence they become parasite and thrive on our energy. That is why average brain although being only 2% of total body weight consumes 20% of total energy produced by the body (medical facts). What happens in the end is that there remain many unfulfilled desires. All these desires try to continue its life but the instrument supplying energy is no more working. Hence they start searching for a suitable body in order to complete their life cycle. Some of them or all of them (who knows) get body in the womb. When the child comes out from womb he does not remember the thought because of nature's mechanism of placing those thoughts in unconscious part of the brain. Sometimes due to fluke of the nature the thought slips into conscious part and one starts remembering his earlier birth because of the fact that that thought was related to other thoughts of those time/that of previous instrument.

The above should be taken just as concept to understand the phenomenon of rebirth. It is like in school we used to take x=5 at the start of solving a mathematical problem. In the end x is no more there. The above concept is like X