Matter and energy can neither be created or destroyed. They can only change forms. Rather, matter is dense energy. When a body exists ( it is not one body from birth to death, cells die and new cells are formed round the clock ) something has caused all these atoms and molecules to come together and stay together for a period of time. At death, the body disintegrates into the fundamental elements again. Will the underlying cause, which made the body to come together make it to happen again in the same combination ? meaning a rebirth.