The doctrine that human souls pass from one body to another at the time of death

One word substitute is Transmigration.

Metamorphosis: biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.
Transition: the process or a period of changing from one state or condition to another.
Transmigration: the movement of a soul into another body after death.
Extrapolation: the action of estimating or concluding something by assuming that existing trends will continue or a current method will remain applicable.