The concept of reincarnation is a belief found in several religions and philosophical traditions, such as Hinduism, Buddhism, Jainism, and certain New Age or spiritual belief systems. It posits that after death, the soul or consciousness of an individual is reborn into a new body, either human or non-human, in a continuous cycle until certain spiritual goals or enlightenment are achieved.
Regarding the question of what happens when there were no humans on the planet or when there will be no humans, the belief in reincarnation suggests that souls or consciousness can be reborn not only into human bodies but also into non-human bodies or life forms. So, during times when there were no humans or when there may be no humans in the future, the cycle of reincarnation would continue, and souls could be reborn in other living beings or forms of life present on the planet or elsewhere in the universe.
The idea of reincarnation encompasses a broader view of life and consciousness beyond just human existence. In this belief system, the progression of souls through various life forms is not solely dependent on the presence or absence of humans on the planet. It is a process that is not limited by time or human population, but rather a continuous cycle of birth, death, and rebirth, involving all living beings in the cosmic existence.