The first man on earth is Lord Manu. Their offspring are human beings. Surya's son Vishwan, Vishwan's son Ikshvaku and Ikshvaku's majestic son Manu. He saved the god who was in the form of a fish in a fish during the flood on earth and gradually put it in a puddle, well, lake, lake, river and sea and saved his life. So Manchula saved Manu Bhagwan at the time of the cataclysm of the universe. Then the earth re-emerged. The period between one such Manu and another Manu is called Manvatar. Manu Bhagwan has written a book called Manu Smriti to guide the people on earth on how to live. It is still famous today.