Why did Zeus eradicate the corrupt human race with cataclysm and how was humanity re-created?
Titan Prometheus offered the humans many gifts. He gave them the gift of fire, which stole from the gods and was severely punished by the gods for daring to share something so priceless with the human species.
Zeus tied him up in the Caucasus, and every day a vulture ate his liver. Every night it grew since he was immortal, and the next morning the vulture ate it again. So the torments were endless.
The second gift of Prometheus to the humans was his son Deucalion, who was to re-create the human race.
The Flood of Deucalion
People could not properly handle the wonderful gift of Prometheus. They misused the fire and were corrupted to such an extent that they provoked the father of the gods and men. Zeus was outraged at the injustice, violence and immorality that reigned on earth. He decided to punish humanity as a whole and wipe it out with a flood that would drown them all. The only one who was informed of the impending catastrophe was the righteous Deucalion, who was king in Thessaly. At his side was his wife Pyrra, the daughter of Titan Epimetheus, brother of Prometheus.
Her mother was Pandora, the woman who opened the box that hid the evils of mankind. When Deucalion and Pyrra learned of the flood, they built a ship and gathered all the necessary supplies for their survival. It rained for nine days and nine nights. The earth was flooded, people vanished and only the ship of Deucalion and Pyrra survived.
On the tenth day, the rain stopped and the ship ran aground on Mount Parnassos. The couple disembarked and hurried to make a sacrifice in honor of Zeus. The Father of the Gods, delighted with their piety, decided to fulfill their first wish. Without a second thought, they called for the rebirth of the human race. Then Zeus told them an oracle.
If they understood him, they could re-create humanity. He told them that they would have to throw their mother's bones behind their backs. Deucalion and Pyrra realized that the bones were in fact the stones that formed the "backbone" of Mother Earth. So they started walking and throwing stones behind them. For every stone thrown by Deucalion a man was born and for every stone of Pyrra a woman was born.
With the first stone Hellin was born, the "father" of the Hellenic-Greek race. Hellin had three sons, Doros, Aeolus and Xuthos. Aeolus reigned in Thessaly and gave his name to the Aeolians. Doros ruled in Attica and was the ancestor of the Dorians. Xuthos settled in the Peloponnese and had two sons, Ionas and Achaios, who in turn ruled in their respective tribes, the Ionians and the Achaians. The myth of Deucalion is the foundation upon which the rich Greek mythology was built. In many cases, the line between myth and reality was very thin. The ancient Greeks used mythology to explain natural phenomena, but also to keep tradition and history alive.