During the creation of the sun of water, humans began to defy the gods. Except for two humans named Tata and Nena.
The water god, Tlaloc, became very angry at the humans and decided to have a flood occur to rid the world of them. However, Tlaloc had warned Nena and Tata of the flood and prepared them. He told them to get a canoe and two ears of corn, one for each of them to eat. They were not allowed anything else to eat.
The flood had occurred and killed all of the evil humans.
Nena and Tata were the only two humans that had survived and they were so excited when they landed somewhere safe. They were able to catch fish. Forgetting Tlaloc's rules they both happily ate the fish that they caught.
When Tlaloc had found out of them eating something other than the two corn they were allowed he turned them both into dogs.
The gods were so frustrated at the last two humans that they believed were good that they decided to destroy this world. This resulted in the creation of the fifth sun, the earthquake sun.