Bierhorst's translation of the Legend of the Suns names Quetzalcoatl as ruler of the Second Sun, called 4-Wind, following his defeat of Tezcatlipoca at the close of the First Sun. Humanity in this age lived under Quetzalcoatl's rule until a catastrophic wind, a hurricane of a violence the text treats as world ending rather than merely destructive, swept across the earth and scattered its people.
The survivors of that wind were transformed into monkeys, a detail the Legend of the Suns ties directly to the day sign Wind that names the age, and which Miguel Leon-Portilla reads as characteristic of the Five Suns narrative's broader logic, in which the manner of each age's ending leaves a visible trace in the natural world that followed it, whether animal, as here, or geographic, as in the floods and fires that end the ages on either side of this one. Monkeys held their own place in the Aztec calendar independent of the Five Suns story, as Ozomatli, one of the twenty named day signs of the tonalpohualli ritual calendar, associated with playfulness and artisanship; the Legend of the Suns' choice to transform the Second Sun's drowned or scattered humanity into monkeys draws on an animal already carrying established symbolic weight elsewhere in Aztec religious thought, rather than inventing new significance for the species.