Prior to the creation of humans, the gods established corn as a symbol of the cyclical nature of life, but in human form, it truly comes to represent life itself. Unlike the gods, who used corn only as a symbol, for humans, corn is very literally what makes them human—Xmucane shaped humans' bodies out of corn, which ties human life to the gods. In a practical sense as well, corn literally keeps the Mayan people alive as one of their most important staple crops. This further reinforces the link between corn and life, as life would be nearly impossible without corn.
Corn Quotes in Popol Vuh
And this was when their grandmother burned something, she burned copal before the ears of green corn as a memorial to them. There was happiness in their grandmother's heart the second time the corn plants sprouted. Then the ears were deified by their grandmother, and she gave them names...
It was staples alone that made up their flesh.