The Maya built their sacred calendar out of the human gestation period: they looked into their bodies rather than up at the sky.

Archaeologist and director of the Maya Exploration Center

I mean, if that’s right, that means the Maya and the people of Mesoamerica will all share it together, when they thought about, “We need a count of time for us,” they didn’t look up into the heavens, they looked into their bodies. “What’s the first cycle that we actually go through as humans?” and they picked this nine-month thing. It really is our cycle, and no other culture on the planet looked inside themselves to create their calendar like that.