Last night PBS aired Two Spirits, the season finale of their Independent Lens series, which detailed the traditional Navajo belief that there we are living in a many-gendered world, one that includes many more sexes that just male and female.

Filmmaker Lydia Nibley seeks to explain the Navajo idea of the nádleehí, which translates in English to "one who constantly transforms." Their culture, along with other Native American heritages, believe there's at least four genders: male, female, male with a feminine essence, and female with a masculine essence. Learn more in the short clip above, and for more information on the film, visit the official PBS website.