Across media I've seen a lot more of "species with only one gender" (e.g: Mass Effect), "species with no concept of gender" (e.g: Steven Universe). This probab

Across media I've seen a lot more of "species with only one gender" (e.g: Mass Effect), "species with no concept of gender" (e.g: Steven Universe). This probably makes more sense given how often sci-fi is about social commentary, and gender equality is more accepted these days, while gender identity is a bigger issue. In the case of Steven Universe the creator Rebecca Sugar recently gave an interview to NPR (https://the1a.org/audio/#/shows/2018-07-09/the-mind-behind-americas-most-empathetic-cartoon/114886/ https://the1a.org/audio/#/shows/2018-07-09/the-mind-behind-a...) where she revealed she identifies as non-binary and having gems be genderless but female-coded in the show is a good expression for that. The only example of this trope I can think of is the Anime series "Vandread" where somehow humanity ended up being split into a male planet and a female planet, so long removed they no longer recognise each other as the same species. It's basically just an excuse for the male protagonist to come across a ship of women, etc...