Thrive: An open-source evolution game inspired by Spore
Thrive: An open-source evolution game inspired by Spore

revolutionarygamesstudio.com
Thrive | Revolutionary Games Studio

https://github.com/Revolutionary-Games/Thrive
This entertaining game aims to be a scientifically accurate evolution game, starting off as a single-celled organism and growing into more complex organelles, competing against other organisms in the environment.
https://store.steampowered.com/app/1779200/Thrive/
It is still in active development and later stages aren't fully fleshed out yet but the early stages can still provide a few hours of fun.