Greenlanders are essentially like real life humans. They don't have many stat bonuses and are the baseline for the game's hunger rate.
Scorchlanders are humans with black or blue-black skin and glowing eyes. They have stat bonuses mostly centered around crafting skills.
According to bits and pieces of clues displayed throughout the world of Kenshi, ancient Humans created titanic Skeleton beings alongside smaller, more "worker drone"-esque Skeletons before becoming dissatisfied and disgusted with their creations, committing a mass genocide at Obedience.
- When the game first released, this was the only available species.