Humans are the only naturally occurring race in the universe. Their adaptability allows them to thrive on various planets and galaxies, leading to diverse forms and cultures called Nativities. For ease of translation, humans from different planets are called 'aliens' to each other, or the term 'Native' is also commonly used to refer to humans from different planets.
Nativities can have scaly skin, tough skin, increased life span, capacity to breath ammonia air, special traits and powers, etc.
It is not limited how different one Nativity can be from another, but they all have the basis in Humanity.