Starbound's life-forms make zero sense. The planets you visit are not only Earthlike, but have Earth plants and animals on them. You can fly hundreds of light years in any direction and to squirrels and bunnies playing in grassy fields dotted with flowers and pine trees. All of the sapient races aside from humans are talking animal foreigners: we have Japanese axolotl people, tribal plant people, Aztec bird people, Soviet monkey people, and cowboy sun people. The odds of these species and cultures all independently evolving this way are so slim that the term "astronomical" is much too large to apply. So in the spirit of epileptic trees, I present a fan theory: all of these life-forms originated on Earth. In this theory, the evolution of life is a very rare event. This isn't to say that life only evolved on Earth, but it certainly wasn't so common that you would find life-bearing planets in every system. The Cultivator was one of the earlier forms and reached some sort of ascension point. He didn't particularly care for the overall emptiness of the universe, or for the fragility of planetary biospheres, so once a planet developed life sufficiently to his taste, he took samples from that planet and populated them across other planets in the region. This is why he's called the Cultivator: because he took life from seed worlds and cultivated it more broadly across the universe. This both made the universe a more flowery place and protected each biosphere from extinction if something happened to the home planet. The effect of this would be that each galaxy would have distinct bio-regions dominated by life-forms derived from the local seed planet. Starbound takes place inside Earth's bio-region, but there are other bio-regions out there beyond known space. Obviously not all planets in Starbound perfectly match Earth. Garden planets with earth plants and bunnies also have alien life forms like poptops and whatever those orange bouncy things are, and there are also "alien" planets which are visually very different. All of this life is still derived from Earth, however--it's just evolved in different directions to suit the unique environment of that planet.