What came to earth first?
You are all answering the question in errored assumption. The question is “What came to earth first” not “what evolved first” The question pertains to “space and astronomy” so therefore the only logical answer is…. The space chicken came to earth first on an Omega-Class Royal Cruiser and laid an egg that hatched the first lifeform. All hail the Mighty Space Chicken, the One and the Only, the Holy Plucker, the Great Layer of Egg-life.
