If there are sentient beings on other worlds, and they are NOT the descendants of human beings from Earth, it would invalidate a key teaching in the Talmud [Sanhedrin 37a, 38a]:
-Why did God start humanity by creating only ONE man?
-So that unbelievers would not be able to say: There are many authorities in Heaven, and each created a different person.
-So that no one should be able to tell his neighbor, “My ancestors were better than your ancestors”.
-So the wicked could not say: “We are children of the wicked, so we cannot change our ways.”
-So the feeling of fraternity among people will limit crime.
-So people would know that God is One: Even though God created people in His image, every person can still be different from every other person: Unity in diversity.
-So that people would know that he who destroys one life is as if he had destroyed an entire world, and he who saves one life is as if he had saved an entire world.