If by "We" you mean Humanity then yes we originated on earth. We descended from a common monkey ancestor from the great apes. Hate to break it to all the conservative Christians, but we evolved from monkeys. We as humans are nothing more than highly evolved apes.
If you mean "we" as in life on earth, then I think there is a strong argument that we may have been delivered here on an asteroid from another planet where life evolved before being blasted off its home planet by a comet impact or other equally destructive event.