One theory of how life arose on earth is that of panspermia, wherein single celled organisms like bacteria hitch-hike on a comet or meteor which then impacts the Earth.  If that was the case, then we are all alien descendants.

Such a meteorite has possibly been found in Sri Lanka!  http://www.technologyreview.co.....-fireball-fragments/

The rock contains fossilized remains of carbon marine life, which scientists have concluded could not have been the result of contamination upon entering our atmosphere.  Of course such a controversial find will have to be reviewed, but if the discovery stands up to scrutiny, these fossils are extra-terrestrial, and prove life exists elsewhere in the universe.