Someone said :
yeah but "we" what, as mold? as bacteria?
We can trace our genetic ancestry back to dinosaurs and further back to the basic building blocks of life.
If life came from elsewhere in the universe, it came as something very, very basic.
I reckon we grew ourselves here with only minor influence from the greater universe.
There is nothing close to what we call "life" that can survive, billions of years frozen/incinerated/crushed/sterilized by space. a comet/meteor has no protection from the freezing, radioactive and vacuum of interstellar space, there is just nothing "living" that could make the trip.