Life els where in the universe.. they too are aliens like u are. Universe?

It depends where they come from I think, we developed this way because of gravity and that we crawled out of the ooze like fish with gills and we learned to breathe air in our atmosphere. So what if there IS life on say Mars but it is still like a bacteria or an extremophile that lives in the harshest of conditions. I don't think they would have 2 arms and 2 legs like us, that would be a really big coincidence to me and unbelievable.