As living human beings, we are bound to every other living thing that exists in our world. Put another way, as human organisms, we are meshed into the Web of Life woven by all other living organisms of our Planet Earth. We would not exist without all these microorganisms we depend on to survive, and we would not be living the way we are were it not for all the plants and animals we depend on to make our species thrive. To put that into perspective, project this interdependence through an ever expanding mantle of species and factor in evolutionary time, and a gigantic three dimensional Web of Life emerges.
We like to refer to ourselves as earthlings, but technically all life forms on Planet Earth ARE earthlings. When we venture beyond the bounds of earth, not only do we launch humans but also all those inseparable body microbiomes associated with them, along with all these stray stow-aways on board, microscopic and otherwise. These in addition to earthlings we intentionally take on as cargo such as living specimens we intentionally take to perform experiments, to grow food in future endeavors or even to support and enhance living conditions both in transit and in establishing an extraterrestrial human foothold. The provisions for sustenance are 100% earthling-derived products!
I have to sign off for now, but think about that for a minute, earthling human!
The Garden of Earthen Zen 