1) the life form is just a radically evolved version of a previous life form that has changed over millions, even billions of years, to the point where it looks very different. In other words, it's still related to Life 1.0 but been modified to a high degree
2) the life form evolved on earth but its origins are not the same as any other organism. We call this possibility Life 2.0 suggesting an entirely separate branch of life on the same planet.
3) the life form evolved on earth but responded to external factors. For example, if we found an organism using right-hand amino acids there is the possibility that this organism evolved in a region of the earth peppered with right-handed amino acids delivered by meteorites.
Or it could be all of the above! So unless the life form is *very* different, it would be difficult to be certain.
-
Michael say: If they were from outside earth. You would'nt be able to find them, but a new species from earth are only content in doing what their doing & not excited by you as an outside species would be. Mike
-
Nyx say: Species are related. They are at the end of Linnaean classification system. DNA, and taxonomy proves that.
For something alien, you would need to look at the beginning of the classification system, such as kingdom, or phylum. A course in fundamental biology will clear that up for you.
https://www.sciencelearn.org.nz/resource...
-
Gray Bold say: The kinds of living organisms currently known on Earth all use carbon compounds for basic structural and metabolic functions, water as a solvent, and DNA or RNA to define and control their form.
-
Bob B say: There are a few clear reasons why we know this:
1- They tend to be very similar to other species on Earth. For instance, pretty much all vertebrates- all mammals, reptiles, birds, etc, are all actually very similar; if you cut them up, they have largely the same organs and the same basic pattern to their skeleton; different parts are different sizes but they are all variations on the same general theme. Same for arthropods, molluscs, etc. It would be very unlikely for aliens from another planet to have almost the exact same basic structure.