[323]

You make a big assumption, that there must be only two kinds of cells, "simple" and "complex", like on earth.

That could well be an accidental fact. Maybe on some planets we have a gradient of cell complexity.

Also, we don't really know what even simpler kinds existed on earth but were lost, since bacteria, the "simple" kind, it's obviously too complex to have been the first ever life form.

[andrewflnr]

That's not even true on earth. Archaea exist, and eukaryotes span a pretty wide range of complexity themselves.