Here is a new open-access paper, published in Frontiers in Microbiology, that is instructive: “Eukaryogenesis: The Rise of an Emergent Superorganism.” Author Philip J. L. Bell begins:
Although it is widely taught that all modern life descended via modification from a last universal common ancestor (LUCA), this dominant paradigm is yet to provide a generally accepted explanation for the chasm in design between prokaryotic and eukaryotic cells. Counter to this dominant paradigm, the viral eukaryogenesis (VE) hypothesis proposes that the eukaryotes originated as an emergent superorganism and thus did not evolve from LUCA via descent with incremental modification. [Emphasis added.]
The “chasm in design”? For a theory (i.e., the universal Tree of Life, rooted in LUCA — universal common descent, or UCD) whose empirical strength is so great that it cannot be doubted, UCD certainly is doubted a lot.
Doubted by biologists, in fact, with no known interest in intelligent design.