The theory that all life on earth evolved from unicellular organisms is untestable.
Nope. The opposite. Your statement is simply untrue. The oldest fossils are those of unicellular, prokaryotic organisms. Tested. Done. Geology. In SA, WA and Greenland.
Actually, I concede that Clown fish present convincing evidence of evolution. There is a well-defined line of descent from Clown bacteria...
Actually, some unicellular organisms do have to have sex with themselves to be able to reproduce. Those organisms don't have to wear clown uniforms or paint their faces red or even blush about it. So, what's your point?