No matter - this also would be a conclusion that has nothing to do with the premise, to wit: X is similar to Y in Z, therefore X and Y evolved from K. Huh? that doesn't follow either, does it?
You are half-educated in logic. When I say "gee, doesn't this here thing look pretty similar to that there thing, I am drawing on the powers of analogy to suggest a possible relationship. This is called analogical reasoning, and is not subject to the law of the excluded middle. Look it up. Scientific theorizing leans heavily on this process. Since I am not arguing from absolutely established facts, such as to be grouped in sets by their attributes with formal assurity, the law of the excluded middle is not merely irrelevant, it is wrong. It is excluding possible relationships that it is not correct to formally exclude, since the current state of our knowledge is that they only exist conditionally in theory-sets, as a cloud of probability.
The discrete laws of traditional logic apply to what mathematicians call well-defined domains of discourse. The theoretical meaning of scientific facts is not any such domain. What theory-set a fact may belong to is forever up for grabs. All we can do is increase our confidance in a theory, we cannot prove it correct. Proof is beyond our capability, so the laws of formal proof are moot except as technical analytical tools for making oscilloscopes and such work.