Assuming 'X' is humans, 'Y' is chimpanzees, 'Z' is gene sequences, and 'Q' is a common ancestor, then I am curious as to your evidence that the conclusion of 'X' and 'Y' must come from 'Z' does not follow the predicted premise.
It doesn't follow because the conclusion has absolutely no relationship to the premise. Q isn't even involved in the premise. There not only is no logical reason, but no hint whatsoever in the premise that X and Y evolved from Q. Q just appears out of nowhere. Can you see that?
Here is another fallacy I didnt' mention: The attributes of a part cannot be applied to the whole.
Notice the first part of the logical premise by evolutionistis: X is SIMILAR to Y in Z. Similar is not the same as IDENTICAL, so the fallacy of equovication also applies. Humans and giraffes have the same number of neck vertabrae - should we assume we share a common ancestor with them?
Here's another important point: The evolutionist is assuming that the existence of similarity in designs or processes is evidence AGAINST design, when in fact this type of evidence is perfectly consistent with a designer.