The existence of extra-terrestrial but separately evolving humans would suppose at least carbon chemistry (which we do know is amazingly diverse), that's a start; then polypeptides, fair enough, amino acids exist in space; but then the DNA/RNA with its encoding, is that unique? Is even the genetic code unique or arbitrary; then the particular "implementation" of the protein based form of life. I'd say that rather considerable improbabilities mount up.

I could go on. For goodness sake, I and others have been battered to the point of abuse for even entertaining the idea that extra-terrestrial life is not incomparably different, now we are told that we cannot rule out convergent evolution on an "astronomically" improbable scale.

I do not think it unreasonable to point out that, although there may or may not be roughly analogous biospheres, we already have enough information to suggest that it is extremely improbable that they would be fully cognate with our our own chemistry, let alone our actual phyla.

And if there were, I would say that we might make some quite astonishing deductions from that possibility.