I'm preparing for a debate (just between friends) on evolution (I'm in support), and one of the points I plan to bring up is the Chromosome 2 evidence. I'm now trying to predict their potential rebuttals. The common statement I've seen is that since the apes have 48 chromosomes and humans have 46, then there are two possibilities: either we "lost" a chromosome, which would be fatal, or there was fusion. This, I believe, was an actual prediction prior to the answer of Chromosome 2 being identified. But couldn't there have been a third possibility - that the apes gained a pair of chromosomes, perhaps thru splitting of some kind? This seems reasonable to me due to the other claim that we didn't evolve from apes but that we share a common ancestor, and so the ape lineage could have acquired the extra chromosome after the split. (Note I'm a total biology noob, so if this doesn't even make sense, then please tell me.) I understand that this isn't the way it turned out, that Chr 2 looks exactly as we would expect from fusion, but prior to this discovery, couldn't the apes gaining a chromosome have been a possible reason? TIA.
I guess part of the question is...what exactly are you bring up Chromosome 2 as evidence of, exactly? It's evidence of that chromosomal rearrangements are possible, but that isn't terribly helpful to you, so I'm not sure why you are bringing it up.
I think the fusion is a rebuttal to a claim that the disparate # of chromosome is a problem for the claims of common ancestry between humans and other apes, but if they don't mention it, I'm not sure why you would need to use that particular fact.
Have you consulted talkorigin's 29 evidences of macroevolution? Lots of good stuff there.