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.
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1$\begingroup$ does this help? biology.stackexchange.com/questions/5558/chromosome-2-fusion What else might you need? $\endgroup$– shigetaCommented Jan 20, 2014 at 11:02
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$\begingroup$ BTW splitting happens too. $\endgroup$– shigetaCommented Jan 20, 2014 at 17:11
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$\begingroup$ shigeta, i saw that article and read it before I posted this question. That page doesn't seem to answer my question directly - specifically, WAS IT PREDICTED or was it simply taken as evidence once it was discovered? So ideally, someone could provide a reference to a paper or article that was published that says "we predict that...two chromosomes will appear fused", and which was subsequently confirmed by a later paper or article. I've heard it was about 30 years, but I have no valid source. $\endgroup$– Michael BrayCommented Jan 21, 2014 at 2:03
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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.
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$\begingroup$ It is useful, IF it was predicted. This is one of the main differentiators between valuable theories and useless theories, and hence this is why I'm asking the question. Creation, even if it allows fusion, doesn't predict it. Given that apes have 48 and humans have 46, the "prediction" from creation would be "that's just the way god made it" and say nothing about fusion. But evolution's prediction would be that we would see fusion (or other effects) and that's why it is useful. $\endgroup$ Commented Jan 22, 2014 at 2:27
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$\begingroup$ Things don't have to be useful to happen in evolution. They have to (at the time they are happening) be no disadvantage for the organism. And no, you can not predict, what is going to happen in evolution as this doesn't follow a certain path. You can think about things that can happen (as is has with the chromosomal difference between human and ape) but it doesn't have to happen. It is a proof for a common ancestor to compare genome sequences and there where the differences are. $\endgroup$– Chris ♦Commented Mar 22, 2014 at 20:09