And if special creation is the “working hypothesis”, fusion is STILL the only logical conclusion.
I forces a deeper understanding of the issue which hopefully we get to. If the evidence is very strong as Kurt Wise says then it strengthens the case for primate common ancestry.
How does assuming YEC force a deeper understanding?
Wouldn’t that violate YEC? Are you saying we must destroy YEC in order to save it?
My experience is that they usually start of denying the fusion ever happened, and eventually retreat to “but even if it did then it just happened in the human lineage sometime after Adam and Eve”. I don’t get the impression that they’re particularly interested in the fusion itself, instead they’re just trying to rebut it as evidence for evolution, one way or another.
Why would you want to make a conclusion based on a already long falsified YEC model?
Common descent isn’t a working hypothesis Bill. Common descent is a well established scientific fact. Your silly game of trying to establish some false equivalency between YEC claims and scientific facts is just, well, silly.
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Why? The fusion is compatible both with common descent and special creation of human, for the fusion event could have occurred after Adam and Eve.
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Evograd sure called that one. 
Of course Creationists are still using a page from YEC Tactics 101. Demand every piece of evidence be considered all by itself, in a vacuum, with no regard for how it fits in with all the rest of the physical evidence.
Because evolution predicts it, creationism is merely compatible with it. I wrote about this, wow, nearly 4 years ago now. Time flies.
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Fusion isn’t evidence of common descent, but removes a supposed obstacle to common descent, i.e. the difference in chromosome number.
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Absolutely
I disagree. See my blog post above for the full explanation. A fulfilled prediction explicitly made by one model and not by another constitutes evidence in favour of that model.
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I don’t like that calculation. You give P(D|H) as 1, but that makes no sense to me. You could apply that method to sequence data as well and end up with likelihood scores of 1 for every tree. In that context it’s clearly false, and I don’t see a difference between sequence evolution and chromosomal fusion. The probability of observing what we observe is never 1, as it’s understood in phylogenetic analysis.
It doesn’t have to be 1, the point is simply that it is very high.
As I said in the subsequent paragraphs:
The key point here is that because creationism doesn’t necessitate the fusion, and is only compatible with it, the probability of observing the fusion IF creationism was true is always going to be less than 1, meaning that P(D) on the denominator of the equation will always be lower than 1 (but still higher than 0.5), ensuring that the posterior probability of common descent being true will always be higher than 50%. This would also work with any other value of P(D|H) that is higher than P(D|H’), where H’ is the creationism hypothesis, so the numbers are quite flexible.
You can verify this for yourself using this calculator. Hypothesis I is common descent, hypothesis II is creationism. Play around with the numbers in the left-hand fields until you’ve convinced yourself that as long as the prior probabilities of the hypotheses are equal (50-50), the hypothesis with the highest likelihood will be favoured. As I’ve explained, the true likelihoods are essentially 100% and 50% for common descent and creationism respectively, but all that’s really required for common descent to be favoured by the fusion is for common descent to “need” the fusion more. At the moment the calculator is set with the numbers we used in the calculation above.
What is the YEC explanation for why extant Equus species have such widely varying chromosome numbers? How many chromosomes did the Ark horse “kind” have?
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I would disagree. I would say that the probability is very low. Chromosomal fusions are very rarely fixed, and the probability of such a thing happening on the human lineage is tiny. Further, it’s the same probability regardless of whether that lineage is attached to a tree or separately created. The actual reason that, in this case, the tree is more likely than separate creation is that the tree gives a unitary explanation to the original states (48 chromosomes) being the same.
Note that common descent doesn’t necessitate the fusion any more than it necessitates a change from C to T at some site. The probability of the observed data, given a tree, is always very low. In this case it’s identical to the probability of the data given an isolated lineage.
The difference in chromosome count is an obstacle, yes. However, that obstacle lends itself to an extraordinarily specific prediction. That extraordinarily specific prediction is the one which was tested and found to be true.
The specific prediction is that the human ancestor had 48 chromosomes. And I don’t think Bayes’s Theorem can be used in the way @evograd has used it. Determining the probability of the data requires some distribution of probabilities, and the obervation of a particular state is not a distribution.
No, I don’t think it is. It’s an obstacle unless there is such a thing as chromosomal fusion. Fortunately, there is.
Yes, I agree that evolution predicts it, the same way that if it rains, you can predict that the grass will be wet. But the fact that the grass is wet doesn’t allow you to conclude that it has rained.
It does though, because the observation that humans possessed 46 chromosomes while our alleged closest living cousins the chimpanzees, as well as all the other great apes, possess 48 was made, which led to the fusion hypothesis.
At that point, if common ancestry of humans and the great apes was true, there had to have been an event that accounted for our different number of chromosomes. By far the mostly likely option was a chromosomal fusion, so given the data available, the theory of common ancestry all but demanded that the fusion occurred. It is in this context that the evidence for the fusion is considered as a fulfilled prediction.
Sure. But your Bayesian approach does not, in my view, handle that prediction. You can’t call the probability of observed data 1.