Well, that’s quite something. While I thought it was known there was a fusion somewhere, I didn’t realize they knew at that early date which chromosome it involved.
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The relevant quote:
Chromosome No. 2. We suggested previously that a fusion between two acrocentries (referred to as [2p] and [2q]) occurred in man. That two such acrocentrics
homologous to the human 2 exist in the chimpanzee is indisputable. Difficulty
arises in explanation of the exact type of fusion. Our observations on the orangutang (Pongo) and on the gorilla had led us to conclude that the ancestral [2q],
which is apparently unchanged in Pongo, lost its juxtacentromeric dark region
(R bands) in the chimpanzee and the gorilla, but retained it before fusion occurred
with [2p] in man. This is exemplified in Fig. 3. However, Lejeune (1973) suggested
that a terminal fusion occurred in man between the short arms of [2p] and [2q],
thus producing a dicentrie chromosome, and that one of these two eentromeres was
secondarily “lost” during evolution. This view might be acceptable when the
karyotypes of man and chimpanzee are considered, but necessitates another
rearrangement in Pongo. In our view, the question of the exact type of fusion
remains open.
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Hi @Faizal_Ali, @Rumraket, @swamidass, @Witchdoc, @CrisprCAS9 and @evograd,
I have a simple question. Does anyone know when this fusion event occurred?
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One paper I read estimates around 700 kya.
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this isnt entirely true. prof ken miller for instance think its the only possible explanation. im glad to see that we both think he is wrong about that.
see below…
thanks but it seems that my initial notion was correct. as you can see in fig 2 (and fig 3 in the older paper), these two chromosomes overlap each other (which means that the genes are not missing):
thus, that fusion isnt even a prediction but an observable fact, and thus even ID “predict” that.
Accepting common descent would lead to the prediction that the genes are not missing.
You really do not understand this topic at all.
Please explain how ID would predict the existence of residual fragments of telomeres and centromeres in Chromosome 2.
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No, he doesn’t. Quote him saying that. From his presentation I explicitly remember him saying one alternative option was a series of fission events in the other great apes, for example. This is ruled out because it’s unlikely, not because it’s physically impossible.
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There have been several estimates, ranging from ‘recent’ (the 0.7Ma number @swamidass referenced) to ‘early’ (~3.5Ma). The confidence intervals overlap around 3 Ma, so that’s where I’d put my guess.
On the other hand, does identification of something as a fusion require knowing when it happened?
Is Ken Miller here? I didn’t realize he was a member of this board, nor have I seen him active in this thread.
My impression of Miller’s statements is that a) you can’t just lose the entire complement of a chromosome and b) the only plausible mechanism of reducing the number of chromosomes without deletion is by fusion. This is completely accurate. The mechanisms you’ve suggested are not plausible. They are ‘possible’ in the vague sense that it is ‘possible’ that every particle of my body could simultaneously shift a meter to the left. Which is to say physics allows for it, but if you think it is going to happen you don’t understand the subject matter.
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see here (1:00):
and as we seen above: its not a prediction either.
That’s what we’ve been telling you. In light of this data, the prediction of common descent is that a fusion occurred. I’ve spelled this out to you at length, twice.
Here:
That’s just so obviously wrong. Please consider the context that, if humans are to share common ancestry with our closest primate relatives, given that we do not have equal numbers of chromosomes, the hypothesis of common ancestry demands that either we or our closest relatives must have evolved a different number of chromosomes.
Given that humans stand out from the rest by having fewer chromosomes, the most probable explanation is that humans must have somehow evolved fewer chromosomes after we split off from the most recent common ancestor shared with chimpanzees. One way this can happen is by chromosomal fusion. A chromosomal fusion is thus a prediction of common ancestry, and that is what we find.
Do you understand this argument? Not believe, or accept, but do you at least understand it?
There is a hypothesis that demands a particular thing to have happened in order to make sense of the data. The creationism hypothesis does not demand that ancestral humans started out with 48 chromosomes like other apes, we could have been created with 46.
And here:
There is no evidence that merits the hypothesis that humans gradually lost two chromosomes by having all the adaptive and essential genes moved to other chromosomes. Instead what we have evidence for is that two chromosomes fused.
But yes, translocation of genes from one chromosome to another is one way in which a chromosome can be gradually lost. But in the absence of such evidence, and given the high levels of similarity between the fused human chromosomes and unfused chimpanzee, gorilla, orangutan(and so on) chromosomes, the evidence supports and is best explained by chromosomal fusion on the human lineage.
And I even pointed it out when I responded to John Harshman who charitably defended your position by saying that common descent does not predict a chromosome fusion in humans:
I see what you mean, but the truth of that statement actually depends in part on how much background knowledge we include when considering the hypothesis of common descent.
In total ignorance of chromosome numbers from any species, common descent predicts nothing about the number, or changes in numbers of chromosomes, nor anything about how they would or even could change. Thus finding any particular number of chromosomes in some species is neither evidence for or against common descent if we know nothing about it.
It is only in the context of knowledge of differences among the numbers of chromosomes between related species, and additional information about the mechanism of inheritance (and I gather, also, evidence from similarities in chromosome bands between chromosomes from different species), that common descent entails that a fusion took place. Only when this background knowledge is included does a chromosomal fusion become evidence for common descent, beyond it’s absence merely constituting a potential falsification.
But that door swings both ways also. Differences in the number of chromosomes only becomes a potential falsification of common descent in the context of knowledge that implies either that there is no way for the number of chromosomes to change (because there is no mechanism for it), or that such changes would be overwhelmingly more likely to be strongly deleterious.
Yeah he’s stating something not exactly correct, because there are other possible options. It would however be idiotic to think he’s not aware of that. It’s typical for this kind of popular-level exposition of science that all the technical aspects of an argument aren’t being laid out, because that would just make everyone but those of us who like the technicalities turn the channel.
Ken Miller would have to sit there and spell out the logic that given evidence for the similarity between chromosomes in all the great apes, and the fact that it is only humans that stand out from the rest of the great apes by having fewer chromosomes, and that there is no evidence for the gradual loss or translocation of individual genes to other chromosomes, only then is chromosomal fusion the only “possible” option.
Of course, even speaking about possibilities is strictly speaking incorrect, because it’s also logically possible we’re in the Matrix and chromosomes don’t even exist. Are you going to complain about that next? How about invoking the possibility that all pictures taken of great ape chromosomes are just accidental byproducts of the reflection of light on dirty microscope lenses? I mean that’s also possible, so Ken Miller is wrong.
Now can you take a break from this galactic level of volitional obtuseness you’re exhibiting?
Yes it is still a prediction of common descent, given the evidence that the other great apes have more chromosomes, and the high degree of similarity between the chromosomes that we have. In light of this evidence, common descent predicts that the larger human chromosome 2 result from a fusion of two smaller chromosomes.
And no, creationism does not predict that this should have occurred even in light of the evidence for the high degree of similarity in the G banding patterns because they could have simply been created to appear similar to begin with, there is no necessity that ancestral humans had more chromosomes that fused. You can account for it in ad-hoc fashion, but merely observing the similarity in the banding patterns does not demand that somewhere on the ancestral human lineage, two chromosomes fused. They could still just have been created that way. This goes for any and all conceivable observations. God, being able to do anything and with inscrutable motives, could have faked any and all evidence.
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i also bring up the option of ancestor with 46 chromosomes. but first you need to show that it was indeed a prediction of evolution theory.
im not sure about me, but im pretty sure about you.
by looking at the chromosomes of course. here is again the overlap between the chimp and human chromosomes:
we can clearly see that the genes are still there.
Where have we seen that?
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Maintenance of genetic complement is the prediction of evolutionary theory. Fusion is the only plausible mechanism to achieve that, so evolutionary theory predicts fusion. This has been explained to you repeatedly, continuing to deny or ignore obvious statements is dishonest.
While this accomplishes the actual prediction (maintenance of gene complement), it is several orders of magnitude less likely, as it would require exactly one fission event per lineage for 3/4 of the great ape lineages (which is already far less likely than a single fusion event in a single lineage), and that these independent fission events produce approximately homologous chromosomes based on relative size and centromere positioning (which is so ludicrously improbable that it can be dismissed without a proposed mechanism).
Again, you’re talking about something ‘possible’ in the same way it is ‘possible’ the atoms of my coffee cup could undergo spontaneous fusion. That is: never going to happen.
I’ve already told you that diagram does not show that all the genes are still there unless you accept common ancestry.
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Indeed. I’d love to hear @scd’s explanation of how a comparison to the chimp genome can demonstrate which genes have been gained and lost over the history of the human species if one rejects common ancestry.
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but ID predict the same in that case, since the genes are not missing.
not in this case. since we see that the genes which overlap with chimp genes are there- we can conclude that a fusion happened in the human lineage.
thanks.
he could just say that one of the options is a fusion, or that fusion is the most probable option. but he didnt. so you can only come up with complaints to prof Miller.
why not? if we know that the rest of the genome is almost identical, and we see that chromosome 2 overlap with the chimp chromosomes, a fusion is the most probable explanation, even under the creation scenario.
see above. we can clearly see that the two chromosomes overlap each other. so their content overlap too.
No, under the creation scenario the most probable option is that God just created the chromosome to look like a fusion, just like he created the whole genome to look as if it was related to a chimp genome.
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So you’re just willfully ignoring the explanation I already gave you for why that isn’t true?
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Please spell out your reasoning here, in as much detail as you can.
Be sure NOT to include any reference to common ancestry between humans and chimps, since that is what you are denying.
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No, it doesn’t predict that. ID could just say that humans were created with one big chromosome that was similar to two chimpanzee chromosomes laid end-to-end. ID does not predict that two human chromosomes fused. It is only on a hypothesis that has more chromosomes as an ancestral state that a fusion is predicted given the similarity to other related species.
Look, I’m getting very tired of having to explain this over and over again. You clearly don’t get it and I’m starting to doubt you’re able to.
What does the chimp genes have to do with anything on ID-creationism? You think they’re independent creations, so why are the chimp chromosomes relevant at all?
Because of the sentence you quote, all over again. Here let me copy-paste it from the quote of myself you did: because they could have simply been created to appear similar to begin with
Let me make it more obvious. “because they could have simply been created to appear similar to begin with”. Is the sentence visible to you now? Does it compute?
What does chimpanzee chromosomes have to do with human chromosomes on creationism? Aren’t they supposed to be independent creations? Can’t God simply create one long human chromosome to begin with, that simply looks similar to two chimp chromosomes laid end-to-end?
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Importantly, these created chromosomes may be homologous in terms of banding, but have no shared gene content under a design hypothesis. The inference of shared gene content from banding homology requires common descent.
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