Chromosome Fusion in Humans - or Not?

Since phylogeny thread went off-topic because of me, I’ll copy in some responses here. I’m not going to defend the argument against chromosome fusion. I do not know enough about it. But if you want to critique the argument I listened to, feel free. I’ll read the responses.

I’ve only listened to Georgia Purdom weeks ago. Not something I’ve researched. She references Tomkins though.

I’ve set it at the time stamp. Listen until about 28 minutes. So 8 minutes long.

My question is - is there an explanation of when this happened? Would it happen it one hominid first? And then be passed down until selected for? Obviously it has to happen in both sexes? I guess my questions are more pragmatic that way :slight_smile: If it’s happened in other animals like zebra crosses and it’s been observed - I suppose that would answer those questions. So if anyone has a link to that explanation on my kind of level, it’d be appreciated. Thanks, I’m curious.

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Dave Wisker posted an excellent series on The Pandas Thumb that went over this:

Part 1
Part 2
Part 3

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I skimmed those. I’m not sure my brain on nausea :joy: can handle looking up all the terms I don’t know in order to understand those articles right now. But I’m sure I’ll want to come back to it some day if not soon. I love the archive for that purpose.

The fusion would happen in one individual, or actually in the sperm or egg that resulted in that individual. That first person would therefore have been heterozygotic, with one fused chromosome and one pair of unfused ones. Because acrocentric fusions don’t interfere much with fertility, the mutation would probably have been fixed by drift, not selection, all of that one original mutation. No extra mutations are needed.

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Pictures may help.

Chromosomal banding patterns line up for a chromosomal fusion:

Artistic render:
image

Actual chromosomes:
image

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Okay, but remember: You asked for it…

20:24 Odd that so much vitriol is put on the fact that evolution makes a strong prediction. Making strong predictions is good. We have 23, chimps have 24, either the ancestral state was 23 with a fission or it was 24 with a fusion. Since all other apes (not just chimps) are 24, the parsimonious explanation is a fusion in the human lineage. This is a strong prediction.

20:50 And match the vitriol of a strong prediction with a dismissive treatment of the strong support for that prediction. Alignment of banding patterns is non-trivial, and finding two chimpanzee chromosomes with banding patterns that align with either side of one of the longest human chromosomes is exactly what you should find if there was a fusion. In fairness, this would also be compatible with a fission, but this is again not parsimonious given the other species.

21:10 And now the dishonesty starts! Remarkable given she contradicts her own presentation of the material thus far. She claims here that the ‘story’ was developed after finding the alignment of banding patterns, when the reverse is true! First we recognized that there was a difference in chromosome complement between humans and other apes, then we predicted a fusion in the human lineage (with a possible but unlikely fission) which would result in shared patterns between two chimp chromosomes and a single human chromosome, then we found exactly that thing we predicted. And again, banding alignment is non-trivial. You don’t find high quality alignments in banding patterns just anywhere.

21:50 Funny she mentions you can’t go into the fossils to find this, an admission that evidence from fossils is valid, because she ignores the fossil evidence. Don’t know how that works, but not relevant to the content.

22:07 Anyone who calls anything ‘definitive proof’ of anything is doing bad science. It is extremely strong supportive evidence of a fusion in the human lineage, which explains the difference in chromosome complement between humans and other great apes. Point me to the person calling it definitive proof of common ancestry and I’ll happily critique their word choice.

22:14 No, that’s not what a law is, but I’m glad she accepts that science doesn’t deal in definitive proof. I’m sure that means she complains about her ‘side’ demanding definitive proof for evolution then, right? Right?

22:40 After saying that some call it definitive proof, she shows two quotes from famous scientists. Neither calls it definitive proof. Funny, that.

23:45 She basically calls Ken Miller a liar. So that’s nice.

23:48 She makes a direct claim that she can show it wasn’t a fusion. Strong claim. Let’s see what she’s got!

24:00 “Because this isn’t about the evidence. Okay? The evidence is clear. It’s about a worldview, and not wanting to change that worldview even in spite of the obvious” That light you see is Georgia projecting hard enough you should see the AIG logo on the moon.

24:34 The relabeling is a product of annotation convenience. It makes a lot of programmatic work with sequences from apes easier, so people do it. Which, by the way, it wouldn’t if there wasn’t a fusion.

25:10 ‘Telomeres prevent fusions, so we should see a BUNCH of telomeres in a fusion!’ No, Georgia, we should barely see any telomeres in a fusion, because telomeres prevent fusions. How have you gotten such a simple thing so obviously wrong? Finding telomeres isn’t a requirement of validating a fusion site anyway. Honestly not even something you’d expect to find.

25:19 ‘Every chromosome has one centromere, so we should see an inactivated centromere along with the real one’ Which is exactly what we’ve found.

25:45 She complains that the telomere findings perfectly match the actual expectations (better than perfect, actually) rather than her ludicrous expectation that is obviously impossible. O…kay.

25:51 She mentions that there are ‘some’ telomeres there, and fails to mention that the number there is many orders of magnitude more than what you’d otherwise expect outside of a subtelomeric region.

26:03 Yes, we would admit that the telomere sequences we find are degenerate. Like what we find in subtelomeric regions. Because if there were functional telomeres there wouldn’t have been a fusion! I honestly have difficulty understanding how someone can not get this.

26:13 She says there shouldn’t be any telomere sequences that are there because it’s not two chromosomes that have fused. Ignoring the fact that there are telomeres there. A lot of them. Something that isn’t needed for it to be a fusion, but completely invalidates the idea it wasn’t. So yeah, obvious contradiction of her own point.

26:25 Again, she admits that we actually do find evidence of a centromere. Not an active one, obviously, we wouldn’t expect that. So again, we find exactly what we’d predict, but she dismisses it for… reasons.

26:40 Alphoid sequences aren’t unique to centromeres in the same way that telomeric sequences aren’t unique to telomeres. Hopefully the reason that’s an unimpressive argument is obvious. Can you guess how many non centromeric alphoid sequences are found in the human karyotype? Hint: It is a very small number.

26:42 She hand-waves to Tomkins. I’ve spent several hundred hours going through Tomkins’ work. It is all very bad. I’ll address any she does, or otherwise upon request.

26:49 ‘Gene spans the fusion site!’ A weird transcript of a pseudogene spans the fusion site. The variant in question is expressed at the level of noise, and has low similarity to the ‘highly’ transcribed variants (which are still barely transcribed). And that pseudogene is found multiple places throughout the genome, exclusively at telomeres. Yeah, push that thread, it’ll help.

And by the way, even if it was confirmed to be an actual gene with actual function, it still wouldn’t disprove a fusion. The entire line of evidence is completely irrelevant to Tomkins’ thesis at best, and absolutely contradictory to it at worst. Really, push that thread.

27:43 She claims that it doesn’t match up ‘sequence-wise’ with Ptr12&13. This is an outright lie. There is no way around it. But don’t just take my word for it:

Lines up pretty well if you ask me.

And that’s the requested segment of the video. Let me know if you have any questions.

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Thanks, that was very detailed. It will help when I’m ready to understand all the biology related to this better.

There is no need for me to watch the video since she referenced Tompkins. I suspected Tompkins because he seems to be at the forefront of attempts to dispute the ancient fusion event of chromosome 2 in humans. These are some papers by Tompkins on the issue:

A bare bones response is found in this PZ Myers article below. I am citing it because it summarizes the strategy utilized by Tompkins in his attempts to deny the chromosome 2 fusion event.

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Image citation?

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http://autograph.genouest.org/
Have fun, make your own!

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Wow. Thanks.

@thoughtful I missed this initially, but saw it when @Michael_Okoko did the same:

I have it on good authority that Tomkins really hates that particular misspelling of his name.

Its a synonymous misspelling though. I don’t think it would reduce his fitness in a general context.

I made my own synteny map. Its simply beautiful:

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Clearly you’re ignoring the functional importance of the specific spelling on reminding some of really awful arguments.

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LOL. That hit me hard.

@thoughtful, this article explains the terms used in the AUTOGRAPH-derived synteny map:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://academic.oup.com/bioinformatics/article/23/4/498/180639&ved=2ahUKEwjl2Yqw-czuAhWqQhUIHTP6AgwQFjANegQIDRAB&usg=AOvVaw12clVHsfrfa5b5xPkv7jRg

Ugh. I swear I saw an incorrect spelling of his name and made sure it was correct in my reply. It must have been in another thread or a figment of my imagination…

I had to appease my conscience so I did a search of the forum and found at least two places where I did spell his name correctly.

I hate, hate typos, especially when I write them. But the worst are with names. I have co-workers who are very loose with spelling people’s names correctly and it drives me nuts. Especially when people’s names will be on agendas or…certificates! That’s just a really bad look… I try to question them if anything looks funny when I’m editing. The worst is when a person has two disparate first names - one likely official and one preferred - and you find both online and I don’t have access to the person’s email to see their email signature. :roll_eyes: Lol, I have no idea why I’m venting about this. But there you go. I care about details. :relaxed: Yes, I’m editing my original post. Names matter folks.

Yes, I often wait on pins and needles until my post is approved so I can jump in and edit it so no one but the moderators have to witness the ugliness.

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10 / 10 :+1:

So Georgia Purdom shows the initial evidence for the fusion event (the chromosome banding), ignores all the evidence found subsequently including the full genome sequences, then says:

This is not based on any evidential experience, this is just a story that they had to develop to explain this, it’s not like you can go in the fossils and find this, ok, that’s not reality, so this is just a story they’ve developed to explain it.

But it is based on evidential experience. She even cited some of that evidence.

As for her own “evidence” of it not being a fusion, she says that finding the fused teleomeres is hard, and scientists “can’t really find” the inactive centromere. But that’s not true. We have found both the teleomeres and the centromere. See for example here: “Comparative evolutionary analyses of human chromosome 2 have shown that the homolog of 2q, which fused in the human line (about 5–6 million years ago, mya), was identical in marker order and centromere position to those of chimpanzee and gorilla.”

She refers to Tomkins supposed gene straddling the fusion site, completely ignoring the possibility that that gene evolved after the fusion.* She says that while humans and chimps have DNA similarity because we are both mammals, we do not have extremely high levels of genome similarity, which is completely wrong, since the human/chimp genomes are much, much more similar than those of mammals in general.

She also seems to think scientific laws are definitive proofs, which is absurd, and bases her later arguments on “because the bible is true”.

So I’m rejecting her claims on the grounds that (i) she’s ignoring most of the available evidence and misrepresenting the bits she doesn’t ignore, and (ii) she doesn’t know what she’s talking about.

*Which seems to be the case.

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Oh, and her ‘quote’ from Parsons et al is a misquote which Google finds only on one creationist blog comment by one Rick Davis. She’s ‘quoting’ from works she hasn’t read, which completely destroys her credibility.

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