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Swingin’ from the chandeliers retro: Rick Sternberg on human-chimp genome similarity


Following up on “Maybe Carl Zimmer is free to read Science and Human Origins now …”, someone has reminded us of a 2009 Evolution News & Views post by Biologic Institute’s Rick Sternberg, “Guy Walks Into a Bar and Thinks He’s a Chimpanzee: The Unbearable Lightness of Chimp-Human Genome Similarity” (May14),
where he describes dealing with a barstool boreTM on human-chimp genome similarity,

Here is an example of how “chats” like the one I’m talking about begin. After I have been formally introduced (though sometimes not) to an emissary of enlightenment, my just-made acquaintance proceeds to ask whether I’ve read a certain book (title withheld) that purportedly shows four things: We are 99% chimp; our chromosomes contain “scars” that are shared with those of our simian cousins; the DNA scars, like 98.5% of our genome, are simply junk; and these facts change everything we “know” about God. In response I invariably say, “How interesting,” with a wan smile followed by, “Oh, sure, I’ve read parts of it.” For me this is a taxing turn in the conversation for I must all at once feign attention, ask the bartender for another drink, and work to suppress my desire to bolt out the door. Sensing my unease, my new friend usually seems to read my restlessness as one of intellectual discomfort — possibly fear. Anyhow, seeing me as the quarry, he leans in and expounds on each of the topics, his eyes glinting throughout with the impression that he is surrounding me via a four-pronged conceptual assault, a two-pincer strategy. (All the while, I am praising the heavenly host for the warm irreducible complexity of scotch.)

Eventually, Sternberg decides to respond, instead of pretending to have spotted a friend across the street:

“I try to outline all the functions of telomeric repeats, but my friend tells me that I am getting off the subject.

“He wants to me to focus on the ITSs, the tracks of the hexamer TTAGGG that reside within chromosome arms or around the centromere, not at the ends. I tell him that I was just coming to that topic. The story, you see, is that in the lineage leading up (or down, I forget which) to chimps and humans, a fusion of chromosome ends occurred — two telomeres became stuck together, the DNA was stitched together, and now we find the remnants of this event on the inside of chromosomes. And to be fair, I concede at this point that the 2q13 ITS site shared by chimps and humans can be considered a synapomorphy, a five-dollar cladistic term meaning a genetic marker that the two species share. As this is said, it is apparent that the countenance of my acquaintance lightens a bit only to darken a second later. For I follow up by saying that of all the known ITSs, and there are many in the genomes of chimps and humans, as well as mice and rats and cows…, the 2q13 ITS is the only one that can be associated with an evolutionary breakpoint or fusion.

The other ITSs, I hasten to add, do not square up with chromosomal breakpoints in primates (Farré M, Ponsà M, Bosch M. 2009, “Interstitial telomeric sequences (ITSs) are not located at the exact evolutionary breakpoints in primates,” Cytogenetic and Genome Research 124(2): 128-131.).

In brief, to hone in on the 2q13 ITS as being typical of what we see in the human and chimp genomes seems almost like cherry-picking data. Most are not DNA scars in the way they have been portrayed.”

With what results, go here to see.

In fairness, barroom bores are preferable to lecture room bores because the most they can ruin is a quiet moment. Sternberg should know.


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