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Orangs, Humans & ERVs

July 6, 2009

Last week I briefly posted on the claim being made by John Grehan and Jeffrey Schwartz that morphological evidence indicates that the orang is our closest living relative and that molecular evidence accumulated over the past 40 years that the chimpanzee is closer is flawed and can be discarded. A vigorous discussion ensued and is still ongoing.

Last night I posted a question that remains unanswered by the proponents of the orang claim, so I’m going to repeat it here in a little more detail to see what we can ascertain. As a starter, let’s allow the claim that the molecular methods that support the Homo-Pan clade are flawed and should be discarded. How does a supporter of the Homo-Pongo clade explain the distribution of endogenous retroviruses within the great apes, a distribution that would appear to support the closer affinity of Homo and Pan.

retrovirus.gif

(Source: Lebedev, Y. B., Belonovitch, O. S., Zybrova, N. V, Khil, P. P., Kurdyukov, S. G., Vinogradova, T. V., Hunsmann, G., and Sverdlov, E. D. 2000 “Differences in HERV-K LTR insertions in orthologous loci of humans and great apes.” Gene 247: 265-277.)

Now it would appear (to me at least) that these results which are not dependent on the methods criticized by Grehan and Schwartz would unambiguously offer support for the Pan-Homo clade (and indeed the molecular phylogenies that they discard).

Thoughts?

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  1. July 6, 2009 at 5:06 pm

    And what about Alu inserts, which tell a similar tale: http://www.pnas.org/content/100/22/12787.abstract

  2. July 6, 2009 at 5:16 pm

    Indeed Carl. I had forgotten about those.

  3. July 7, 2009 at 7:22 am

    Does that diagram not support monophyly of African great apes and humans, rather than a Pan-Homo clade?

    Sorry to be a pedant.

  4. July 7, 2009 at 11:29 am

    Yes, but the point here is that it would offer evidence for Pan-Homo over Pongo-Homo (the former being more parsimonious).

  5. July 10, 2009 at 1:43 pm

    I find it interesting that I’ve drawn Grehan’s attention to my question not once, but twice, in the original thread (where he has been active) and he hasn’t addressed the issue.

    Just sayin’

  6. July 13, 2009 at 11:54 am

    Over in the other thread Grehan has finally replied (ignoring my request to move discussion of the erv evidence over here). Quoth he:

    Are these ltr ervs uniquely identical or do they share unique base substitutions?

    By the way, none of the ltr’s listed in this paper support a human-chimp clade.

    I’ll let him explain why he thinks the first point is important. Regarding the second one: the point is that they don’t support a Pongo-Homo clade that would exclude Pan and/or Gorilla as being closer to Homo.

    And then there is the Alu evidence that Carl raises above.

    We might as well face it. The clear preponderance of evidence collected over the past 40 years is for Pan-Homo and not Pongo-Homo. Grehan thinks otherwise but I suspect that nothing is going to change his mind.

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