update on Human-orangutan origins

Richard.Zander at MOBOT.ORG Richard.Zander at MOBOT.ORG
Wed Apr 28 13:51:25 CDT 2004


The orang controversy has raised an interesting question. There is a
horrible article at:

http://www.pnas.org/cgi/reprint/97/9/5003.pdf

titled "How reliable are human phylogenetic hypotheses?" This article
compares cladograms of data based on morphology and those based on molecular
information. It found that both results are well supported.

(The authors choose the molecular results because the morphological results
must be "false." No, really, check it out. The logic is amazing on how they
decided on this.)

In any case, suppose we have two well-supported but different cladograms.
The molecular one says ((((Homo Pan)Gorilla)Pongo)Hylobates).
The morphological one says ((((Gorilla Pongo)Pan)Homo)Hylobates).

Now the data supporting one is evidence against the rationale supporting the
other. So if the molecular cladogram is correct, then the morphological one
must be explained away, such as "tons of morphological information probably
include lots of features that are genetically the same or are inherited as a
block, and therefore weight the data falsely which inflates the bootstrap."
I rather like that explanation.

If the morphological cladogram is correct (and we humans are primitive
though neotenic, therefore the unrelated orangs as advanced must be
throwbacks in some way), we have to explain away the molecular data as . . .
what? Concerted lineage sorting of a really heavy sort?

Suppose both cladograms were correct. This would then be evidence for two
(2) systems of saving phylogenetic information in the genome. How would it
save two (2) different sets of information? Could there be an adaptive
advantage to saving two sets of (conflicting) information about what
ancestors begat the taxon? If we are primitive, did we invent (canalize,
orthoevolution) chimp genes for some reason?

Okay, science fiction.

______________________
Richard H. Zander
Bryology Group
Missouri Botanical Garden
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