Humans and orangutans

[John Grehan]

>Stephen Manning wrote
>I believe morphological and molecular data are complementary.  When and if
>they conflict my hypothesis would usually be that the molecular genetics
>is more reliable, statistically, unless there is some particular factor
>that would tend to negate this.  For example, if there is good enough
>reason to believe that a particular morphological trait is highly selected
>for or against in the context of the particular environment or biological
>community in which the organism bearing the trait probably existed, that
>should lead to less reliance on the morphology than one might otherwise
>accord it.

This probably reflects the general view taken by primatologists - that
somehow genetic similarity does not involve genes connected with the
environment (so that morphological features are unreliable as they may
involve shared characters arising independently of phylogeny while genetic
similarity apparently does not include genes that have been selected by
this process). Thus, the 35 human-orangutan synapomorphies are dismissed
out of hand (and that's not overstating the reaction) by primate molecular
geneticists and morphologists alike. And this is not to even raise the
question of how much of a role natural selection has in long-term genetic
structure with jumping genes, gene duplication through unequal crossover,
biased gene conversion and other molecular genetic turnover mechanisms also
running amok among species genomes.

>   So at least superficially the morphological record would be misleading
> compared to the molecular one that showed only one or two mutations
> separated the taxa.  Etc...

This appears to be a similar perspective to that raised earlier by Ken
Kinman. It is possible that any number of morphological synapomorphies may
be correlated with a smaller number of genetic changes so that the 35
morphologies may be 15 genes. At present this is only a 'maybe' for human
origins so whether or not the number of genetic synapomorphies correlated
with morphological synapomorphies gives one or other phylogeny seems to lie
in the future. It seems to me to be a corollary to the current problem of
genetic similarity analysis not being able to designate only shared derived
states prior to analysis.

>I really think in the future, when people are not only able to recognize
>base sequences but also identify the functions, if any, of the particular
>genes being sequenced, we will be in a much better position to evaluate
>reliably how accurate phylogenetic conclusions from morphology are in the
>absence of supporting molecular data; or whether conclusions based on
>molecular data are more accurate than those based on morphological data
>when the two conflict.  That may not be in our lifetimes.

And this again presupposes that functions arise only arise through natural
selection.

John Grehan

Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
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