Excellent point. But it wasn't just creationists who have considered
this -- it was in fact, first proposed by biologists. The question
asked was: Do the mitochondria and chloroplasts appear derived from
the eukaryotic line or a prokaryotic line? Resolving that question
has occupied some researchers for at least the past three decades,
and seems to have been reaching a consensus within the last fifteen
years or so.
Has convergence been tested and can it be generally identified?
Yes, I think so. While few or no traits are "perfect" markers
in all cases, studies of known cases of convergence show that the
consideration of multiple traits resolves most issues. Thanks
to the advances in molecular biology, we have additional, relatively
independent means of comparisons. Personally, I wish I knew more
about the day-to-day working details of the techniques myself.
Somewhere in a bookshelf at home I've got, _Phylogenetic patterns and
the evolutionary process: method and theory in comparative biology_
by Niles Eldredge and Joel Cracraft (New York: Columbia University
Press, 1980) -- which I keep telling myself to read -- and _Molecular
markers, natural history and evolution_ by John C. Avise (New York:
Chapman & Hall, 1994), of which I've actually managed to finish the
interesting parts. At least with respect to oxygenic photosynthesis
it appears that even bacteria were only able to come up with it once.
Given that, the number of similar components to bacteria, and the
biochemical and molecular similarities, it's been nearly impossible
to build a case for eukaryotic origins of the mitochondria and
chloroplasts. Non-creationists have seriously tried.
[...]
>Arthur Koestler points out in a section headed "The Doppelgangers"
>that some animals are amazingly alike, yet are only distantly related:
>
[Koestler writes:...parts deleted...]
>The enigma is, why so many species produced by the independent
>evolutionary line of the marsupials are so startlingly similar
>to placentals....
Superficially perhaps? For example, if these animals were amazingly
alike, how did he know that they were distantly related? Somebody
must have found a way to distinguish the groups. Convergences
can normally be determined by deeper examination of a trait and by
analysis of other ones.
>As a Progressive Creationist, I do not rule out that eukaryotic
>organelles may have had a common bacterial ancestor - an Intelligent
>Designer could have used pre-existing genetic material to create a new
>vertical step in the order of life.
Yes, endosymbiotic theory does not rule out PC.
>But neither do I accept uncritically evolutionary "just-so" stories
>which assume evolution in order to prove evolution. If naturalistic
>evolution is simply assumed apriori to be a fact, then by definition
>the *only* theories that may be proposed to explain endosymbiosis
>*must* be naturalistic evolutionary ones. Therefore they will all,
>to a greater or lesser extent, "prove" naturalistic evolution.
I'm more of a methodological naturalist than a philosophical one.
Then again, I'm a bit set in my ways and would need a pretty good
set of examples to drop naturalism as a working hypothesis of first
choice.
Regards, Tim Ikeda (timi@mendel.berkeley.edu)