Problems w/ the Current ToE

1) there is a debate over whether or not there is a single universal ancestor or several ancestors so the line in Futuyma is a bit presumptuous. Of course it is several years old and well before Doolittle's work.2) The only challenge you present here is that a single ancestor doesn't fit this definition. If there was a single ancestor as soon as it reproduced a population took over and we have consistency.Cheers,
Larry Handli

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Originally posted by Thmsberry:

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If you believe that only one live organism was the ancestor of all life, what type of scientific evidence can possibly support this conclusion?

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The only manner this could be confirmed is through a genetic marker or something. I doubt that is possible.

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If you accept the view of several live ancestors, what is the proposed genetic variation amongst these live ancestors?

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I'd reference you to Doolittle's article in Scientific American and his cited works there. This is a bit beyond me.

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I have read that those who support several live ancestors make the assumption that they are all members of the same species. Yet, all current evidence points to the fact that the oldest known live organisms on this planet reproduce asexually. In addition, all current evidence points to the fact that the oldest known live organisms were without a nucleus. Doesn't these scientific facts make the idea that they were all of the same species ridiculously ambiguous and basically meaningless and unprovable?

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If they were virtually identical, not really. Given no genetic evidence you would have to rely on morphology and you wouldn't be using the reproduction standard. Again, I'm not sure why this is a particular problem. Labeling them the same species or not seems to be more of a semantic argument given the probably state of the Earth at the time.Larry

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Morphological similarity amongst organisms in the domain of known Archae does not correlate to a species level of differentiation. They relate more to the phylum level. And for the oldest Kingdom Archae, considered to be the closest known thing to this common ancestor it is currently impossible to even test its morphology.

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This is not a settled issue. Indeed, recent arguments are disputing that that Archea evolved from eukaryotic root due to high genetic similarities inferred from complete genome analysis between Archaebacteria and Eubacteria inferred from complete genome analysis. . See:Herv Philippe, Patrick Forterre. The Rooting of the Universal Tree of Life Is Not Reliable. Journal Of Molecular Evolution. 49, 509 (1999). They argue for a eukaryotic ancestor and provide several reasons why. They specifically take issue with previous attempts to create a tree of life [QUOTE][b]
Furthermore, the addition of new sequences to data sets has often turned apparently reasonable phylogenies into confused ones. We have thus revisited all composite protein trees that have been used to root the universal tree of life up to now (elongation factors, ATPases, tRNA synthetases, carbamoyl phosphate synthetases, signal recognition particle proteins) with updated data sets. In general, the two prokaryotic domains were not monophyletic with several aberrant groupings at different levels of the tree. Furthermore, the respective phylogenies contradicted each others, so that various ad hoc scenarios (paralogy or lateral gene transfer) must be proposed in order to obtain the traditional Archaebacteria-Eukaryota sisterhood. More importantly, all of the markers are heavily saturated with respect to amino acid substitutions. As phylogenies inferred from saturated data sets are extremely sensitive to differences in evolutionary rates, present phylogenies used to root the universal tree of life could be biased by the phenomenon of long branch attraction. [/QUOTE][/b]You may access some of the work done in the area at a conference that addresses many of these issues at: LesTreilles_e.The essential reasons for inferring a single common ancestor whether several of one species one organism comes from the observations: http://www.mines.unr.edu/able/GEOL100-11/tsld010.htm
Taken from a lower level course, but a nice summary is there.Could the inference be wrong? Sure, but given the uncertainty of the actual tree of life and those 5 factors, it is still a quite viable hypothesis. At most, even if it is wrong, evolution still holds back a couple billion years.

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[This message has been edited by Percipient (edited 03-19-2001).]

from thmsberry:

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Can you list some popular reputable textbook that states that all life emerged from a paraphyletic community of gene sharing cells? A possibility that is more consistent with the actual evidence.

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The Doolittle reference specifically does says it is possible. And it is based on articles like the one I cited in my last message as well as other articles by Ford W. Doolittle. Additionally, it seems making as strong of a claim as you want would be making the same mistake your cited source does except in reverse.Many texts may say exactly what you are saying they do and they are overstating the claim if they do. I don't believe that Futuyma takes a strong position in his book one way or another (meaning I could have missed it somewhere) but he certainly doesn't hold it as a central element as you claim the ToE does universally. Secondly, texts aren't always the best source for accurate and especially up to date information. Researchers are often at odds with texts because texts aren't updated frequently enough or are just inaccurate. In this case, you have been offered specific citations from recent research. Essentially, your argument would boil down to a lot of texts are bad. I agree, and as I review texts in social science quite freqently, this is only the tip of the iceberg.Talkorigins.org certainly oversimplifies the issue in certain FAQs and several on talk.origins have complained about that. The problem is all writers are volunteers and don't have time to constantly update it. I'll mention it on talk.origins next time the issue comes up.Larry