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Author Topic:   Problems w/ the Current ToE
Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 7 of 13 (243)
03-16-2001 11:16 AM
Reply to: Message 3 by Thmsberry
03-15-2001 6:04 AM


Hi Thmsberry,
quote:
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?

You've stated things a bit unequivocally ("all current evidence etc...").
First, they're not scientific facts but informed hypotheses.
Second, in the general case, members of the same species can be assumed to have a common ancestor. When this is not the case it means the same species evolved more than once. This is probably only possible in any meaningful sense for single-celled organisms, and all it would mean is that the same or very similar genetic accidents happened more than once, resulting in organisms with equivalent genomes. I'm speculating, since I've never myself read of anyone seriously entertaining this possibility, but that doesn't mean anything.
One of the views receiving attention these days is that gene sharing was very common among early life, and this is described in some detail in an article (that I referenced once before, and I see Larry mentions it, too) titled Uprooting the Tree of Life by W. Ford Doolittle that appeared in the February, 2000, issue of Scientific American, and here's a diagram from that article (click to enlarge):
We've already discussed that BSC is mostly appropriate only for the more complex lifeforms like mammals, and so it certainly shouldn't be applied to a situation like that represented above involving single-celled organisms. Species distinctions can be more difficult to make when organisms are single-celled and similar, but the DNA tells the truth. We can certainly make no specific species distinctions about postulated evolutionary ancestors, but the above diagram derives from DNA analysis of modern organisms. It is speculative, and if that's a synonym for "ridiculously ambiguous" then fine. It's certainly also unprovable, as is all science, but it does have evidentiary support based on DNA and so definitely is not "basically meaningless."
quote:
Asexual organisms alone have an ambiguous species definition. Add to that the fact that Archae show no consistent correlations between morphology and known phylogeny and their phylogenies even intersect with organisms of other domains. Thus, How would it ever even be possible to determine if the early live ancestors(as in a population) were of the same species?

I think you mistake what is being attempted. It is understood that we can't know what the specific ancestors were, but we can certainly draw hypotheses concerning possible scenarios. Current work is identifying and characterizing the reasonable possibilities indicated by the evidence available, that is all. But it is understood that there can never be any definitive evolutionary tree because there is simply insufficient evidence. Time has destroyed most of the evidence, and scientists just have to make do with what's left.
quote:
If the first population of life contained multiple kingdoms. Such as the diversity in Archae and Eubacteria currently shows. and If this diversity does not fit in a nested hierarchy that corelates to the genetic diversity. As the diversity in the Archae and Eubacteria currently shows. Then the first population was not one species. It wasn't even monophyletic.

By the time you wrote this Larry had already referenced you to Doolittle. It is already well understood that early life might not fit a neatly nested hierarchy.
quote:
This basically leaves the premise that all life on this planet can be traced in part to a population of a single domain.
Thus, the individual organism and/or species idea is not a supported one. And this is one of the major aspects of the current ToE.

The ToE is just a framework of understanding that unites Darwinian concepts like descent with modification and natural selection with a genetic foundation. The ToE never axiomatically held that all life descends from a single original cell. That's just a once-common perspective that fit within the framework of the theory, as do the newer perspectives on this topic. It was not a major aspect of the theory, but rather just a possibility permitted within the framework of the theory.
The possibility of all modern life descending from a single cell is consistent with the ToE. So is the possibility of all modern life descending from a community of gene-sharing cells. Changing preferences within the scientific community for one over the other do not require any change to the encompassing theory.
--Percy

This message is a reply to:
 Message 3 by Thmsberry, posted 03-15-2001 6:04 AM Thmsberry has replied

Replies to this message:
 Message 8 by Thmsberry, posted 03-16-2001 12:39 PM Percy has replied

Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 10 of 13 (246)
03-16-2001 3:20 PM
Reply to: Message 8 by Thmsberry
03-16-2001 12:39 PM


Hi Thmsberry,
quote:
But then you end with the typical Darwinian rhetoric that it is possible that all life stemmed from one ancestral cell.

I'm sorry if I wasn't clear. This isn't true. My views are strongly influenced by what I read. I found Doolittle's article in the February, 2000, issue of Scientific American, a diagram from which is included in my previous post, very persuasive. All that means is that given the information I'm aware of today, his is the explanation I find most acceptable. I consider his explanation tentative and subject to future revision and even refutation.
You are confusing specific perspectives within the ToE with the ToE itself. We just discussed the definition of the Modern Synthesis in detail in another thread. Both a single-cell origin and a multi-cell gene-sharing origin for modern life fit within the ToE. Your view seems to be that if a perspective is described in most books available today that it makes that view somehow fundamental to the theory. It doesn't. It just means it is, or was, a widely held view, nothing more.
quote:
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.

What would it prove if I could or couldn't? You've already been given two references to articles representing that modern life may have originated from a community of gene-sharing cells. I don't know if the authors of these articles have written "popular reputable textbooks", but what does it matter given the references you already have? Reputable scientists are seriously exploring polyphyletic possibilities. Just the fact that you know about these possibilities means that you've read about them somewhere, so you of course know of other sources of this information than the ones we've given you. What do you care whether these views have yet made it into textbooks?
As it happens, Evolution, Third Edition (by Monroe W. Strickberger, 2000, Jones and Bartlett) not only mentions just such a possible scenario, but even has a diagram of a possible scenario for symbiotic evolution on page 181 (click to enlarge):
--Percy
[This message has been edited by Percipient (edited 03-16-2001).]

This message is a reply to:
 Message 8 by Thmsberry, posted 03-16-2001 12:39 PM Thmsberry has replied

Replies to this message:
 Message 11 by Thmsberry, posted 03-17-2001 3:48 AM Percy has replied

Percy
Member
Posts: 22392
From: New Hampshire
Joined: 12-23-2000
Member Rating: 5.2


Message 12 of 13 (250)
03-17-2001 10:30 AM
Reply to: Message 11 by Thmsberry
03-17-2001 3:48 AM


Hi Thmsberry,
quote:
The current ToE is suppose to be an explanation for the Biodiversity on this planet. Yet a paraphyletic community of sharing cells model has life already starting with Biodiversity, so the theory can no longer be seen as an explantation for life's biodiversity. It becomes a partial explanation at best.

You seem determined to maintain the most odd view of theories I've ever encountered. Theories are never complete, and all theories are partial, simply because of the principle of tentativity. Scientists work to extend and expand theories. Sometimes a theoretical framework can't accommodate new discoveries, and then a new theory must be developed to replace the old.
I don't want to argue whether you're right or wrong about the ToE providing an incomplete explanation for biodiversity. As you trace further and further back in time you get more and more out of the realm of the ToE and into issues related to the origin of life. There are no hard and fast rules for drawing the boundary between these two areas.
If you decide that this particular point in the history of life belongs within the ToE, and that the ToE doesn't provide a satisfactory explanation for it, then that does mean the ToE is incomplete, but only in the sense I mentioned above that all theories are incomplete.
quote:
Also, the older the population of organisms that scientist examine the greater their biodiversity. Which would indicate that the greatest amount of biodiversity occurs the closer you get to the ancestral paraphyletic community. So while life is indeed changing over time. The greatest type of diversity existed in the initial community, and thus life has not become increasingly diverse. Another premise of the current ToE.

I'm sure this isn't true. For one thing, there are more species alive today on the planet than at any time in its history.
quote:
In addition, accepting horizontal mechanisms does not allow for the idea that commonality in organismal genomes indicate a live ancestral relationships. A paraphyletic community of sharing cells do not share a common live ancestor. They share a common dead ancestor, namely common DNA or RNA sequences.

The ToE includes genetic mechanisms, and so is inclusive of explanations concerning ancestral relationships based upon DNA/RNA sharing.
quote:
The true explanation of life's biodiversity appears to occur at some sort of stage of symbiosis between a community of Prebionts. This would explain why a community of paryphyletic cells would have emerged in the first place. A stage that is extemely speculative and the current ToE by definition can never examine.

But you have an odd definition of the ToE, one that not only isn't shared by others here, but also not by scientists working in this area, since they seem to believe they're operating within the framework of the ToE. It would make things a lot easier if you would accept the definitions the scientific community agrees upon.
I don't know if this helps, but from where I sit it looks like you're telling everyone else that if they squint and look sideways things will look the same to us as they do to you. No one but you sees any reason to do this.
--Percy

This message is a reply to:
 Message 11 by Thmsberry, posted 03-17-2001 3:48 AM Thmsberry has not replied

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