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Member (Idle past 4871 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
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Author | Topic: What's the problem with teaching ID? | |||||||||||||||||||||||
Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
Can you give an example of a functional protein that shares deep homology amongst eukaryotes which is also unnecessary? Read what I said again, then come back and ask your question:
However, I argued in that article why the front-loading hypothesis requires that eukaryotic proteins share deep homology with unnecessary but functional prokaryotic proteins. I should add that by "unnecessary" I mean a protein that is not necessary to the existence of life.
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
Err, because one model (FLH) is making a prediction, while another model (modern synthesis) is merely capable of explaining an observation. So it all boils down to whether you're an "explanationist" or a "predictionist": which one do you lend more weight to? And it's not like philosophers of science are in agreement on this - I'll grant you that.
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
If they have not then ID is not a subject worth teaching. Of course, if you had followed this thread you would know that I don't advocate the teaching of ID in school.
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
You point to proteins that have function and at the same time want to claim that they are useless. Those two things do not go together. You can have a protein that is functional but deleting it won't kill the organism, or even significantly reduce its fitness, which means it's not necessary for life. I never, ever, ever said anything about a protein that is both functional and useless. You're putting words into my mouth Taq.
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
Then FLH is making the same prediction as evolution. No. See here:Deep Homology and Front-loading | The Genome's Tale
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
Why would the LUCA have a minimal set of genes ? Wouldn't it be expected to have more than the absolute minimum ? Given evolution, rather than design. No, because the LUCA could easily have been a simple progenote (and, indeed, a number of papers have argued for this, which kinda indicates evolution doesn't predict a progenote or a non-progenote for LUCA), and, actually, the LUCA could have been a simple self-replicating molecule encoding only a few genes. A population of these self-replicators could then have branched off, eventually forming into the domains of life that we see today.
Secondly even if you could argue that the LUCA would have a minimal set of genes, don't you need to show that the genes you refer to ARE from the LUCA and AREN'T part of a minimal set or derived from a minimal set ? Yes, of course. To determine that they aren't part of a minimal set, you need to do homology comparisons.
Also, suppose that the LUCA DID have a minimal set of genes and they DID allow for the evolution of modern life as we see it. Wouldn't that be an even better argument for front-loading ? Huh? I have no idea where you're going with this.
Finally, the argument that non-teleological evolution wouldn't plan for the things we see... That's not my argument. I'm simply pointing out that the FLH makes a specific prediction which non-teleological evolution does not make. And it's not a case of "the designer wanted giraffe's" any more than evolutionary predictions are like that.
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
However, whatever it was, it would not be expected to have a minimal gene set for whatever it was, would it ? Simplicity is more an aim of design rather than evolution. Once evolution gets going we should expect more complexity than is strictly needed. Yes, but as I stated earlier, there is nothing at all stopping some early population composed of self-replicating molecules from branching off and diverging into Archaea and Bacteria - under the non-telic model. But under front-loading, you have to load the genome with functional but unnecessary proteins. FL doesn't work otherwise.
Isn't your argument that there genes going back to the LUCA which are NOT part of a minimal set ? Surely homology tests will - at most - show if the LUCA likely had a homologous gene or not ? Homology comparisons between a eukaryotic protein and a prokaryotic protein will determine if the two proteins are indeed homologous; to determine if the prokaryotic protein was part of a minimal set (i.e., that it evolved from a protein that is necessary for the existence of life), we'd need to trace the homology deeper and see if it shares any homology with proteins in prokaryotes that are needed for life (such as DNA replication machinery, etc.)
Suppose that rather than there being NO minimal gene sets that allowed for the evolution of life that we see today there were a VERY FEW - a very small proportion - that did. Wouldn't then, a LUCA with one of those gene-sets be entirely compatible with the concept of front-loading ? The issue isn't so much about whether a minimum gene set could allow the appearance of the taxa we see today. Given an initial genome that only has the most crucial proteins to life, evolution could have taken many different directions - including the direction of life forms as we see them today. However, if the front-loading designer(s) intended for a specific outcome, you'd have to load the first genomes with proteins - like globins, tubulin analogs, etc. - such that evolution would build on those proteins and the future of evolution would be shaped, and the origin of animals and plants would be much more likely. That's why you'd need to load the initial genomes with unnecessary (but functional!) proteins.
For it to be a prediction, you have to show that a minimal gene set doesn't provide the flexibility needed - especially given the time available - and you haven't done that. A minimal gene set could evolve in a plethora of directions - including plants and animals. But, speaking from a probabilistic standpoint, with just a minimal gene set, the odds of animals and plants appearing on the scene are quite low, since there are many alternatives. For example, how plausible is it that SecY (which is, IIRC, a protein essential to all life) will evolve into hemoglobin, since they are not at all nearby in sequence space, and there are a multitude of possible proteins SecY could potentially evolve into. And this means that the animals you want to appear on the scene of life will very probably not appear. However, if you load a genome with globins, then it's quite likely that some form of blood will evolve, allowing the appearance of animal-like life forms.
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Genomicus Member (Idle past 1969 days) Posts: 852 Joined: |
In order to say that the conservation of such-and-such proteins would not be part of an evolutionary prediction, you have to suppose them to have so little use that natural selection would not conserve them. As you say, such a protein needs to be of so little use that "deleting it won't kill the organism, or even significantly reduce its fitness" --- and the significance of its contribution to fitness must in fact be so tiny that selective pressure won't prevent its deletion from becoming fixed in a population. I really don't think you're understanding my argument. It's very simply this: 1. Non-teleological evolution does not predict that the LUCA's genome would encode proteins unnecessary - but functional - to life. 2. Front-loading necessarily predicts this. Confirmation of this prediction therefore, would boost our confidence in FL. And the more instances we find of this, the higher our confidence becomes.
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