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Author Topic:   Deep Homology and Front-loading
Genomicus
Member (Idle past 16 days)
Posts: 852
Joined: 02-15-2012


Message 1 of 4 (665896)
06-19-2012 1:47 PM


In a previous thread, I have discussed the concept of front-loaded evolution as a testable teleological hypothesis. This caused a good bit of disagreement, as many of you are quite adamant that FLE doesn’t make any exclusive predictions. Contrary to this, I think FLE does, in fact, make a prediction that the current evolutionary paradigm does not.
Before beginning, let me explain exactly what the front-loading hypothesis is, as some of you have misconceptions about it.
Front-loading is all about designing future states through the present. Here’s how Mike Gene, the guy who first conceived of the idea of front-loading, defines it:
“Front-loading is the investment of a significant amount of information at the initial stage of evolution (the first life forms) whereby this information shapes and constrains subsequent evolution through its dissipation. This is not to say that every aspect of evolution is pre-programmed and determined. It merely means that life was built to evolve with tendencies as a consequence of carefully chosen initial states in combination with the way evolution works.
Front-loading does not allow for a prediction of specific outcomes, at a specific time and place, but does allow that specified outcomes can be made much more likely...”
(The Design Matrix, p. 147).
According to the front-loading hypothesis, one of the objectives of front-loading was the rise of eukaryotes and multicellular life forms. And if multicellular life forms were front-loaded, this can serve as a springboard from which we can make several predictions.
So, how would a designer(s) front-load multicellular life forms through unicellular life forms? You’d simply have to load the first genomes with proteins that would later be utilized by the multicellular life forms. For example, histones seem to be universally required by eukaryotes. Thus, loading the first genomes with histones (or their analogs) would make the appearance of eukaryotes more likely (and front-loading is all about “stacking the deck” in favor of the appearance of multicellular life forms). Without histones in the first genomes, the evolution of eukaryotes is left solely to the blind watchmaker’s tinkering. And without specific information to guide and constrain the path of evolution, such that it is “nudged” in the direction of eukaryotes, there’s no guarantee that histones will evolve. Consequently, the likelihood that eukaryotes would evolve drops considerably. A front-loading designer can make the evolution of eukaryotes much more likely by packing the first genomes with eukaryotic proteins (or their analogs), such that evolution will build around these proteins, eventually producing the objective.
From here we can make a prediction: key eukaryotic proteins will share deep homology with functional but unnecessary prokaryotic proteins.
The homologous protein in prokaryotes will be functional because if the designer loads up the genome with proteins that will only find function millions of years later, these proteins will decay into oblivion, eliminating the whole purpose of front-loading. But if these homologous proteins are unnecessary in that they are not required for the basic prokaryotic cell, then we have a successful prediction of front-loading. Non-teleological evolution does not make this prediction.
This is because, under non-telic evolution, the LUCA’s genome could easily have been a minimal genome that only encodes the proteins absolutely necessary for the existence of a prokaryote cell. Non-teleological evolution does not require this; but nor does it require that the LUCA’s genome encodes more than is necessary. We can summarize this state of affairs thusly: non-teleological evolution makes no predictions regarding the gene/protein content of the LUCA, other than the obvious fact that it would have to encode the proteins necessary for its existence. On the other hand, front-loading specifically predicts that the LUCA will contain more proteins than is necessary for prokaryotic existence. If the front-loader only designed the LUCA such that it encoded the bare minimum required for life (about 250 genes or so), there’s no “stacking of the deck” in favor of the evolution of multicellularity. In short, front-loading, by its very definition, requires the loading of the LUCA’s genome with unnecessary (but functional!) proteins – proteins that are required for the rise of eukaryotes and multicellularity.
I will now briefly address the objections that I’ve come across so far:
1. If evolution can explain something happening, it also predicts that it can happen (source: Dr Adequate). The modern evolutionary theory might be able to explain some biological feature, while an ID hypothesis would predict that biological feature. If the prediction is confirmed, this is evidence for that ID hypothesis, regardless of whether non-telic evolution can explain it or not. Science is built upon a track record of successful predictions, not on whether some alternative model can explain the feature under consideration. Consider the following example. Evolution predicts that if the bacterial flagellum evolved, a number of its components will share similarity with proteins that are more ancient than the bacterial flagellum. Can the hypothesis that the flagellum was engineered explain this? Yes. Engineers very often re-use parts in different systems. But the ID hypothesis does not predict that the flagellar components will share similarity with more ancient proteins. This is because engineers can also design from scratch. So, while ID can explain this, it does not predict it. Which means that, when it comes to similarity, evolution is the superior explanation.

2. 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 (source: PaulK). In my humble opinion, evolutionary theory – that is, the current biological paradigm – doesn’t make a prediction either way regarding the gene content of the LUCA. Under evolutionary theory, LUCA would not be expected to have more genes than necessary any more than it would be expected to have only the bare minimum. This is because, under non-teleological evolution, the LUCA could have been simply a self-replicating molecule, encoding only a few genes. This population of self-replicating molecules would then diverge, producing different domains of life. But under front-loading, the LUCA would have to have more genes than necessary because there’s no reason to suppose that a minimum gene set could specifically evolve into multicellular life forms, given that there are many directions in which this minimum gene set could evolve. Only a few of the paths consist of multicellular life forms of the type we see today, while the vast majority of possible evolutionary trajectories does not consist of the multicellular life forms we see today. So, to front-load these life forms, you’d need to load the LUCA’s genome with genes that would make the appearance of these life forms more probable.

One more point. I’d like to correct something I stated earlier. Previously, I said something to the effect that these functional but unnecessary proteins in prokaryotes would be so unnecessary that deleting them wouldn’t significantly affect fitness. This is not correct. Deleting them might kill the organism under consideration. Nevertheless, if a given gene is required for one prokaryote, this does not mean that it is required by all prokaryote life forms. So, by “unnecessary but functional” I mean a gene that is not required by the basic prokaryote cell plan but does carry out a functional role in the LUCA.


Tangle
Member
Posts: 6667
From: UK
Joined: 10-07-2011
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Message 2 of 4 (665901)
06-19-2012 2:25 PM


So, the Old Testament is wrong then?

(This sounds off-topic, but it goes to motive, m'lud.)


Life, don't talk to me about life - Marvin the Paranoid Android

Wounded King
Member (Idle past 2169 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 3 of 4 (665903)
06-19-2012 2:42 PM


This looks like it should be a 'Proposed New Topic', and a potentially interesting one, did you put it in the Board Admin. Suggestions and Questions section by mistake?

TTFN,

WK


Replies to this message:
 Message 4 by Genomicus, posted 06-19-2012 2:44 PM Wounded King has not yet responded

  
Genomicus
Member (Idle past 16 days)
Posts: 852
Joined: 02-15-2012


Message 4 of 4 (665904)
06-19-2012 2:44 PM
Reply to: Message 3 by Wounded King
06-19-2012 2:42 PM


This looks like it should be a 'Proposed New Topic', and a potentially interesting one, did you put it in the Board Admin. Suggestions and Questions section by mistake?

Yes. Apologies. Will move it over to the "Proposed New Topics."


This message is a reply to:
 Message 3 by Wounded King, posted 06-19-2012 2:42 PM Wounded King has not yet responded

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