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Author Topic:   Deep Homology and Front-loading
bluegenes
Member (Idle past 731 days)
Posts: 3119
From: U.K.
Joined: 01-24-2007


Message 37 of 172 (666053)
06-21-2012 2:15 PM
Reply to: Message 26 by Genomicus
06-20-2012 3:24 PM


I predict "No LUCA"!
Genomicus writes:

There are many problems and challenges facing the FL hypothesis. It's a shaky hypothesis at the moment.

Yes. For one thing, Genomicus, I don't think your predictions make sense on more than one level. Surely the best way to front load a planet "stacking the deck" in favour of multicellular life would be to include eukaryotes along with prokaryotes, and to have as many of each as possible. Also, if there were forms of multicellular life that could be engineered to live and photosynthesise in the early seas, then those would be included. So, a reasonable prediction might seem to be "no LUCA" on such a planet. But there are problems with that also, because we know nothing of the designers, the processes they used, and their technical capabilities.

I think what you're doing with your predictions is a bit like one of our "sideloading" I.D. types suggesting a hypothesis to explain turtles after having observed their existence. "The designer wanted and created turtles" requires and predicts turtles, whereas for evolutionary theory they are compatible, but not a prediction. You can surely see what's wrong with this. A general sideloading hypothesis doesn't actually predict turtles at all. Indeed, I'm not aware of anything specific that the general sideloading idea predicts.

Can the general idea of front loading make any specific predictions when we know nothing about actual process and nothing about the level of technical knowledge the designers had?


This message is a reply to:
 Message 26 by Genomicus, posted 06-20-2012 3:24 PM Genomicus has responded

Replies to this message:
 Message 41 by Genomicus, posted 06-21-2012 4:38 PM bluegenes has responded

  
bluegenes
Member (Idle past 731 days)
Posts: 3119
From: U.K.
Joined: 01-24-2007


Message 45 of 172 (666075)
06-21-2012 7:28 PM
Reply to: Message 41 by Genomicus
06-21-2012 4:38 PM


Re: I predict "No LUCA"!
Genomicus writes:

What do you mean by "no LUCA"? Do you mean that modern life would have evolved from a pool of different species? I have no problem with that, and I don't think the scientific evidence does either.

I'm suggesting that, on any hypothetical planet that was front loaded with the deck stacked in favour of multicellular life, the equivalent of eukaryotes and whatever simple multicellular organisms that could survive should be there.

Geno writes:

Bacteria are by far the best terra-formers, so there's a good reason why they'd be in the original pool. Simple eukaryotes (i.e., "eukaryotes" that had not yet undergone the endosymbiosis event) may have been present as well.

Why take the chance of key endosymbiotic events taking place? Intelligent deck-stacking doesn't need to. If you want such things to arrive, make them. I'm suggesting that, on my hypothetical planet, the array of life that might have existed here one to two billion years ago would have appeared immediately as the first life on that planet (tailored to its circumstances, of course).

Genomicus writes:

Well, we've got a lot of key proteins in eukaryotes that are not found in prokaryotes. So we can actually make a prediction from FLE that isn't ad hoc, namely that we'll find homologs of these proteins in prokaryotes. Note that Darwinian evolution doesn't really predict this (I explain the rationale for this statement in my latest reply to Dr Adequate).

But why does FLE predict this? As we've agreed, the frontloaders could've made their own eukaryotes. Also, as Darwinian processes take place after the frontloading, then why should we expect all important proteins in modern eukaryotes to have homologues in modern prokaryotes even if the FrontLoaders didn't think of making their own eukaryotes?

Genomicus writes:

Well, in the first place I'm taking supernatural, omnipotent designers off the table.

Me too. For an evidence based case, it's best to assume biological aliens. However, as I suggested, this still makes it hard to make predictions when we know nothing of their technical ability and the processes used. Intuitively, it does at least give us a reason why, being multicellular life forms themselves, they might be interested in the kind of project you're suggesting!

Of course, critics of your hypothesis might wonder, if it took 4,000,000,000 yrs for intelligent biologists to emerge from this "stacked-deck" biosphere, how long it took for them to emerge on their "unstacked-deck" planet.

Maybe we can at least get a Sci-fi novel out of this, if nothing else.

Edited by bluegenes, : missing word


This message is a reply to:
 Message 41 by Genomicus, posted 06-21-2012 4:38 PM Genomicus has responded

Replies to this message:
 Message 66 by Genomicus, posted 06-22-2012 10:16 PM bluegenes has responded

  
bluegenes
Member (Idle past 731 days)
Posts: 3119
From: U.K.
Joined: 01-24-2007


(2)
Message 78 of 172 (666310)
06-25-2012 6:16 PM
Reply to: Message 75 by Taq
06-25-2012 3:55 PM


Taq writes:

IOW, FLE is nothing more than the hope of some supernatural guidance in a nominally non-teleologic process.

To say fair, Genomicus seems to deliberately steer clear of implying the supernatural. The hypothesis is that the deck has been stacked on this planet, but not necessarily on the planet of origin of the designers. Unlike other I.D.ists, he never attacks non-telic abiogenesis with spurious probability arguments, and he never claims that the blind watchmaker couldn't have produced the metazoa (including his designers).

That might seem to make Geno's position difficult, but actually any argument for natural intelligent design (a known phenomenon - we do it) is on an infinitely better footing than one for supernatural design.

But you're right about the sharpshooting. I've been attempting what seem to me more reasonable (if conditional) predictions from the general hypothesis. If the hypothesis is that this planet was seeded with the intent of producing metazoa, then I'd suggest that we should see instant biodiversity and no LUCA, because that would be the best way for the designers to minimize risk of complete extinction. More importantly, we should see the maximum possible engineering of shortcuts towards the production of complex metazoa, given the circumstances of the early planet. So, if geochemists were to discover that eukaryotes appear right at the very first point that life appears, that might seem to be a point in favour of directed panspermia.

So I think Geno's problems go beyond Occam's razor and sharpshooting. I don't think that the most obvious predictions of the hypothesis are supported by current evidence at all. Still, Sci-Fi can be fun.


This message is a reply to:
 Message 75 by Taq, posted 06-25-2012 3:55 PM Taq has responded

Replies to this message:
 Message 89 by Taq, posted 06-26-2012 11:32 AM bluegenes has acknowledged this reply

  
bluegenes
Member (Idle past 731 days)
Posts: 3119
From: U.K.
Joined: 01-24-2007


Message 87 of 172 (666341)
06-26-2012 8:24 AM
Reply to: Message 66 by Genomicus
06-22-2012 10:16 PM


Re: I predict "No LUCA"!
Genomicus writes:

Well, eukaryotes aren't as good terra-formers as bacteria, and for front-loading to work on an originally hostile planet, you'd need to terra-form it such that it'll eventually be friendly to complex life forms, like mice and rabbits and trees (and of course, giraffes) etc.

I wasn't suggesting that the frontloaders would load only eukaryotes. The more, the merrier, and the higher the chances of metazoa.

Also, although some eukaryotes can survive extreme environments, prokaryotes are far at surviving extreme environments. Furthermore, since I envision the first life forms arriving on earth via directed panspermia, the eukaryotes would have to survive the space voyage from their home planet to earth.

One more point. Some researchers have in fact proposed that the LUCA was effectively a eukaryote (albeit lacking mitochondria), with prokaryotes "degenerating" from the LUCA.

The last point doesn't really fit very well with the first two, does it? It would also mean that, far from frontloading a prokaryote LUCA with eukaryotes in mind, the frontloaders (FLs) would presumably have had terraforming prokaryotes in mind when designing their eukaryote LUCA. Why not make sure by designing the proks as well? The more, the merrier, and the better the chances.....

And as for FLs leaving out mitochondria in a eukaryote LUCA when they want to frontload metazoa..... come on, Geno, that can't make sense to you!

Genomicus writes:

Ubiquitin is another example. Prior to structural analyses of various prokaryotic proteins, there were no known prokaryotic homologs of ubiquitin. The logic of front-loading predicts otherwise, and indeed, research has uncovered deep homology between ubiquitin and prokaryotic proteins.

Why wouldn't the "logic of frontloading" predict actual ubiquitin in the proks? There's also a problem here that Mr. Jack hinted at in a post above. Ubiquitin being ubiquitous in eukaryotes does not necessarily mean that it's necessary for metazoa, or that the fold is necessary. It could just be a "frozen accident".

The letter "a" is ubiquitous in all languages that use Latin letters, and denotes approximately the same sound(s) in them all. That doesn't mean that the Romans intentionally frontloaded the modern languages with it. More importantly, the "a" sign is arbitrary, and the function could be performed just as well by "$" if the correct protocol were in place. Mr. Jack's "lock and key" analogy might be better to illustrate the more directly physical nature of signalling proteins.

Genomicus writes:

I freely admit that much of the time I'm following my intuition when it comes to the hypothesis of front-loading. My intuition is fallible of course, but that's why I'm not asking any of you to accept front-loading as a valid science at the moment. As I stated earlier, there are many hurdles facing the FL hypothesis.

Yes, I understand that your claims are modest. It's refreshing compared to what we're accustomed to with more conventional I.D. ists, and the tentativity should be appreciated by most of us here.

Geno writes:

Well, there's a lot of time for the nanotechnologists to emerge on a planet that is older then the earth.

They've got to be around 4 billion y.a., which gives them from the moment that the universe could first support life up to 4 bya to evolve. I think that the jury is still out on when the universe could first have supported life. If it was as late as 8 bya, the frontloading biologists arrived just as quickly as us without any "deck stacking".


This message is a reply to:
 Message 66 by Genomicus, posted 06-22-2012 10:16 PM Genomicus has responded

Replies to this message:
 Message 93 by New Cat's Eye, posted 06-26-2012 1:01 PM bluegenes has not yet responded
 Message 109 by Genomicus, posted 06-27-2012 1:10 PM bluegenes has responded

  
bluegenes
Member (Idle past 731 days)
Posts: 3119
From: U.K.
Joined: 01-24-2007


Message 141 of 172 (666596)
06-28-2012 9:13 PM
Reply to: Message 109 by Genomicus
06-27-2012 1:10 PM


Re: I predict "No LUCA"!
Genomicus writes:

Quite right. I personally favor the hypothesis that the LUCA was prokaryotic, and not eukaryotic, although some researchers say that the LUCA was more of a eukaryote precisely because of its complexity and the large number of proteins its genome encoded. This is fully compatible with front-loading.

So, you're agreeing that the frontloaders could have designed a eukaryote. And:

Geno writes:

The universal distribution of ubiquitin among eukaryotes strongly implies that it is necessary for eukaryotic existence, does it not?

I think it implies that it's part of a useful system in them. But that doesn't mean that a complex eukaryote-like cell couldn't have formed in different ways, and couldn't have used different proteins for a similar function.

True, it could be a "frozen accident." But the front-loaders aren't going to gamble their chances on accidents. It would be far better design logic just to put that protein fold into the first cells.

I like this:

But the front-loaders aren't going to gamble their chances on accidents.

It's exactly what you're suggesting they did do. Let's look at your scenario. The FLs design a prokaryote with the metazoa in mind. They say to themselves: "at some point in the future, two descendents of our LUCA will combine in a way that will form a more complex cell which potentially could evolve into metazoa. These two particular descendents, maybe hundreds of millions of years down the line, maybe more than a billion, will contain all the proteins that we've put into the LUCA for their use."

If that's not gambling, what is?

I'd suggest that the frontloaders wouldn't be able to predict anything as specific as our eukaryotes. They might well know from their own life system that endosymbiotic events that produce useful functions could happen if their prokaryotes bubble away for long enough. But what they can't know is, if they do get lucky and get a more complex cell, specifically how it would form.

If they were trying to maximise the probability of metazoa, they would know that it would require something like mitochondria to power it. Surely that's what we'd expect to see frontloaded, isn't it? Any thing else seems like heavy gambling.


This message is a reply to:
 Message 109 by Genomicus, posted 06-27-2012 1:10 PM Genomicus has responded

Replies to this message:
 Message 162 by Genomicus, posted 07-03-2012 1:56 PM bluegenes has not yet responded

  
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