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#176 llanitedave

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Posted 02 May 2013 - 10:39 PM

if we have found portions of the "building blocks of life" in meteors, wouldn't this suggest that the Universe is well populated?


Not really, because "well" is a subjective adjective, and we don't know how well well is.

It does suggest, though, that life elsewhere is not impossible. It has no implications about how abundant or rare that life might be.

#177 llanitedave

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Posted 02 May 2013 - 10:48 PM

This thread has run off the rails and is in danger of completely derailing
and running into an oncoming freight train.

Since the subject is the "origin of life" then the problem can be framed
as how do biological systems arise from prebiotic conditions in terms of
chemistry & molecular biology?

It would seem the minimum necessary requirement is a molecule which can
encode information which is both self-replicating and can function as
as a catalyst, like enzymes in modern cells do.

A likely candidate is RNA, which has led to the RNA World hypothesis, a term
coined by Walter Gilbert, a former theoretical physicist turned Nobel
Prize winning molecular biologist.

RNA can carry genetic information in the sequence of bases (purines &
pyrimidines), can replicate that information, and in configurations
known as Ribozymes can function as an "honorary" enzyme.

In this scenario, RNA predated both DNA and proteins (all enzymes are proteins,
but not all proteins are enzymes). The main problem is how RNA or a similiar
molecule arose from pre-biotic conditions. The problem appears difficult, but
not impossible.


The other big question it leads to is whether RNA, and by extension DNA, is the default pathway for metabolically active replicators. Or alternatively, how many plausible inheritance molecules could exist?

My assumption has always been that DNA for life on earth, rather than some other molecule, is a historical happenstance, an evolutionary die that was cast in the distant past. But if the RNA world is a predictable result for conditions amenable to life, and necessary for it to move past protocells, then my assumption would be wrong.

#178 StarWars

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Posted 02 May 2013 - 11:18 PM



The human being is a complex bag of water and most likely did not evolve from a turnip or platypus... (sorry Darwin) :(

#179 llanitedave

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Posted 03 May 2013 - 02:44 AM

Sorry Darwin?

Do you know of anywhere that Darwin, or any other scientist, for that matter, claims humans evolved from a turnip or a platypus?

#180 Qwickdraw

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Posted 03 May 2013 - 05:28 AM

I think it would suggest that the universe is well-supplied with building blocks. It doesn't answer the question of how often they get put together properly to form life.

Jarad


"get put together" would suggest intervention which is entirely plausable IMO :grin:

#181 Jarad

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Posted 03 May 2013 - 06:03 AM

I am perfectly happy to entertain that hypothesis as soon as you find some observational evidence for it that can't be explained by any current theory.

Jarad

#182 llanitedave

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Posted 03 May 2013 - 09:29 AM

If by "intervention" you mean the laws of chemistry, then sure. After all, water molecules have to get "put together properly" to form ice crystals, carbon and hydrogen have to be "put together properly" to form ethane...

The complexity of the system has nothing to do with the physical means of assembly.

#183 TVG

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Posted 03 May 2013 - 09:34 AM

I believe entropy would play a significant role with this, would it not?

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#184 ColoHank

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Posted 03 May 2013 - 09:36 AM

The human being is a complex bag of water and most likely did not evolve from a turnip or platypus... (sorry Darwin)



More than likely, humans and turnips and platypuses all evolved from the same primordial ooze, perhaps something that formed around a geothermal vent in some ancient sea. The different journeys have been long and difficult, no doubt with innumerable trials and failures along the way, but here we all are: distant cousins in the form of humans, turnips, and platypuses. I know that's hard to imagine, particularly for anyone who's unable (or even worse, unwilling) to acknowledge that we know more now about all manner of things than we did way back when, but what other possible explanation could there be for the existence of turnips? Nobody in His right mind would have created one.

#185 moynihan

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Posted 03 May 2013 - 10:14 AM

I am not sharing this quote because it is or is not scientifically valid, i just like.

"Just as the constant increase of entropy is the basic law of the universe, so it is the basic law of life to be ever more highly structured and to struggle against entropy."
Václav Havel

In one of his first speeches of his presidency of the new Chech republic, he said, "sometimes i see life as the universe's trying to do an end run on the 2nd law of thermodynamics."
What a politician, and what an audience it was that cheered the line :grin:

#186 llanitedave

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Posted 03 May 2013 - 11:17 AM

But in the end, the result is the same:

"You can't win, you can't break even, and you can't quit"

#187 Joad

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Posted 03 May 2013 - 12:04 PM

But you can be perfectly comfortable, even happy, with refusing to play DNA's game and opting to let at least your own personal DNA end with you.

I will admit that the real mystery to me is how some of us are able to do this, but we are.

#188 StarWars

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Posted 04 May 2013 - 01:15 AM

The human being is a complex bag of water and most likely did not evolve from a turnip or platypus... (sorry Darwin)



More than likely, humans and turnips and platypuses all evolved from the same primordial ooze, perhaps something that formed around a geothermal vent in some ancient sea. The different journeys have been long and difficult, no doubt with innumerable trials and failures along the way, but here we all are: distant cousins in the form of humans, turnips, and platypuses. I know that's hard to imagine, particularly for anyone who's unable (or even worse, unwilling) to acknowledge that we know more now about all manner of things than we did way back when, but what other possible explanation could there be for the existence of turnips? Nobody in His right mind would have created one.



Don't forgets about the Mosasaurus..... :scared:


http://www.youtube.c...h?v=pSj7-Dx4sWs

http://www.youtube.c...h?v=_xDXrYw3ArE

#189 llanitedave

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Posted 04 May 2013 - 09:19 AM

And beetles. An inordinate fondness for beetles.

#190 moynihan

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Posted 04 May 2013 - 11:01 AM

And beetles. An inordinate fondness for beetles.


:jump:

#191 llanitedave

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Posted 04 May 2013 - 10:12 PM

But you can be perfectly comfortable, even happy, with refusing to play DNA's game and opting to let at least your own personal DNA end with you.

I will admit that the real mystery to me is how some of us are able to do this, but we are.


A number of years ago I started playing with genetic algorithms. I produced a couple of toy programs for my own amusement and ran them repeatedly.

My biggest surprise was that most lineages became extinct, even if they began with equal fitness to other lineages. ("Lineage" is actually a pretty fuzzy concept in a sexually reproducing population, since they also get remixed very thoroughly, but it also can include specific genetic sequences that are not subject to active and continuous selection). A reproducing population can continue indefinitely even if only a small subset of its genetic material is conserved.

If you think about Mitochondrial Eve and Y Chromosome Adam, who lived roughly 200,000 and 500,000 years ago, respectively, it becomes pretty clear. ME was not the first woman, nor was she the only woman of her generation. There were many thousand human women living at the same time that she was. Each had a unique mitochondrial lineage. Every single one of those lineages has gone extinct since then except hers (and of course that of all her female ancestors up to the time of the first mitochondria). Yet at the same time, the human population has grown enormously, even though most of its genetic lineages have failed.

And you can't say that either Mitochondrial Eve's mitochondria or Y-chromosome Adam's Y-chromosome genes were any more "fit" than those of their contemporaries. In a contest of equals, there can still be only one winner, if that's how the game is set up.

The lesson, I think, is that even if continuing your DNA into the future is your highest priority, chances are it won't happen anyway. So if you've decided not to worry about your DNA's future, you haven't really lost anything. Nature has ensured that there will be plenty other DNA-donors jockeying for position.

#192 StarWars

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Posted 05 May 2013 - 01:29 AM

The human being is a complex bag of water and most likely did not evolve from a turnip or platypus... (sorry Darwin)



More than likely, humans and turnips and platypuses all evolved from the same primordial ooze, perhaps something that formed around a geothermal vent in some ancient sea. The different journeys have been long and difficult, no doubt with innumerable trials and failures along the way, but here we all are: distant cousins in the form of humans, turnips, and platypuses. I know that's hard to imagine, particularly for anyone who's unable (or even worse, unwilling) to acknowledge that we know more now about all manner of things than we did way back when, but what other possible explanation could there be for the existence of turnips? Nobody in His right mind would have created one.



With all the doctors of science and super computers I would think they could definitively reverse engineer the human DNA back to the turnip and platypus... :o


If it doesn't make sense then it's not true....... Judge Judy

#193 Mister T

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Posted 05 May 2013 - 06:04 AM

or the turnip truck

#194 Otto Piechowski

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Posted 05 May 2013 - 06:17 AM

Dave,

I am interested in knowing if you attempted/did the following or could extrapolate a conclusion based on the information you have from the studies you did:

Let us imagine that "Eve" was not created or died out. Does another female lineage replace "Eve's" and populates the earth?

Otto

#195 moynihan

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Posted 05 May 2013 - 07:36 AM

But you can be perfectly comfortable, even haThe lesson, I think, is that even if continuing your DNA into the future is your highest priority, chances are it won't happen anyway. So if you've decided not to worry about your DNA's future, you haven't really lost anything. Nature has ensured that there will be plenty other DNA-donors jockeying for position.


One time when Darwin was asked what he saw as the key distinction between us and the rest of "creation", he replied that he could get up in the morning and decide not to reproduce. ;)

#196 llanitedave

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Posted 05 May 2013 - 10:00 AM

Dave,

I am interested in knowing if you attempted/did the following or could extrapolate a conclusion based on the information you have from the studies you did:

Let us imagine that "Eve" was not created or died out. Does another female lineage replace "Eve's" and populates the earth?

Otto


Here's a difficult concept, for me, at least. "Mitochondrial Eve" was a real woman. But we only know of her indirectly, through the Mitochondrial DNA that has descended from her. And her identity is not as some individual, but more like a job description. It's a functional position, like "Queen Mother", or "Secretary of Ancestry". By definition, this Eve had to have had at least two daughters, (two, at least, who survived to reproduce) and at least one of those daughters had a mutation in in her mDNA that made it distinct from that of her sisters'. It need not have been a large mutation, or one of any functional consequence. It only need be traceable.

Through the generations, this bifurcation in DNA sequences continued, occasionally producing other bifurcations, until there is now a scattering of six major subgroupings, or haplogroups. Interestingly, Non-Africans all tend to host a single haplogroup, while Africans distribute the other 5.

Let's assume that a global disaster occurred, and all Europeans and Asians were to suffer extinction, wih only a few African groups surviving. Would the current Mitochondrial Eve still be valid?

No. The person who we now call Mitochndrial Eve would still have existed, of course, but the title would pass to one of her descendants, the one who gave birth to the most distantly surviving bifurcation.

There's another possibly difficult point: Mitochondrial Eve is NOT our only female ancestor. The only DNA she necessarily contributed to all of us is that of our mitochondria. Mitochondria are only passed down from mother to daughter. We had many other female ancestors, but all of those necessarily included at least one male in the ancestral line. It's highly possible that she contributed NO nuclear DNA, some of which could have been supplied by any of her contemporaries. Because nuclear DNA experiences recombination and mixing, and can come from either males or females, there is no way to trace it into the distant past (with the exception of some marker sequences, perhaps). Her descendants did not populate the Earth, because the Earth (or at least Africa -- and Europe and Asia if one counts Neandertals and Denisovans) was already populated. She merely supplied a single easily traceable genetic marker. Plenty of others could have supplied the rest.

So what if Mitochondrial Eve had never existed? Well, if that woman happened to be named Ayla and lived in the Sudan 200,000 years ago, and if someone went back in time and accidentally landed their time machine on top of her -- the human race would not suddenly have never existed. There were plenty of other women who could have been Mitochondrial Eve had their mDNA had the right opportunities. Maybe a woman who lived prior to Ayla, possibly her grandmother, might have been the title-holder. Maybe her cousin. Maybe a distant relative in Ethiopia. As I mentioned before, inheritance in single lineages is not necessarily a competition based on fitness. It can very well be a contest of equals. And if one competitor is eliminated, there are many others standing by.

#197 Otto Piechowski

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Posted 05 May 2013 - 12:10 PM

I understand. Thank you. Otto

#198 StarWars

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Posted 05 May 2013 - 04:04 PM

or the turnip truck



Darwin delivered turnips in a truck... :lol: :roflmao:

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#199 minos

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Posted 16 May 2013 - 10:27 AM

If by "intervention" you mean the laws of chemistry, then sure. After all, water molecules have to get "put together properly" to form ice crystals, carbon and hydrogen have to be "put together properly" to form ethane...

The complexity of the system has nothing to do with the physical means of assembly.


Accumulation of reactions leads to complexity!Because of the second law of thermodynamics, the creation of complexity cannot be the driving force of the events, but it rather emerges as the natural result of the accumulation of many simple spontaneously occuring events

#200 llanitedave

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Posted 16 May 2013 - 06:13 PM

Again, entropy in action. Matter condenses as energy dissipates, and because matter has inherent structure, it condenses into specific structures rather than featureless lumps.






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