This month's "Edge of Knowledge" peers back in time to the beginnings of life on Earth.
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Paul Sutter explores the origins of life, and DNA versus RNA
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Very nice. It's still hard to imagine how a soup (dilute or not) overcame entropy to make us what we are today--but it's a fascinating topic!
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Multiply wrong.
1) In the transcription of genes, DNA provides the information for an equivalent piece of RNA, but the enzymes that perform that transcription are made of protein and RNA.
2) DNA precursors are made from RNA precursors. This is the work of ribonucleotide reductase.
Also, when Dr. J. Timmer explains that DNA differs from RNA by only a single atom, it might be helpful to show some more detailed diagrams. Depicting a nucleotide base as a single sphere does not convey that information.
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Won't have time to watch this until late tonight. But just want to say this is one of the big questions on my bucket list that I hope will get answered before I'm gone.
Other questions on my bucket list include (1) what is consciousness, (2) what is time (no, not 9:00 am), and (3) what is the ultimate/underlying nature/fabric of reality. But if I live to be 1000 years old, I doubt we'll have solved #3, just peeled more layers off the onion.
Other questions on my bucket list include (1) what is consciousness, (2) what is time (no, not 9:00 am), and (3) what is the ultimate/underlying nature/fabric of reality. But if I live to be 1000 years old, I doubt we'll have solved #3, just peeled more layers off the onion.
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Genetics First vs. Metabolism First - this is probably a false dichotomy. Sure, those genetics would need to occur in a suitable chemical background; but a collection of chemical reactions providing precursors is not what we consider "life." It does not store and replicate information as specified in the definition of life presented, nor in most definitions of "life."
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That first paragraph in the transcript is pretty hard to read, so I split it into paragraphs below. The rest of the transcript is OK.
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We're putting energy into the system, so there's not a problem of entropy.
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I still subscribe to the theory that early Earth was an emergency pit stop for a family of Vogons who made the mistake of stopping at the interstellar equivalent of a Taco Bell.
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re consciousness. Take a look at 'a journey into the animal mind' by Ross Anderson in the Atlantic circa 2020. I read it in a compendium 'the best science and nature writing 2020 Michio Kaku editor.
nic out
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Dated March 2019. I am still reading, but I like the focus on animals. Any discussion centered on "human consciousness" that ignores the rest of the animal world is going to be deeply flawed.
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Just in. “Edge of Life” banned in Florida for spreading heresy.
We all know the world is not billions of years old, it’s in the Bible. “The Creation Museum, “holds that God made the universe in six 24-hour days about 6,000 years ago.”
Darwin, bah humbug.
Originalists (including the Supreme Court) go biblical, that’s America in the 21st century.
We all know the world is not billions of years old, it’s in the Bible. “The Creation Museum, “holds that God made the universe in six 24-hour days about 6,000 years ago.”
Darwin, bah humbug.
Originalists (including the Supreme Court) go biblical, that’s America in the 21st century.
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Though it probably won't help the "God did it" trolls,the Talk.Origins FAQ has sections on the most common "rebuttals" to evolution and abiogenesis (e.g., "some parts of a person are so complex they had to be designed").
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I can understand school libraries (won't someone please think of the children), and the children's section of public libraries, but why are some books banned from the adult section of public libraries? Isn't there free speech or freedom of the press or something like that?
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My reaction was also along those lines
If you need both Genetics and Metabolism, then it is likely the easier one existed off and on over a long period of time before it managed to co-exist with the harder one, resulting in the necessary (but until that point, absent) stability. They both could have developed, and been lost, independent of each other numerous times before things aligned perfectly to result in life.
We often think about the origin of life as a single event, but it could very well have occurred more than once for shorter periods of time, before it was extinguished. Only to re-occur later somewhere else. Eventually it persisted in an unbroken line through to today, but that doesn't necessarily have to be the first time, only the last time.
If life is an emergent phenomenon (which it kind of has to be based on current theories), then a single emergence seems implausible to me.
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Hi,
I want to add one very important point : DNA replication is not enough, to evolve (and find another possible viable "solution") you need also random errors.
Replication without errors cannot lead to continous evolution...
I want to add one very important point : DNA replication is not enough, to evolve (and find another possible viable "solution") you need also random errors.
Replication without errors cannot lead to continous evolution...
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It doesn't even have to be the last time. If a new origin of life happened yesterday, that life would find it very hard to compete with extant life that have already gobbled up all of the available niche space.
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Very true. There were probably dozens of new origins just in the primeval soup of my university days fridge that we never knew was there that arose and were consumed by the hardier lifeforms there in the harsh, corrosive environment of expired milk, half-drunk beer and old pizza slices.
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Peanut Butter disproves scientific theories of origin of life (claims creationist)
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The thought of having to listen to such a prima facia moronic argument gives me nightmares anyway.
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Speakertoanimals
Ars Tribunus Militum
When I replaced my gutters, I had to prima facia the board before I painted it.
The thought of having to listen to such a prima facia moronic argument gives me nightmares anyway.
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Cap'nAwesome
Ars Centurion
If anyone wants to read more on this and other topics (yet keep it understandable to the layman, such as myself) I thoroughly enjoyed the book A Brief History of Earth: Four Billion Years in Eight Chapters
by Andrew H. Knoll.
by Andrew H. Knoll.
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Because of how complex DNA is I have a hard time believing life originated here on Earth randomly.
I have an easier time believing it started somewhere else and somehow found its way here.
I have an easier time believing it started somewhere else and somehow found its way here.
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You are correct. More generally, one of the clinching pieces of evidence for "RNA world", is that RNA can perform catalysis (the polymerase is one such marvel).
RNA is inherently unstable , good for evolution.
RNA viruses that are airborne (e.g. COVID), must be wrapped in a lipid and reach a target very soon.
There are other forms of DNA and synthetic amino acids (see George Church), we might yet find more.
If the experiment was run again, the chances of life are high, homo sapiens not so much...
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That leaves the question of how it started elsewhere; or is it turtles all the way down?
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Can we talk more about how all Earth life is genetically descendant from the primitive life found in deep-ocean geothermal vents?
Two possibilities for that:
1. That's where life started on Earth.
2. That's the only place life survived a literal scorched-Earth cataclysm.
Two possibilities for that:
1. That's where life started on Earth.
2. That's the only place life survived a literal scorched-Earth cataclysm.
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Very true. Just don't like the idea that Earth is somehow special in a universe full of planets and suns.
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I think the greater likelihood is the that life arose independently here.
Given interstellar distances, an object would have to be traveling at relativistic speeds ... then for anything organically complex (i.e. more than just molecules) to survive that impact with Earth? Seems unlikely.
If the theory is that extra-terrestrial life seeded the Earth less than 1 billion years after the Earth formed, either that's a huge coincidence or life should be fairly common in the cosmos ... I guess we will find out when we are able to take more samples from places like the asteroid belt and Oort cloud.
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Well, out of 9 planets in the solar system (was effectively indoctrinated as a child, won't give up on Pluto) ... only Earth is able to sustain higher forms of life like humans. So that's pretty special already.
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Why do I suspect that there is a Rule 34 violation in the offing?
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It sounds like we are on the same path.
For many molecular biologists, the cherry on top for the RNA World Theory (yes, I am giving it a promotion) was the 3D structure of the ribosome around the turn of the century. Ribosomes consist of dozens of distinct pieces of protein and RNA, but the structure revealed that the catalytic core of the ribosome is a ribozyme (RNA enzyme).
Since then, the case for the RNA World has grown even stronger with results that indicate RNA precursors could have come about through alternate pathways (e.g. Powner, Gerland & Sutherland 2009).
As for how DNA developed from RNA, some virologists compare it with other nucleotide modifications such as methylation. Possibly it came out of a virus-host arms race.
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Regarding 3, I think the question itself is pretty meaningless. What do you mean by "ultimate underlying nature"? I don't even know how to interpret this phrase, let alone try to answer it. Do you actually understand what you are asking?
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What do you mean by this?
Is it the complexity of individual nucleotides that worries you, or the complexity of long polymers?
If the latter, I would point out that the complexity of genomes has increased over time.
The fact that you say "DNA" rather than "RNA" makes me discount your concerns. It appears that RNA was here first, and that DNA came about as a modification of RNA.
The ability of nucleotide monomers to polymerize, and depolymerize is simple chemistry. Cycling through these steps can be driven by temperature(as in PCR, although that is catalytically assisted of course) or by concentration(which could in turn be driven by freeze-thaw cycles).
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gaaaa.... with a wrong (left-handed) twisting DNA molecule depicted right behind him! (it burns! it burns! the eyes of an old structural biochemist) flop the image quick!
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Team Tardigrade
Ars Centurion
Hello creationists! When you discount evolution based on something being so complex it could never evolve by itself (like DNA, or the human eye), you probably mean that something very complex didn't just randomly show up one day - and you're absolutely right!
Things like DNA, the eye, or any other product of a complex emergent system doesn't just show up fully formed. They start with very small and simple things like small molecules or a group a shitty photosensitive cells on the surface of tissue. Over time these small and simply things start to slowly get bigger and more complication. In fact, this is what evolve means! To change over time.
No, it's cool with me if you still don't want evolution, but I'm going to have to ask you to give up all antibiotics because (on noes!) we keep making new ones since the bacteria have evolved over time and no longer die when exposed to old simple antibiotics like penicillin. Oh. And that food you're about to eat? Yeah, sorry, it too has changed over time. No more eating for you!
Things like DNA, the eye, or any other product of a complex emergent system doesn't just show up fully formed. They start with very small and simple things like small molecules or a group a shitty photosensitive cells on the surface of tissue. Over time these small and simply things start to slowly get bigger and more complication. In fact, this is what evolve means! To change over time.
No, it's cool with me if you still don't want evolution, but I'm going to have to ask you to give up all antibiotics because (on noes!) we keep making new ones since the bacteria have evolved over time and no longer die when exposed to old simple antibiotics like penicillin. Oh. And that food you're about to eat? Yeah, sorry, it too has changed over time. No more eating for you!
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In "modern" life, you are certainly correct. But people have identified ribozymes (RNAs that function as enzymes) that are capable of performing reverse transcription (copy RNA into DNA) (https://elifesciences.org/articles/31153), ribozymes that can self diversify (https://pubs.rsc.org/en/content/article ... d1cc02290c), and many people believe that because the active portion of the ribosome is the RNA, that protein synthesis is originally based on a ribozyme type element.
So the RNA world is plausible, at least, and it may be that now RNA requires protein for certain activities, but did not require protein originally, just evolution selected for mixed RNA/protein complexes.
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