7 ms·

Cosmic rays may explain life’s bias for right-handed DNA (2020)

88 points by deesep 4y ago

deleted 4y ago
[deleted]
platz 4y ago
I finally know what the definition of “evil” life is. Thank you.
- xwdv 4y ago
  When you look at the DNA of evil beings, such as the kinds you might pull through a portal to hell, you would find their DNA spirals to the left instead of the right. It implies hell is bathed in high energy rays with opposite polarization from the cosmic rays in our own universe.
  - BuyMyBitcoins 4y ago
    If true, Hell is indeed a sinister place.
  - nextaccountic 4y ago
    This also explains why left-handed people are identified with the devil. The whole universe is biased against being left-handed https://en.wikipedia.org/wiki/Bias_against_left-handed_people https://en.wikipedia.org/wiki/Bias_against_left-handed_peopl...
  - h2odragon 4y ago
    It doesn't explain why the people on the other side of the portal favor goatee styled facial hair, tho. That is a deeper mystery.
  - idlewords 4y ago
    The problem with this explanation is that the high temperature of hell would tend to racemize enantiomeric mixtures, and this process would easily dominate the very low cosmic ray effect.
- fractallyte 4y ago
  The origin of the word sinister... https://www.merriam-webster.com/words-at-play/sinister-left-dexter-right-history https://www.merriam-webster.com/words-at-play/sinister-left-...
bmitc 4y ago
The article never explains why right-handed polarization knocks electrons off right-handed helixes more often than left-handed ones. What's the mechanism there?
- photochemsyn 4y ago
  The linked paper has some clues: > "Muller (1927) that showed that the mutation rate is proportional to the radiation dose, much of it attributable to ionization by cosmic rays. The muon component dominates the flux of particles on the ground at energies above 100 MeV, contributing 85% of the radiation dose from cosmic rays (Atri & Melott 2011). Muons have an energy sufficient to penetrate considerable depths, and they are, on average, spin-polarized. Ionization by spin-polarized radiation could be enantioselective (Zel'dovich et al. 1977). Therefore, we argue that the mutation rate of live and evil organisms would be different. As there could be billions or even trillions of generation of the earliest and simplest life forms, a small difference in the mutation rate could easily sustain one of the two early, chiral choices." https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6 https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6 The actual models and calculations they employ to get an estimate of bias are really complicated, but if I read correctly, it's only a diffence of +/- 10^-7 relative to 50:50 equality: https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6#apjlab8dc6app2 https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6#... They suggest this is somehow amplified over time, but it's equally likely life just settled on one or the other handed version randomly.
  - platz 4y ago
    you appear to have failed to understand the question that the questioner was asking.
    - photochemsyn 4y ago
      There are three models in the second link describing the possible mechanisms, none of them seem all that condensable. E.g. this seems to be at the center of one of their approaches: > "If we only consider second-order perturbations, involving two atomic sites in addition to O, the interaction cannot be geometrically chiral. So, if the fount is completely isotropic, we need to consider third-order perturbations, involving three distinct atomic sites, in addition to O, to have the possibility of a chiral coupling. Furthermore, it is apparent that the strength of the perturbations associated with each site is proportional to the scalar charges Q, and a third-order perturbation to the mutation rate will be simply proportional to the product of these charges, which is unchanged on inversion. It is only their relative locations that matter." > "There are several types of third-order perturbation. For example, we can use the first-order displacement due to the first charge to evaluate the electric field due to the second charge along the perturbed trajectory and compute a second-order velocity perturbation to calculate the third-order magnetic displacement at O. Alternatively, we can take the second-order displacement at O and combine this with the electric field due to a third charge to calculate a third-order change in the kinetic energy of the cosmic ray at O. We must then sum over all permutations of charge..." See also Fig B3: > "Figure B3. Example of electric chirality (barber pole model). The electric charge distribution of two biopolymers of opposite chirality projected onto a cylinder is shown, together with the unperturbed vs. perturbed trajectory of a magnetically polarized cosmic ray interacting with the molecule."
phyzome 4y ago
You could just as well say that the cosmic ray pions are more likely to destroy right-handed DNA, which would have the opposite effect. And I don't think essential mutations were particularly hard to come by in the primordial soup. UV light works fine, as do many, many chemicals. Or just more-primitive copying machinery. I don't think this weighs very heavily against the random symmetry-breaking hypothesis.
- SideburnsOfDoom 4y ago
  > You could just as well say that the cosmic ray pions are more likely to destroy right-handed DNA, which would have the opposite effect. You could, and it's going to be one effect or the other that is stronger - One of the chiralities will have an advantage due to this effect, relative to the other. And now we know which one.
  - yyyk 4y ago
    >You could, and it's going to be one effect or the other that is stronger... And now we know which one. If the result would have been the other way around, we could have had here on NH the same story with the same argument with about the same conclusion. That's not very helpful. Note also the null hypothesis (none of these 'effects' matter, and choice is rather random) has the same non-explanatory potential as the story does.
- thomastjeffery 4y ago
  We already know the conclusion of this story: right-handed DNA is what exists today. The effort here is not to create a story blindly from known fundamentals into wherever that story might lead. The effort is to fill the gap in story from known fundamentals to a known conclusion. We don't know if other circumstances could have lead to another conclusion, and that would indeed be an interesting question to answer. But we do know that the conclusion we are living in somehow favored right-handed DNA. If this backstory leads to two potential conclusions - either left-handed or right-handed DNA, and not both - and we are already experiencing one of those conclusions (right-handed DNA), then it is OK for that backstory to be ambiguous. We don't need to prove the impossibility of the left-handed result. We only need to illustrate the impossibility (or unlikelihood) of both conclusions existing together at the end of the story.
tough 4y ago
As a leftie I wonder what cosmic rays did to me
- Lapsa 4y ago
  yeah, article initially reads somewhat confusing
Aardwolf 4y ago
The only thing that actually showed something asymmetric was, afaik, the image showing cosmic rays coming towards you with a certain magnetic polarization of muons. So if cosmic rays themselves would have had the other polarity (coming with N towards you and S away from you), then instead left handed would have been more advantageous? But, then, what's the reason why we don't have any cosmic rays with inverted polarization? Also, I think that even if the cosmic rays were not an issue and there was no advantage between left and right, only one of them would eventually survive: if there were both lifeforms with the left and the right orientation, they'd be competing for the same resources (while only being able to mutate/copy/evolve within their own type). Eventually one branch is bound to die out while the other remains, even if due to sheer luck rather than large advantage, and from then on the opposite orientation can't really appear/evolve anymore since it can't compete against the existing much more complex life for those resources.
- SideburnsOfDoom 4y ago
  The mention the asymetry is here: "When the high energy protons in cosmic rays slam into the atmosphere, they produce particles called pions, and the rapid decay of pions is governed by the weak force — the only fundamental force with a known mirror asymmetry." Pion decay is apparently not symmetric. I don't know much about the topic, maybe start here: https://en.wikipedia.org/wiki/Weak_interaction#Violation_of_symmetry https://en.wikipedia.org/wiki/Weak_interaction#Violation_of_... It doesn't seem to be the case that "we don't have any cosmic rays with inverted polarization" - just that there is more in one direction than in the other. Even a slight bias would add up over time.
__MatrixMan__ 4y ago
Would this affect be the same in both hemispheres? Or would only one side get that handedness bias? My knowledge of the standard model isn't good enough to be able to puzzle it out.
photochemsyn 4y ago
Note the recently discovered Winchcombe meteorite had equal amounts of L- and R- amino acids, suggesting that non-biological processes produce both at the same rate, which is perhaps not what you'd expect if these cosmic ray or other physical processes were influencing L- vs R- handed molecule production/breakdown rates. https://news.ycombinator.com/item?id=33680493 https://news.ycombinator.com/item?id=33680493 https://www.science.org/doi/10.1126/sciadv.abq3925 https://www.science.org/doi/10.1126/sciadv.abq3925 It's likely life had to choose one or the other early on; imagine the mess it would be if you tried to build proteins or nucleic acids with a random assortment of left and right handed molecules, it'd be hard to get consistent structures. You'd have to have specific codons, the three-letter gene sequences that convert the 4-letter DNA code to the amino-acid code (22 for terrestrial life), for each handed version of the amino acids, so you'd need 44 different codons (out of 63 possible 3-letter combinations of ATCG) for the complete set, with no [little] overlap. [edit: it's 64, not 63! Today's life uses 61 for amino acids and 3 are reserved as stop signals. To get the full set in Python: set(list(itertools.permutations('AAATTTCCCGGG', 3))) ] I'd guess the early self-replicating systems (likely something like a RNA-protein ribosome complex capabale of self-replication using abiotically produced amino and nucleic acids) were only able to consistently replicate if they only used one enantiomer consistently, and it was just a roll of the die as to which one they settled on. There might even have been mixed populations of L-handed and R-handled life at the beginning, with only one branch surviving. Of course, that's the claim here, that of these two branches, one was more impacted by cosmic rays than the other. ???
- idlewords 4y ago
  This argument depends on whether there is a 'natural' biochemical scaffolding for life that resembles what we have on Earth. There's no reason in principle that a totally different biochemistry that made use of racemic mixtures couldn't work, but here we run into the wall of being unable to imagine forms of life substantially from our own. It's very easy to get into a loop of circular reasoning when answering questions like why life on Earth has a preferred handedness.
  - lumost 4y ago
iForgotMyPW 4y ago
[flagged]
supernova87a 4y ago
Is it me, or does the actual referenced ApJL paper, while having all the trappings of a scientific argument and an almost diarrheal collection of assorted physics references, basically boil down to a very extensively wrapped plausibility argument?
- iForgotMyPW 4y ago
  [flagged]
garbagecoder 4y ago
Lots of conjectures these days.
dang 4y ago
Discussed at the time: Cosmic Rays May Explain Life’s Bias for Right-Handed DNA - https://news.ycombinator.com/item?id=23688535 https://news.ycombinator.com/item?id=23688535 - June 2020 (56 comments)
jacknews 4y ago
It's interesting, but I don't think it answers the question. I believe life probably started as an autocatalytic set of chemicals which then 'discovered' they could use rna as a backbone/memory. So the reason for the chirality is at a lower level than discussed here. All just a hunch and IMHO of course.

88 points by deesep 4y ago

deleted 4y ago

[deleted]

platz 4y ago

I finally know what the definition of “evil” life is. Thank you.

xwdv 4y ago
When you look at the DNA of evil beings, such as the kinds you might pull through a portal to hell, you would find their DNA spirals to the left instead of the right. It implies hell is bathed in high energy rays with opposite polarization from the cosmic rays in our own universe.
- BuyMyBitcoins 4y ago
  If true, Hell is indeed a sinister place.
- nextaccountic 4y ago
  This also explains why left-handed people are identified with the devil. The whole universe is biased against being left-handed https://en.wikipedia.org/wiki/Bias_against_left-handed_people https://en.wikipedia.org/wiki/Bias_against_left-handed_peopl...
- h2odragon 4y ago
  It doesn't explain why the people on the other side of the portal favor goatee styled facial hair, tho. That is a deeper mystery.
- idlewords 4y ago
  The problem with this explanation is that the high temperature of hell would tend to racemize enantiomeric mixtures, and this process would easily dominate the very low cosmic ray effect.
fractallyte 4y ago
The origin of the word sinister... https://www.merriam-webster.com/words-at-play/sinister-left-dexter-right-history https://www.merriam-webster.com/words-at-play/sinister-left-...

bmitc 4y ago

The article never explains why right-handed polarization knocks electrons off right-handed helixes more often than left-handed ones. What's the mechanism there?

photochemsyn 4y ago
The linked paper has some clues: > "Muller (1927) that showed that the mutation rate is proportional to the radiation dose, much of it attributable to ionization by cosmic rays. The muon component dominates the flux of particles on the ground at energies above 100 MeV, contributing 85% of the radiation dose from cosmic rays (Atri & Melott 2011). Muons have an energy sufficient to penetrate considerable depths, and they are, on average, spin-polarized. Ionization by spin-polarized radiation could be enantioselective (Zel'dovich et al. 1977). Therefore, we argue that the mutation rate of live and evil organisms would be different. As there could be billions or even trillions of generation of the earliest and simplest life forms, a small difference in the mutation rate could easily sustain one of the two early, chiral choices." https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6 https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6 The actual models and calculations they employ to get an estimate of bias are really complicated, but if I read correctly, it's only a diffence of +/- 10^-7 relative to 50:50 equality: https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6#apjlab8dc6app2 https://iopscience.iop.org/article/10.3847/2041-8213/ab8dc6#... They suggest this is somehow amplified over time, but it's equally likely life just settled on one or the other handed version randomly.
- platz 4y ago
  you appear to have failed to understand the question that the questioner was asking.
  - photochemsyn 4y ago
    There are three models in the second link describing the possible mechanisms, none of them seem all that condensable. E.g. this seems to be at the center of one of their approaches: > "If we only consider second-order perturbations, involving two atomic sites in addition to O, the interaction cannot be geometrically chiral. So, if the fount is completely isotropic, we need to consider third-order perturbations, involving three distinct atomic sites, in addition to O, to have the possibility of a chiral coupling. Furthermore, it is apparent that the strength of the perturbations associated with each site is proportional to the scalar charges Q, and a third-order perturbation to the mutation rate will be simply proportional to the product of these charges, which is unchanged on inversion. It is only their relative locations that matter." > "There are several types of third-order perturbation. For example, we can use the first-order displacement due to the first charge to evaluate the electric field due to the second charge along the perturbed trajectory and compute a second-order velocity perturbation to calculate the third-order magnetic displacement at O. Alternatively, we can take the second-order displacement at O and combine this with the electric field due to a third charge to calculate a third-order change in the kinetic energy of the cosmic ray at O. We must then sum over all permutations of charge..." See also Fig B3: > "Figure B3. Example of electric chirality (barber pole model). The electric charge distribution of two biopolymers of opposite chirality projected onto a cylinder is shown, together with the unperturbed vs. perturbed trajectory of a magnetically polarized cosmic ray interacting with the molecule."

phyzome 4y ago

You could just as well say that the cosmic ray pions are more likely to destroy right-handed DNA, which would have the opposite effect. And I don't think essential mutations were particularly hard to come by in the primordial soup. UV light works fine, as do many, many chemicals. Or just more-primitive copying machinery. I don't think this weighs very heavily against the random symmetry-breaking hypothesis.

SideburnsOfDoom 4y ago
> You could just as well say that the cosmic ray pions are more likely to destroy right-handed DNA, which would have the opposite effect. You could, and it's going to be one effect or the other that is stronger - One of the chiralities will have an advantage due to this effect, relative to the other. And now we know which one.
- yyyk 4y ago
  >You could, and it's going to be one effect or the other that is stronger... And now we know which one. If the result would have been the other way around, we could have had here on NH the same story with the same argument with about the same conclusion. That's not very helpful. Note also the null hypothesis (none of these 'effects' matter, and choice is rather random) has the same non-explanatory potential as the story does.
thomastjeffery 4y ago
We already know the conclusion of this story: right-handed DNA is what exists today. The effort here is not to create a story blindly from known fundamentals into wherever that story might lead. The effort is to fill the gap in story from known fundamentals to a known conclusion. We don't know if other circumstances could have lead to another conclusion, and that would indeed be an interesting question to answer. But we do know that the conclusion we are living in somehow favored right-handed DNA. If this backstory leads to two potential conclusions - either left-handed or right-handed DNA, and not both - and we are already experiencing one of those conclusions (right-handed DNA), then it is OK for that backstory to be ambiguous. We don't need to prove the impossibility of the left-handed result. We only need to illustrate the impossibility (or unlikelihood) of both conclusions existing together at the end of the story.

tough 4y ago

As a leftie I wonder what cosmic rays did to me

Lapsa 4y ago
yeah, article initially reads somewhat confusing

Aardwolf 4y ago

The only thing that actually showed something asymmetric was, afaik, the image showing cosmic rays coming towards you with a certain magnetic polarization of muons. So if cosmic rays themselves would have had the other polarity (coming with N towards you and S away from you), then instead left handed would have been more advantageous? But, then, what's the reason why we don't have any cosmic rays with inverted polarization? Also, I think that even if the cosmic rays were not an issue and there was no advantage between left and right, only one of them would eventually survive: if there were both lifeforms with the left and the right orientation, they'd be competing for the same resources (while only being able to mutate/copy/evolve within their own type). Eventually one branch is bound to die out while the other remains, even if due to sheer luck rather than large advantage, and from then on the opposite orientation can't really appear/evolve anymore since it can't compete against the existing much more complex life for those resources.

SideburnsOfDoom 4y ago
The mention the asymetry is here: "When the high energy protons in cosmic rays slam into the atmosphere, they produce particles called pions, and the rapid decay of pions is governed by the weak force — the only fundamental force with a known mirror asymmetry." Pion decay is apparently not symmetric. I don't know much about the topic, maybe start here: https://en.wikipedia.org/wiki/Weak_interaction#Violation_of_symmetry https://en.wikipedia.org/wiki/Weak_interaction#Violation_of_... It doesn't seem to be the case that "we don't have any cosmic rays with inverted polarization" - just that there is more in one direction than in the other. Even a slight bias would add up over time.

__MatrixMan__ 4y ago

Would this affect be the same in both hemispheres? Or would only one side get that handedness bias? My knowledge of the standard model isn't good enough to be able to puzzle it out.

photochemsyn 4y ago

Note the recently discovered Winchcombe meteorite had equal amounts of L- and R- amino acids, suggesting that non-biological processes produce both at the same rate, which is perhaps not what you'd expect if these cosmic ray or other physical processes were influencing L- vs R- handed molecule production/breakdown rates. https://news.ycombinator.com/item?id=33680493 https://news.ycombinator.com/item?id=33680493 https://www.science.org/doi/10.1126/sciadv.abq3925 https://www.science.org/doi/10.1126/sciadv.abq3925 It's likely life had to choose one or the other early on; imagine the mess it would be if you tried to build proteins or nucleic acids with a random assortment of left and right handed molecules, it'd be hard to get consistent structures. You'd have to have specific codons, the three-letter gene sequences that convert the 4-letter DNA code to the amino-acid code (22 for terrestrial life), for each handed version of the amino acids, so you'd need 44 different codons (out of 63 possible 3-letter combinations of ATCG) for the complete set, with no [little] overlap. [edit: it's 64, not 63! Today's life uses 61 for amino acids and 3 are reserved as stop signals. To get the full set in Python: set(list(itertools.permutations('AAATTTCCCGGG', 3))) ] I'd guess the early self-replicating systems (likely something like a RNA-protein ribosome complex capabale of self-replication using abiotically produced amino and nucleic acids) were only able to consistently replicate if they only used one enantiomer consistently, and it was just a roll of the die as to which one they settled on. There might even have been mixed populations of L-handed and R-handled life at the beginning, with only one branch surviving. Of course, that's the claim here, that of these two branches, one was more impacted by cosmic rays than the other. ???

idlewords 4y ago
This argument depends on whether there is a 'natural' biochemical scaffolding for life that resembles what we have on Earth. There's no reason in principle that a totally different biochemistry that made use of racemic mixtures couldn't work, but here we run into the wall of being unable to imagine forms of life substantially from our own. It's very easy to get into a loop of circular reasoning when answering questions like why life on Earth has a preferred handedness.
- lumost 4y ago

iForgotMyPW 4y ago

[flagged]

supernova87a 4y ago

Is it me, or does the actual referenced ApJL paper, while having all the trappings of a scientific argument and an almost diarrheal collection of assorted physics references, basically boil down to a very extensively wrapped plausibility argument?

iForgotMyPW 4y ago
[flagged]

garbagecoder 4y ago

Lots of conjectures these days.

dang 4y ago

Discussed at the time: Cosmic Rays May Explain Life’s Bias for Right-Handed DNA - https://news.ycombinator.com/item?id=23688535 https://news.ycombinator.com/item?id=23688535 - June 2020 (56 comments)

jacknews 4y ago

It's interesting, but I don't think it answers the question. I believe life probably started as an autocatalytic set of chemicals which then 'discovered' they could use rna as a backbone/memory. So the reason for the chirality is at a lower level than discussed here. All just a hunch and IMHO of course.