Mitochondria Are Alive
mailyk | 638 points | 6mon ago | www.asimov.press
JumpCrisscross|6mon ago
Mitochondria are why I’m a Rare Earther.
In Earth’s history, mitochondrial endosymbiosis occurred once. Without that you don’t have the energy budget for complex life. Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been.
Until mitochondria, the emergence of life from nothing is plausible. With mitochondria, its progression to complex, multicellular and intelligent life makes sense. Both processes in small steps can be replicated, more or less, in the lab. But that one moment is not and has not been. As a result, I think the universe has lots of living slop but very few plants and animals.
(Aside, look at ATP go: https://www.youtube.com/watch?v=lUrEewYLIQg&t=939s)
jjk166|6mon ago
This process, known as primary endosymbiosis, happened at least twice, for mitochondria and chloroplasts. Further, while all chloroplasts (and more widely plastids) appear to share a common ancestor, there is evidence that mitochondria may descend from multiple lineages that underwent lateral gene transfer and/or convergent evolution. Nitroplasts are a likely another, separate instance of primary endosymbiosis.
There is also secondary endosymbiosis, where the endosymbiont organelles of one eukaryote are engulfed and incorporated into another eukaryotic cell to create a new type of endosymbiont. This has happened at least 8 times.
There are also theories that some other organelles are the product of other endosymbiosis events, many of which also have some of the hallmarks like their own genetic material. These theories are more speculative though.
It's also worth noting that while eukaryotes obviously gained some important capabilities from incorporating these endosymbionts, the endosymbionts they incorporated obviously managed to just evolve to perform those functions directly. Further, while one of eukaryotes' distinguishing features are mitochondria, there are several other major differences, and mitochondria are not believed to be what made eukaryotes better able to evolve complex multicellularity. Prokaryotes have indeed evolved multicellularity dozens of times, and we arbitrarily set our definition of complex multicellularity to distinguish from what prokaryotes have achieved.
Symmetry|6mon ago
The first time it happened involved a huge number of changes in the host cell, like the creation of a nucleus. That makes it seem more likely that an already eukaryotic cell can more easily incorporate other endosymbiotes.
Observation of prokaryote/prokaryote endosymbiosis would be real evidence against the rise of eukaryotes being the or one of the main limitations in the number of intelligent species in our galaxy.
jjk166|6mon ago
There's really only one change that mattered - phagocytosis. The ancestor of all was a prokaryote that practiced phagocytosis, the process of engulfing other cells. Endosymbiosis resulted from some of these engulfed cells not being digested.
There are no known modern prokaryotes capable of phagocytosis. Presumably the extinct prokaryotes who were capable, including those from the same lineage as the eukaryotes but which did not pick up mitochondria, were outcompeted by the eukaryotes who occupied the same niche.
Other changes like the origin of the cell nucleus and many other organelles can be readily explained by other malfunctionings of the phagocytosis process. Basically once you have the ability to pinch off parts of your cell wall into internal structures, you suddenly get a bunch of internal structures made of stuff that look surprisingly like cell wall.
hinkley|6mon ago
I believe there was an article here suggesting rather enthusiastically that nitroplasts are endosymbiots. Sometime in the Spring I believe.
__MatrixMan__|6mon ago
See also: nitroplasts
tasty_freeze|6mon ago
In addition to what others have pointed out (chloroplasts), I think this makes another mistake. Although only the mitochondria and chloroplast lineages remain, it is possible it happened other times but those lineages were out-competed, for whatever reasons, and are now extinct.
JumpCrisscross|6mon ago
> it is possible it happened other times but those lineages were out-competed, for whatever reasons, and are now extinct
Chlorophyll probably outcompeted retinal [1]. (The stuff in our eyes.)
The reduced form of my claim is that mitochondrial life so freakishly outcompetes its competitors as to be in a class of its own. Which still yields a rare Earth, albeit a first among many.
[1] https://en.wikipedia.org/wiki/Purple_Earth_hypothesis
jjk166|6mon ago
In an evolutionary process, one lineage running away is the most likely outcome. It's very unlikely that two competing lineages would evolve to be exactly equal at the same time and remain equal for an extended period of time.
JumpCrisscross|6mon ago
> In an evolutionary process, one lineage running away is the most likely outcome
What are you basing this on?
quantadev|6mon ago
It's based on the fact that one explanation of why there's not even millions more species of all life, is because the more successful ones simply cannibalized the less successful ones. This would've started even before complex life, almost at the chemical level.
I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later, so it came down to eat or be eaten. Still is frankly.
Jerrrrrrry|6mon ago
>I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later,
Species (maybe only [di?]morphic ones) rarely kill other instances of their own species, only maim - usually to the point of socially/reproductive shame/selective behavior; as infra-species violence is usually done for sexual signaling.
Like squirrels neutering each other, giraffes ruffling neck-fights, etc, it is not generally advantageous to actually hurt the opponent more than needed to signal dominance in a social hierarchy - this "gentleman" agreement is similar to all emergent collusion behavior exhibited by "free agents" in a limited pool; even without communication, the self-interested incentive to all follow a convergent rule will eventually emerge. Whether it be price fixing, social norms, or any other system where partially-regulated complex systems compete.
Additionally, for cannibalizing to be a positive-selective-trait, the species would had either adapted to eating the liver - the "resilience/filter" of a system, or had been "lucky" enough to identify/delineate/get repulsed by it.
Eating your own species liver would be nearly self-defeating-ly impossible from an evolutionary point of view and avoiding it but still eating your own species is too "taboo" (evolutionary artifact) of a benefit to ever randomly stumble into, especially against the benefits of 'good-sportsman-ship'.
smolder|6mon ago
> it is not generally advantageous to actually hurt the opponent more than needed to signal dominance
It is advantageous to beat a rival and take their energy even within a species. That's part of the whole 'survival of the fittest' thing. Preserving them for cooperation or something like slavery happens, but it's a rare strategy specific to intelligent animals like the GP implies.
quantadev|6mon ago
As Dawkins points out in `Selfish Gene`, it's the DNA sequence that's the evolutionary entity. For example, all mothers (and most fathers) protect their young even though it's a food source. Eating your own species (even children of other mothers) is counterproductive for the DNA itself, despite being productive for the particular copy of the animal doing the eating.
Jerrrrrrry|6mon ago
>reserving them for cooperation or something like slavery happens, but it's a rare strategy specific to intelligent animals
I should had clarified, this is lower, more intuitive behavior. It is not, which is why it arises emergently in lower-complexity/class systems.
>beat a rival and take their energy even within a species
And if done with literal, figurative, social, and complex "CLASS", it is literally sexy too!
National Geographic is entertaining for many dimensions of reasons.
Actually dismembering your sexual-rival and literally consuming their poor caloric conversion is pitifully inefficient compared to making them a sub-ling, whether it be via hen-pecking or innate dominance. It made sense before sexual dimorphication (moreso), but less so now.
Ladies like a gentleman, and gentleman's agreements are literally non-colluding emergent behavior to abide by unspoken higher-order rules for one's own explicit conscious self-incentive (lower order, high entropy), but also the implicit collective unconsciousness incentive (higher social order, lower entropy)
Both are reslience traits, which only emerge when selected for.
quantadev|6mon ago
I have no idea what you meant by liver. Maybe it's a biology term I'm unaware of. Certainly you didn't mean the organ. lolz.
Anyway, an interesting point about evolution is that things had to have been eating other smaller things long before the brain had enough processing power for "Species Recognition". It would've initially been a simple brain and rod/cone eye neuron and motor neuron in a fish that executed primary the rule of "See movement then execute tail wag, open mouth, close mouth" in that order. It takes like 5 neurons wired in a specific way to accomplish that. The first neurons had to have been that simple. Indeed the chain reaction of "input photon and convert energy into motor neuron charge potential" had to have been the actual chemical process that eventually developed the first neuron to begin with.
It was only after MUCH more evolution that avoidance of eating one's own species would've been possible by visual inspection of the prey. However, it's true it could have been a 'taste' signal where the scales of your own species had a bad enough taste that you spit it out rather than eating it, and that can be accomplished also with a brain of only a few neurons.
Jerrrrrrry|6mon ago
Liver/kidneys are organs where toxins are filtered, from the prey the predator consumes.
I am not a biologist obviously.
Because of the "food chain" actually being a pyramid, those organs contain the same "toxins" that are to be avoided, exponentially accumulating in whatever "organ" had the function to add resiliency by storing these toxins.
quantadev|6mon ago
Oh, I see. You expected people to infer "toxins" from the words "resilience/filter". Got it.
However, liver eating is a moot point regardless, because evolutionary theory would suggest eating toxins would have a bad taste/smell, so that organ would simply be avoided, while eating the rest. So it has no bearing on whether cannibalism happens or not.
Jerrrrrrry|6mon ago
>However, liver eating is a moot point regardless, because evolutionary theory would suggest eating toxins would have a bad taste/smell, so that organ would simply be avoided, while eating the rest. So it has no bearing on whether cannibalism happens or not.
We have nothing but confirmation bias and little time to test anything macro.
However, we do have contra-positives and the like; in this case, we (ourselves) avoid Liver in some animals, and notice the M.A.D-avoidance agreement among more socially-complex systems.
You shouldn't eat your young, you should eat your rival tribes young.
Especially because the young hand't accumulated much toxins yet, relative to the adults. And it is easier to bash babies over rocks than grown adults.
(per Carl Sagan)
Jerrrrrrry|6mon ago
yes, Q.E.D; the ambiguity of our lingua franca can be an "accumulate toxin" of sorts when trying to articulate higher-order ideas, as words (especially used as analogies) can carry implicit deprecated weight, and without the resilience of good-faith inference, can lead to misunderstandings, mis-alignment, or walking/talking write/right past each other.
quantadev|6mon ago
--or-- yes, when someone writes a very unclear sentence and then blames the reader for not understanding it...even going so far as to accuse the reader of bad-faith motivations.
Jerrrrrrry|6mon ago
>>> ...for cannibalizing to be a positive-selective-trait, the species would had either adapted to eating the liver - the "resilience/filter" of a system, ...
>I have no idea what you meant by liver. Maybe it's a biology term I'm unaware of. Certainly you didn't mean the organ. lolz.
>writes a very unclear sentence and then blames the reader...to accuse the reader of bad-faith motivations....
Did we both edit our posts....to improve accuracy, increase resiliency, and to compete ideas?
literally mesa-Q.E.D.
quantadev|6mon ago
You edited your post after first insulting me, then deleting the insult. Yes I saw it, but I removed my acknowledgment of the insult, only after you removed the insult. But you weren't done yet...just taking care not to have "flaggable" wording. Now it's more stilted language and Latin FTW. Did I miss anything?
Jerrrrrrry|6mon ago
nope, just demonstrated my point further-er-er:
neither of us had the incentive to either acknowledge our edits nor call the other out,
nor face the (perceived, social, higher-order) dissonance of being slightly unclear or "wrong" due to our own ego/self-interest (conscious, lower ordered self);
the emergent behavior then (gentleman's agreement) was to preserve our own ego's and not call out each other edits - which most people would never do, because:
our slightly varied ideas compete more fiercely for the same finite pool than other, completely niche-unrelated abstractions.
we are 4 layers deep now, but ill reduce for conciseness (for lurkers fwiw)
dont shit where you eat <- evolved trait to avoid waste-by products
dont hit a man when he's down <- highly effective altruism is still beneficial
morality is cowardice <- ties this all together from highest order (ego) to the id (fear of being replace)
we are now full circle.
quantadev|6mon ago
And now back to reality: I only edit posts to add an important point or fix a typo, but you edited your post to remove the insult it initially contained.
Jerrrrrrry|6mon ago
The insult was my inference that we should assume good faith, and that you had not done so (provably, by your 'lulz' snark); which you clearly did not show when assuming something other than the "liver" would be a organ of filtering toxins.
A decently display of faith should at least warrant a re-parsing of my (actually perfectly unambiguous) grammatical clarity, of which you implied was less than so.
Warrants the question, why not admit my posit:
That slightly-varied entities competing for the same/similar finite/limited supply pool of resources/demands will tend towards -- as an emergent behavior of both short-term disorderly self-incentivization and the stochastic long-term higher-order unconscious collective collusion -- the tendency to compete until dominance over **reproductive** rights are secured, but no more. The more fiercer the competition, the more selective the sieve, the more the dominant traits propagate: up to a plateaued point. Further complexity/order can than be more efficiently achieved by lessening the furiousity of the competition to a point of cooperation, which then innately lends itself to more hierarchy, efficient use of energy.
Take it from Roko the Replacer:
According to Sigmund Freud's psychoanalytic theory, the "fear of being replaced" is most closely linked to the concept of "castration anxiety," particularly within the context of the Oedipus complex, where a young boy fears his father will punish him for desiring his mother by castrating him, essentially rendering him "replaced" in her affections.
Free to continue discussion; but the under the Ego lies the Id, and I'm not well versed in that science yet, still approximating.
quantadev|6mon ago
The crux of the misunderstanding was that you assumed any reader would know a reference to liver is a reference to "toxicity" apparently based purely on the nearby words "resilience" and "filter". That was a flawed assumption, and ambiguous unclear writing.
Jerrrrrrry|6mon ago
Artifacts of evolution such as tribalism/xenophobia are the most obvious examples/analogs.
But really, and "slightly" varied instance of yourself is the "most" likely to compete for the same, infinite pool of resources.
smolder|6mon ago
The success of birds, bees, trees, plankton, mammals and so on. Many life forms have been rendered obsolete when the right adaptation comes along and forms a new branch.
jjk166|6mon ago
The second sentence of the comment.
aydyn|6mon ago
Does it yield a rare Earth? If we didn't have mitochondria and had something say 20% less efficient, why couldn't multicellular life still exist?
JumpCrisscross|6mon ago
> why couldn't multicellular life still exist?
We don't know the fundamental energy requirements of complex life. The threshold may be 2%. It may be 19.995%. If non-mitochondrial metabolism is common, the Earth would still be rare in that we'd be the "fast" biosphere. The high-octane species. Given how power-intensive intelligence is, that might be material. (Or it might not.)
More fundamentally: we have no plausible alternate chemistries that don't bootstrap on mitochondrial life. (We do for photosynthesis.)
addaon|6mon ago
> Given how power-intensive intelligence is
I’m not convinced there’s a reason to think intelligence is inherently power-intensive. Based on our limited samples, it’s certainly energy intensive, but there’s no reason it couldn’t be slowed down. In a world with less power available to life, one would expect speeds of e.g. predators and prey to be slower, allowing a slower intelligence to still provide an advantage.
JumpCrisscross|6mon ago
> not convinced there’s a reason to think intelligence is inherently power-intensive
Sure. But we know it empirically is. Our brains are expensive.
addaon|6mon ago
> Sure. But we know it empirically is. Our brains are expensive.
But our brains have mitochondria. As do our prey, and our predators. Is there any reason to suppose that the absence of mitochondria implies less potential for intelligence, instead of the potential for equal but slower intelligence? Mitochondria are about power production, not energy production -- they are a very dense source of ATP, but the reactions they use would provide equal energy even if less concentrated.
aydyn|6mon ago
I think that's a little farfetched since a lot of prokaryotes show the beginning stages of complex multi-cellularity.
jibal|6mon ago
I don't understand why anyone would commit to so adhering to a speculative hypothesis H as to call themselves an "H-er", especially one so pointless and vague as "Rare Earth". There is some probability that a random star has intelligent life on orbiting planets, but we have no idea what that probability is. The original "Rare Earth" proposal suggested that the Earth may be the only such planet in the galaxy, but at that rate there could be hundreds of billions of Earths.
rgbswan|6mon ago
> There is some probability that a random star has intelligent life on orbiting planets, but we have no idea what that probability is.
100%. The evolutionary pattern of our solar systems formation and earth ending up, temporarily, in just the right spot isn't rare but (was) a matter of time/timing.
Now one could argue that the stellar objects carrying specific components necessary for life did not hit every or many solar systems but every single simulation (in my head) of the big bang's aftermath reveals that it's at least multiple hundreds of thousands, given how much the observable universe has revealed so far in the places that we looked.
outworlder|6mon ago
Mitochondria seems to have been an 'accident', yes.
That does not mean that other lifeforms in different planets require mitochondria or equivalent organelles. As long as they can perform the necessary chemical reactions (which could be different in a different environments) and extract enough energy, they should be good.
How did mitochondria evolve in the first place? Could they have remained as independent organisms and use their massive energy budget to evolve independently?
JumpCrisscross|6mon ago
> long as they can perform the necessary chemical reactions
That mitochondria are conserved as an independent organelle across almost [1] all eukaryotes, across billions of years of history, suggests this is something the nuclear can’t easily in house.
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6343361/
outworlder|6mon ago
Maybe!
That could also suggest that any other strategies were just out competed by this one and lost the opportunity to develop further.
JumpCrisscross|6mon ago
> other strategies were just out competed by this one and lost the opportunity to develop further
Absolutely. It also means--however--that any niche where alternative did exist, when exposed to mitochondrial life, they lost.
Now that I think about it, it would be pretty funny if we're this universe's cheela [1], a freakishly overclocked biosphere that runs faster not because it had to but because it happened to.
[1] https://en.wikipedia.org/wiki/Dragon%27s_Egg
ajuc|6mon ago
Evolution is path-dependent. Notice that mammals were comprehensively outcompeted by dinosaurs till asteroid removed them and gave mammals time and niches to develop in. If you recreated dinosaurs right now they would lose to mammals (for example to homo sapiens).
It's perfectly possible that mitochondria are the dinosaurs of "cell powerplants" that just haven't encountered the asteroid to let other (ultimately better) solutions develop.
xeeeeeeeeeeenu|6mon ago
https://en.wikipedia.org/wiki/Monocercomonoides
>It is the first eukaryotic genus to be found to completely lack mitochondria, and all hallmark proteins responsible for mitochondrial function. The genus also lacks any other mitochondria related organelles (MROs) such as hydrogenosomes or mitosomes. Data suggests that the absence of mitochondria is not an ancestral feature, but rather due to secondary loss.
jamiek88|6mon ago
There are organisms without mitochondria too though. So it’s viable.
JumpCrisscross|6mon ago
> are organisms without mitochondria too though. So it’s viable.
True, it's an anaerobic ersatz cnidarian [1] that may be an escaped cancer [2].
[1] https://daily.jstor.org/who-needs-mitochondria-anyway/
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC6343361/
Rumudiez|6mon ago
> [discovered in] gut bacteria from a researcher’s pet chinchilla
wow. we could be surrounded by so many extraordinary organisms and not even know it because there's so much variety just in our own backyards
satvikpendem|6mon ago
There was a study where participants were asked to swab their belly buttons and lots of new organisms were found.
https://www.theatlantic.com/health/archive/2012/12/1-458-bac...
im3w1l|6mon ago
Absolutely fascinating. Especially the exotic multicellularity part. Maybe if it evolves even more multicellularity it will struggle with cancers of its own and have to reevolve tumor suppression, wouldn't that be something?!
mjan22640|6mon ago
The benefit of mitochondria is in the isolation of the high power reactions, that involve chemically aggressive elements, from the rest of the cell. That allows for high energy throughput without self damage. Cells that do not have mitochondria run the same or analogous power producing reactions, but at a much lower volume, to keep the damage sustainable. An alternative option to mitochondria would be to evolve some means for isolation of the power production.
pieter_mj|6mon ago
Mitochondria are bacteria that were endosymbioticized into what became the eukaryotic cell. Mitochondria can still survive (live) independently and functionally in the blood when they're separated from platelets and microvesicles. Mitochondria are the software that epigenetically switch nuclear DNA genes on and off. That sofware can be tweaked by light, for instance UV light or IR light. mtDNA mutates x1000000 more rapidly than nuclear DNA.
dekhn|6mon ago
uhh where did you get " Mitochondria are the software that epigenetically switch nuclear DNA genes on and off."
gus_massa|6mon ago
> Could they have remained as independent organisms and use their massive energy budget to evolve independently?
There are independent mitochondrial relative. They are mostly parasites that live inside cells.
From https://en.wikipedia.org/wiki/Mitochondrion
> The proto-mitochondrion was probably closely related to Rickettsia.
From https://en.wikipedia.org/wiki/Rickettsia
> Being obligate intracellular bacteria, rickettsias depend on entry, growth, and replication within the cytoplasm of living eukaryotic host cells (typically endothelial cells).
> Most notably, Rickettsia species are the pathogens responsible for typhus, rickettsialpox, boutonneuse fever, African tick-bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever, and Queensland tick typhus (Australian tick typhus).
liyamchitayat|6mon ago
One interesting thing is that many reactions actually have to occur in their own compartment- and since we have not lost the mtDNA, it may suggest that having an additional control center is beneficial.there are some interesting theories about the relations of that to lifespan https://www.cuimc.columbia.edu/news/mitochondria-are-flingin....
im3w1l|6mon ago
Couldn't it be that we haven't fully lost mtDNA because it's simply a very slow process that has not yet run its course?
aydyn|6mon ago
Given how old mitochondria are it seems more likely that its more efficient to have its own DNA.
DNA isn't just abstract information, it's also where the first step of protein / enzyme construction occurs. DNA location matters.
WalterSear|6mon ago
> Could they have remained as independent organisms and use their massive energy budget to evolve independently?
This presumes that their energy budget was massive to begin with, rather than being selected for over time.
Symmetry|6mon ago
It's more that cells can have large numbers of mitochondria than that teach produces a large amount of power. Prokaryotic cells can grow large, but because they respirate over their surface they are energy limited.
patcon|6mon ago
Mitochondria allowed who different energetic regimes and structures. Like the scaffold that allows multicellular organisms to even hold together simpler are not possible (energetically) without mitochondria. It took the whole marriage of the two systems to allow the energy state (the "chemical reactions" as you say) to be possible
SFI Complexity podcast has a few great episodes on this
smolder|6mon ago
Right, the requirement for life is an entropy gradient sustained long enough as well as the right materials present to capture that.
eboynyc32|6mon ago
It’s so pathetic to keep hearing that dna is an accident , life is an accident, mitochondria is an accident. What is an accident that natures says “oooops”. When will we take our heads out of the sand and realize the universe is alive and creating everything. There are no goddamn accidents !!!!
AlphaEsponjosus|6mon ago
What? When saying that "X" is an accident, nobody means "nature says 'oooops'. Nature is neither conscious nor alive, if universe were alive and creates and shapes life, why is there so many errors happening in the universe?
Everything exist by " accident", and that means that is the result of random events that happen unexpectedly in unimaginable places, leading to an environent were the outcome of this events causes more random events.
Why universe insist in making life so uncommon if it has the secret to create and replicate?
jibal|6mon ago
People whose heads are out of the sand reject that misunderstanding of the universe and nature, neither of which are agents.
exe34|6mon ago
all happy little accidents!
qudat|6mon ago
Like other gradients (heat, pressure, chemical) it might seem rare, the gradient guides its occurrence. A power efficiency gradient was going to happen eventually, accident or otherwise.
hughesjj|6mon ago
Yup. That it happened isn't by chance, but the particular instance being the one to happen & dominate is by chance.
casenmgreen|6mon ago
I may be wrong, but I recall reading recently it had been found the same event had occurred again, fairly recently (hundreds of thousands of years, could be millions) in some species of bacteria or something like that.
Here's a thought, also; maybe once this has happened, it tends to crowd out needing to happen again.
JumpCrisscross|6mon ago
> it had been found the same event had occurred again, fairly recently
Would love to know the source if you have it.
joshuahedlund|6mon ago
Might be referring to this: https://newatlas.com/biology/life-merger-evolution-symbiosis...
casenmgreen|6mon ago
Huh. This is the correct news, but a different article to the one I recall. However, very interesting;
> The first occurred about 2.2 billion years ago, when an archaea swallowed a bacterium that became the mitochondria.
> The second time happened about 1.6 billion years ago, when some of these more advanced cells absorbed cyanobacteria that could harvest energy from sunlight.
> And now, scientists have discovered that it’s happening again. A species of algae called Braarudosphaera bigelowii was found to have engulfed a cyanobacterium that lets them do something that algae, and plants in general, can’t normally do – "fixing" nitrogen straight from the air, and combining it with other elements to create more useful compounds.
So, tremendously rare, at least to our knowledge at this time, but not a one-off.
casenmgreen|6mon ago
Yes. That's the one. Thank you.
aardvark179|6mon ago
Chloroplasts also evolved from separate organisms and are now effectively organelles. So this is t a one off event.
ASalazarMX|6mon ago
And even if those hadn't become organelles, who knows if they (or mitocondrias) could have evolved towards multicellular life on their own? They were already organisms to begin with.
liyamchitayat|6mon ago
Yes! and there are additional cases, like the nitroplasts that we recently discovered. https://en.wikipedia.org/wiki/Nitroplast
quantadev|6mon ago
All planets with a diverse chemical makeup will stumble across accidental formation of a replicator molecule. It's 100% certain. That's all that's required for "life".
People have theorized even a 50 base pair segment of RNA might be capable of building exact copies of itself, either by snapping in half and auto-forming the same other half, or by other means. Since there's two sexes, it was perhaps a "halving" at that level, that early on, which led ultimately to TWO sexes, but that's a side point.
We can even predict the probability of any 50 base pair ordering. It's 1/(4^50). That's 30 zeroes in the denominator. Now consider that a single glass of water has 10^23 molecules. That's 7 orders of magnitude difference. So the amount of water you need to cross that magnitude threshold is 7. Turns out that's exactly the size of an Olympic swimming pool. 10 million cups of water.
So statistically, a planet with an ocean volume only as large as a swimming pool has the "Statistical Power" (power of large numbers) to find ANY 50 base pair combination (give or take an order of magnitude or two) Once it finds a replicator, life has started, and so has evolution. And that's guaranteed within the first minute or so, at reasonable temperatures. Now multiply that time by the average age of a planet, and you begin to realize, statistically life is guaranteed, in any chemically diverse scenario with reasonable temperatures.
dekhn|6mon ago
Interesting argument, but nobody believes that a diverse chemical makeup is sufficient to guarantee life.
You can wave big numbers around but none of that makes a convincing argument; it's not hard to construct any number of scenarios where self replicators are started but don't lead to true life.
Also you're comparing a gram of water to a bunch of bases; H2O is not DNA.
quantadev|6mon ago
Sure we don't have proof that all life will form from essentially "binary" data, (although technically ours is made of 4 bases, not 2), but it's almost axiomatic that life will find the simplest possible way to store information before it finds the more complex ways. Ergo DNA is almost binary, but quarternary instead. It's nearly digital.
Insofar as your H20 vs DNA comparison, I merely used water as a way to show relative "scale". That is, HOW MUCH fluid volume (relative to the order of magnitude of size of atoms) would it take to contain the requisite number of RNA. Because when it comes to probabilities of finding astronomically unlikely combinations, astronomically large numbers is key. I think in a mole of random Rubicks cubes, hundreds will be "accidentally solved" (I forgot those numbers, so check my math, on that one)
The reason I threw in the "give or take 2 orders of magnitude" caveat was precisely because I knew someone like you would accuse me of relating H20 to RNA in a way in which I didn't. Other planets will have different atoms, not necessary water-based life, but planets even the size of a swimming pool have the "numbers game" power to create life.
dekhn|6mon ago
Are you aware that at high concentrations, DNA, RNA, and proteins all have serious problems? For example, DNA and RNA are highly charged, with strong repulsion effects, while also having large greasy areas. At the concentrations you're describing, the DNA and RNA would not be functional as we know it.
quantadev|6mon ago
Right. The "thought experiment" math is a tight packing of theoretical RNA molecules, and not intended to be taken literally, without a dilution factor; but only to show [some] people their intuition is WAY off about the power of large numbers to "create" unlikely patterns.
For example, if you ask most people how many randomly occurring Rubiks Cubes will just be accidentally solved even with Avogrdro's number of them, their answer is usually zero; and unsurprisingly they're the same ones claiming there had to be a God to create even the initial replicator.
QuiteSocialized|6mon ago
For this to hold, each of those water molecules in that swimming pool needs to somehow turn into a random 50 base pair chain of RNA.
Those RNA molecules are also going to be ~two orders of magnitude larger than a water molecule, so you're going to need a bigger pool...
To actually replicate, some loose ingredient molecules must also be present, and in reasonable quantities to be at hand in any given place in the pool.
The argument you are actually making is that a vessel that is filled with randomly assembled chunks of RNA not shorter than 50 base pairs each, the quantity of which equal the number of molecules of water in an Olympic pool, would contain life with probability ~1.
Now, the ocean is large, and a billion years is a long time, but I'm a long way from convinced that the chance of life is 100% on any given suitable planet.
quantadev|6mon ago
That's a decent analysis of the things this "thought experiment" doesn't address. I'm not a chemist but I think in a sea of AT and GC pairs even mixed with water, the ability to find every random sequence possible is near certainty:
Especially when you multiply by the number of swimming pools of all ocean water (10^14) by the number of minutes of the history of Earth (10^15), and consider that the probability of the accidental 50 base pair replicator forming needs to have those 29 extra zeroes, in the numerator (not the denominator). So the likelihood, now that I add more info, has just gone up 29 orders of magnitude. lol. (BTW. the 1 minute assumption will be temperature dependent, and is a guess at how long it takes reactions to take place).
The whole thing is a rough approximation like the Drake Equation is, and each number is an estimate. If you want to attack the Thought Experiment, at it's weakest point, just question the initial assumption, which is the biggest guess of all, that some unique 50 base pair RNA can replicate itself.
UniverseHacker|6mon ago
There are a huge number of different organelles that evolved independently through events like this- other people mention chloroplasts but there are many others, and probably many yet undiscovered.
I would argue that the type of event that produced mitochondria is likely not rare at all, but certain pairings will so outcompete others that we should expect only one to survive and dominate.
WWWWH|6mon ago
I have a chloroplast for you on line two; can you hold?
JumpCrisscross|6mon ago
They're sensitive about the Oxygen Holocaust [1][2]?
ordu|6mon ago
> Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been.
I don't think it is a very persuasive argument, because it is possible that modern microbiology has defenses because it has mitochondria. I know almost nothing about cells from a few billions years ago, but it seems plausible to me that they were ambivalent towards intrusions of other cells, it can be beneficial or disadvantageous depending on an intruder. Moreover beneficial intruders could give a lot of evolutionary advantage, not like today, when all important things (like mitohondria) are already here. In theory, bacteria could benefit a lot, but there are no ecological niches for a bacteria with mitochondria, all are claimed by some eucaryotes, which are highly adapted.
It is a very common thing in evolution. For example, there are bats, but they cannot evolve and replace birds, because there are birds. Bats have their niche, but they cannot outcompete birds at being more birds than birds. If they were given a chance, then maybe they could try to catch up with birds, but they didn't have a chance and they will have it only if some cataclysm will wipe out birds and leave bats.
hshshshshsh|6mon ago
If reality can emerge out of nowhere I don't see it unlikely for life to emerge in some other planet.
JumpCrisscross|6mon ago
> If reality can emerge out of nowhere I don't see it unlikely for life to emerge in some other planet
If everything however unlikely is likely because creation is unfathomable, sure.
hshshshshsh|6mon ago
Not everything. Life in particular. Because without life (a conscious observer) reality cannot exist. So it should be a property of reality for life to emerge.
9dev|6mon ago
Isn't that kind of mixing up the chain of causation? Without a winner, a lottery cannot exist (or at least, at p=0, it's nonsensical). That doesn't automatically imply there are a lot of winners, however.
hshshshshsh|6mon ago
I think what I am trying to say is consciousness (life) is reality. And so all kind of planetary experiences can exist inside consciousness as it's contents since consciousness is capable of generating all kind of content.
There is nothing specific about our consciousness that makes it unique to earth.
dekhn|6mon ago
Your philosophy is consistent with panpsychism (https://en.wikipedia.org/wiki/Panpsychism). Not really clear how this affects the major discussion here, which is about objective reality as determined by science, and so far as we can tell, neither life nor consciousness is not a prerequisite for reality. It's a fun idea to play with but firmly outside the realm of something we could experiment with scientifically.
timschmidt|6mon ago
You are mistaking the map for the territory: https://en.wikipedia.org/wiki/Map%E2%80%93territory_relation
hshshshshsh|6mon ago
Can you explain in simple terms? I see physical reality as almost redundant and consciousness seems to be able to do everything.
timschmidt|6mon ago
From the first paragraph of the linked article:
"Mistaking the map for the territory is a logical fallacy that occurs when someone confuses the semantics of a term with what it represents. Polish-American scientist and philosopher Alfred Korzybski remarked that "the map is not the territory" and that "the word is not the thing", encapsulating his view that an abstraction derived from something, or a reaction to it, is not the thing itself. Korzybski held that many people do confuse maps with territories, that is, confuse conceptual models of reality with reality itself."
hshshshshsh|6mon ago
Okay. I can see that in day to day life. People confusing sentences with actual knowing. Like labeling something a tree and thinking you know what a tree is because you know it's a "tree".
But how did anyone verify there is an underlying reality outside consciousness? It's just an assumption right?
dekhn|6mon ago
Yes, it's taken on faith by scientists that we live in an objective universe with cold hard reality outside our consciousness. It seems like a reasonable assumption, consistent with all our observations. It seems not unreasonable to assume that in the early universe there was nothing living, then at some point, through random chance, the first living things became alive (possibly from some non-alive replicators), and then later, the first living things with consciousness came to be. Again, all of this is consistent with our observations, but effectively taken on faith/treated as an assumption.
timschmidt|6mon ago
> But how did anyone verify there is an underlying reality outside consciousness?
It's the stuff which continues existing when we stop believing in it.
WalterSear|6mon ago
A 'quantum observer' is merely a physical system that interacts with the quantum system being measured. It doesn't have to be conscious or animate.
dekhn|6mon ago
There is no known scientific principle or theory with experimental support that without a conscious observer reality cannot exist. It's not something that can be tested, and lies in the realm of philosophy, not science.
hshshshshsh|6mon ago
I don't think reality has this property that what cannot be tested through scientific method is not true.
dekhn|6mon ago
It might not, you wouldn't be able to convince anybody that something is true, but cannot be tested- that's philosophy and religion.
hshshshshsh|6mon ago
I think David Deutsche has this idea that the best explanations should be treated as true even if you can't test it.
thrw42A8N|6mon ago
That sounds like a catch-22
Anotheroneagain|6mon ago
Only if you assume it went the seemingly straightforward way, but it could have been more complex. Maybe at first there was no particular limit to unicellular life, and there were unicellular lifeforms both small or large. But the big ones had a terrible problem avoiding getting parasitized by microscopic ones. As, there is one wall to breach, and once it gets in, it's in for good. So maybe eventually one of the bigger ones developed multicellularity as a kind of internal defence wall system, rather than multicellular life evolving from tiny cells clumping together. This gave it an enormous advantage at larger sizes, as all pathogens had to invade the cells one by one, and most of the macroscopic unicellular organisms perished, and some unicellular eukaryotes evolved since then.
ricksunny|6mon ago
Robin Hanson #HardSteps
https://m.youtube.com/watch?v=0lKliaFllPA&t=910s (timeatamped)
jibal|6mon ago
Earth is so rare that there might merely be hundred of billions of others (say, one per galaxy).
zero_bias|6mon ago
There are a lot of sub Neptune planets, the reason why there are only a few earth alike planets is just lack of powerful telescopes and observation time. As technology improves, we’ll find much more planets like ours. Earth is not unique in any way
VMG|6mon ago
How do we know it only happened once? Maybe it happened multiple times but only one version survived while the others were outcompeted?
JumpCrisscross|6mon ago
> How do we know it only happened once?
We don't. But we know we can't replicate it, have never observed it, don't seem to find half-assed attempts at it in the wild and that there weren't multiple competing chemistries that found themselves co-existing, there was one.
stoperaticless|6mon ago
I would like to present you with Chlamydia.
I find it remarkable that chlamydia cells, fully enter host cells and live there stealing of resources.
I would call it evolutions “half-assed attempt” at endosymbiosis. (Disclaimer: evolution has no goal)
hurpdurpdurp|6mon ago
I know nothing about biology, pardon my ignorance. From the article it sounds like mitochondria were a separate organism that has perhaps simplified through specialization and is currently on the boundary of being an independent life form. It also sounds like there are other structures (golgi apparatus are mentioned?) which are not on the bubble. Are we sure that there is not an arrow of time here, where once those other structures were also semi-independent and have become less so?
More broadly, it leads me to wonder whether cellular life might eventually/might have at some point specialize towards hosting novel endosymbioses.
Either scenario, assuming what I'm saying isn't just total nonsense, would seem to make the state of mitochondria less of a one-off event and more of the instance of that event we are around at the right time to observe.
liyamchitayat|6mon ago
Hi! thanks for taking time to read :)
Those other membrane bubbles inside out cells don't have any of the machines we expect to be associated with cellular life- but you never actually know!
Also, this is def not a 1-off, and happened many times, including chloroplasts in this new nitroplast we found https://en.wikipedia.org/wiki/Nitroplast
maxerickson|6mon ago
So only a few billion planets with complex life?
JumpCrisscross|6mon ago
> only a few billion planets with complex life?
Or trillions or tens or ones. Depends on what number you put in the exponent. Currently, we don't have useful constraints on that figure.
(A lot of popular astrobiology pulls the "if we could only get 1% of the market we'd be billionaires" schtick.)
dylan604|6mon ago
The astrobiology schtick is just a what if thought experiment though, and nothing proven nor claimed to be fact. It's just a way to show that the scale of the universe is "hugely, mind-bogglingly big" while trying to pull a number that our squishy lobes could comprehend. If 1% of mind-bogglingly huge number, then 1% of that, then 1% of that yields a still mind-bogglingly big number. The laws of large numbers would suggest something as well. Otherwise, "its an awful waste of space"
JumpCrisscross|6mon ago
Sure. The point is 1% is a huge fraction for a lot of things. Market share. And many reaction cross sections.
meneton|6mon ago
This article is framed as if there is something novel and profound here, but the "aliveness" of mitochondria is simply a matter of how we choose to apply the label "life" - a human linguistic construct that exists independently of the biological phenomena. This is not a new discussion - science has been considering this question for many decades, just as it has with viruses. These all come down to arguments about semantics and don't add anything to the science.
Mitochondria are fascinating and there is still a huge amount to learn about them but they are totally dependent on the cell's machinery. Most of their genes, the code for their structure, are in the nuclear DNA. A glaring omission if you are trying to make the case that mitochondria are independently living. My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
The implication of the whole article is that there something we have missed. This really isn't the case. Lynn Margulis's endosymbiotic origin of mitochondria was challenged by many, and it did spark a scientific debate - that's how science works. She won the argument comprehensively decades ago and is well established science. There have been many such endosymbiotic events in the history of life - there are subfields of evolutionary biology that study these processes.
beambot|6mon ago
> These all come down to arguments about semantics and don't add anything to the science.
This accurately describes much of science...
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
The cells that comprise your heart are very much alive, but they will die without support infrastructure. They live, they replicate, they die -- like every cell in your body. If I relocate you to the moon without support infrastructure, you would die too -- and yet (I think?) you are probably alive.
incompatible|6mon ago
"Very much alive," in the sense of being a living organism in their own right. By that standard, each cell in the human body can also be considered a separate living organism, simply cooperating with other humans cells in a complex way. It makes sense, since we have no problem identifying the trillions of bacteria cells living on or in the human body as separate living organisms.
dukeofdoom|6mon ago
"Sperm and egg cells, known as gametes, fuse during fertilization to create a zygote. "
Since all humans were just 2 cells at one point. It seems to follow that the entirely of the code for what a human is, is contained in just those 2 cells. Not just code for a finger. But even code for our deeply ingrained fear of snakes. Was just at one point contained in those 2 cells. Kind of blows your mind.
If they are separate living organisms, then there seems something recursive about humans if they can be just 2 cells at one point.
tsimionescu|6mon ago
I know this is not exactly your point, but it's important to remember that it's not exactly everything. The intra-uterine environment has a serious contribution to your development, and almost certainly transplanting the fecundated cell into a different mother would lead to a different person being born. Especially when it comes to things like intestinal flora, which mostly seems to get "seeded" from the mother during birth. Even the milk you ingest after birth significantly influences certain aspects of your basic biology (mostly the immune system).
erikerikson|6mon ago
No. The expression of genes is controlled by their environment. We are products of both nature and nurture.
positus|6mon ago
[flagged]
lisper|6mon ago
> everything that they will be when fully grown is contained there in that tiny little life
No, that's not true. Those two cells require a lot of care and nurturing and education before they become a person.
Have you heard of HeLa cells?
https://en.wikipedia.org/wiki/HeLa
They have a full compliment of human DNA, but no one in their right mind would argue that they are a person.
[UPDATE] This pithy slogan just occurred to me: a zygote is a person like a set of blueprints is a house.
Jerrrrrrry|6mon ago
[flagged]
nitwit005|6mon ago
They're as much a human as some living cells I shed on the floor. Alive and genetically human.
Being a person involves some level of thought, not just existing. If you ripped my brain completely out, and kept my body alive, most would consider the brain removal the time of death. That's when the person they knew died.
jyounker|6mon ago
When you get a scrape and you bleed, thousands of your cells burst forth and die. Each has the same set of information necessary to rebuild an entire person. Have you committed mass murder?
maroonblazer|6mon ago
The strongest arguments against abortion don't hinge on whether the fetus is a person. The question of abortion ultimately boils down to whose rights we privilege: those of the mother, or the fetus?
Thiez|6mon ago
Why would the fetus have any rights that are not automatically defeated by the rights of its mother if it's not a person? All anti-abortion arguments that I'm aware of start by arguing that the fetus deserves the rights of a person, and then proceed from there. Could you present a counterexample?
maroonblazer|6mon ago
Sure, a couple I've come across:
"Potentiality" - this view argues that regardless of whether the fetus is a person, it has the potential to become a person, and thus inherits some moral consideration.
"Value of Human Life" - the argument that human life - at any stage of development - has intrinsic value and thus should be protected.
ants_everywhere|6mon ago
Heck, a sperm and an egg in separate containers have exactly the same information as a fertilized egg. That's a powerful argument for having a clear idea of what creates moral personhood.
Otherwise you're in the same camp that believes a sky daddy breathes a soul into your baby at conception and that IVF is the work of Satan.
incompatible|6mon ago
In that case, it would also be a good argument against killing any single-celled organism, since it's a life that already exists. But life on Earth is cheap.
TheHegemon|6mon ago
Are miscarriages then involuntary manslaughter?
nwienert|6mon ago
If the miscarriage was caused by reckless or criminal negligence
moomin|6mon ago
There is a lot more to a person than genetic code. We are not IKEA chairs and DNA is not the assembly instructions.
dukeofdoom|6mon ago
I don't think that DNA is just procedural assembly instructions. Though maybe more akin to something like the encoding of a neural network. Granted I have a basic understanding of DNA.
cdetrio|6mon ago
Maybe you saw this paper about that idea - The Genomic Code: The genome instantiates a generative model of the organism.
"Here, we propose a new analogy, inspired by recent work in machine learning and neuroscience: that the genome encodes a generative model of the organism. In this scheme, by analogy with variational autoencoders, the genome does not encode either organismal form or developmental processes directly, but comprises a compressed space of latent variables."
1. https://arxiv.org/abs/2407.15908 2. discussion with the authors https://www.youtube.com/watch?v=6QaMnUBkmz4
larodi|6mon ago
Yeah?! You think so? Perhaps yours a strong argument against consumption of anything born this way, renders all meat consumption a bad thing with these same arguments… I bet 5€ you had your burger this morning and it had plenty of already dead cells in it, not to account for the yeast in the bread…
antonvs|6mon ago
> From the moment the egg is fertilized, a new person exists.
The potential for a new person exists. Just as the potential for new people exist in a collection of sperm and egg cells.
The only difference, which you seem to be latching onto, is that now that potential has been turned into a more specific one. Why do you think that makes any real difference? It seems like an arbitrary and abstract argument that depends on an almost mystical perspective.
> This is a strong argument against abortion.
It really isn't. In fact, it's fallacious, because to accept the argument, you have to accept premises that produce the desired conclusion - i.e. it's question-begging, assuming its conclusion.
Jerrrrrrry|6mon ago
You are correct and for this: you are not going to be rewarded for it.
The cognitive dissonance is too strong, this entire subject should honestly be banned from HN.
RajT88|6mon ago
It would be a so-so argument if it was true. (It is not) How DNA is expressed is a part of the story as well which involves many environmental factors both in utero and after birth.
We do not totally understand how it works, but there are heritable traits not passed via DNA - the one often in the news is women with emotional trauma pass that trauma on to their children, and those children show those symptoms even if raised in a happy home with 0 contact with the mother.
It is a philosophical argument, not a scientific one. One which if we try and reason based on how special nature treats embryos quickly falls apart anyways...
jyounker|6mon ago
For the most part epigenetic traits seem to be transmitted by DNA too. Rather than being encoded in the pattern of base pairs, the epigenetic changes are made by slightly modifying the structure of individual bases. Think of it as adding tags to instructions.
RHSman2|6mon ago
If something dies surely it was alive once?
amelius|6mon ago
> This accurately describes much of science...
It is more related to the philosophy of science.
https://en.wikipedia.org/wiki/Philosophy_of_science
Jerrrrrrry|6mon ago
More like:
https://en.wikipedia.org/wiki/Ship_of_Theseus
partomniscient|6mon ago
Built with his grandfathers axe.
P.S. I'm not implying his grandfather was Gimli even if Gimli theoretically had two grandfathers.
HappMacDonald|6mon ago
One might say "natural philosophy"
svnt|6mon ago
Natural philosophy is what science was called before it was called science.
The philosophy of science is something that has only existed since the practice of science became widespread.
colechristensen|6mon ago
The final categorization is the least interesting part though. If we understand the origins and mechanics of how the once parasitic organism became an integral part of almost all complex life, does arguing the semantics of what label you put on it really add much value?
To reframe it: what you’re really doing is arguing about the definition of alive. In this case my opinion is: who cares. I fail to see how expanding the definition or being precise here adds anything.
opello|6mon ago
> does arguing the semantics of what label you put on it really add much value
Refining the definition of something often helps provoke new understanding and tests of the limit of that refinement. It seems like a critical requirement in the "form a hypothesis" step of the scientific method.
rgbswan|6mon ago
i might be wrong but corporations/institutions never sponsor R&D in all directions so framing/phrasing is vital. but, from a philosophical pov, I agree with you.
opello|6mon ago
> If I relocate you to the moon without support infrastructure, you would die too -- and yet (I think?) you are probably alive.
It seems to me that the alternative to people being alive quite quickly reduces to nothing is alive by way of information theory.
lupire|6mon ago
Life is not binary.
staplers|6mon ago
Best argument I've heard for Gaia theory, intentionally or not.
TeMPOraL|6mon ago
We probably can keep a heart alive outside of body, through artificial means, for minutes, maybe hours - and I mean keep it functioning, not just chilling it to slow its death. It's plausible we'll learn to be able to keep it alive for days, months, years, decades. At which point we could say that the "supporting infrastructure" of the rest of a human body isn't necessary for the heart to be independently alive?
What if we do it all on the Moon, or Mars? How does Gaia feel about it? We already know that it's theoretically possible, if not yet achievable in practice, to create artificial environments capable of supporting human life indefinitely - or, on a long enough timescale, bootstrap an independent, self-sufficient biosphere. The two are, in the limit, the same thing anyway.
Or are we going to argue that human technology is, by extension through causality, a part of life on Earth, and therefore a part of Gaia itself? Is Gaia in all of us, and will it persist after Earth dies if humanity is still around somewhere else?
All in all, I suppose the correct definitions of terms are the ones that are most useful in a given context :). "Categories were made for man, not man for the categories", and all that.
staplers|6mon ago
At which point we could say that the "supporting infrastructure" of the rest of a human body isn't necessary for the heart to be independently alive
dr_dshiv|6mon ago
I’m not sure what you are arguing against. For me, the article offered a lovely reminder that life is special. Life involves mechanisms but it is more than a machine. And with an attitude that our lives our symbiotically bound to another living organism (or 10^17 of them) we gain a valuable humility — one that might afford us new perspectives on how to make them all happy and flourish. That’s the promise— not just a spiritual connection to the aliveness of mitochondria, but a pragmatic orientation towards their health and wellbeing. And there is a lot of scientific opportunity to explore there.
meneton|6mon ago
As I said in another comment, I think that mitochondria are fascinating, understudied and a rich area for research.
We are bound to the myriad other pieces of DNA that all have different evolutionary histories within us, we are symbiotically bound to many strands of life on many levels. We are just one strand, a part of a singular whole, bound to all strands of life beyond us. This view of life led me to science. I totally think that this view of biology is not properly appreciated by most scientists.
But this article was presented as a scientific piece and made the explicit claim that mitochondria were alive which is a semantic argument that doesn't have a scientific answer.
It is a well written piece that made it to the top of hacker news and it's great to see the debate.
But it just isn't true that mitochondria are alive by our currently accepted definition of alive. This is an old debate in biology that was settled years ago. There is nothing in this paper that wasn't known to mainstream science decades ago, but it is presented as a novel scientific viewpoint.
dr_dshiv|6mon ago
> it just isn't true that mitochondria are alive by our currently accepted definition of alive. This is an old debate in biology that was settled years ago.
Sorry, but that’s an overreach. There are many “accepted” definitions” of life across different scientific fields. According to Wikipedia, there are at least 123 definitions of life — and there is not scientific consensus. Mitochondria are alive based on some definitions and not alive based on others.
https://en.wikipedia.org/wiki/Life
Expecting life to have total autonomy in self-sustainability is absurd. Otherwise somatic cells or even people would be not alive.
And the argument that mitochondria are not alive because they can’t encode all their own proteins — well, I’ll point out that humans can’t produce all amino acids, either. As a thought experiment, if humans couldn’t produce a certain essential protein — and had to rely on a symbiont, would that mean humans weren’t alive?
Finally I’ll point out that Mitochondria can be healthy or flourishing — and they can be sick and die. How can something that is not alive, die?
It’s ok to argue for a narrow definition. But please don’t present this argument as though you are the defender of clear scientific conclusions. There simply isn’t consensus on this across the sciences.
meneton|6mon ago
I agree I didn't phrase that right. It was a short cut.
There has been debate over whether mitochondria can be called alive since at least 1890. For many years the vast majority of mitochondrial biologists have avoided the binary alive/not alive classification because there is a spectrum of 'livingness' and we can draw the line anywhere we like.
Picking a different line position is not scientific, it is semantics. What do we mean by the term 'alive'?
The article presented a profound new way of viewing the living state of mitochondria that was going to transform the world. It said nothing new, and failed to make any reference to the long term debate.
But it was a nicely written interesting article and mitochondria are going to be hugely important therapeutic area in the future.
jsvlrtmred|6mon ago
I think they are arguing against the subtitle of the article: "Recognizing that mitochondria are alive will open new horizons into how we learn about, and build with, biology." Which seems a stretch based on semantics.
aeturnum|6mon ago
> The implication of the whole article is that there something we have missed.
I think this article is talking to people who haven't internalized the details of the scientific consensus. Those people are still going around, talking about "life" and making decisions based on the flawed understanding this article is critiquing. I think it's likely that the thing that "has been missed" is not narrowly scientific in the way you seem to be thinking - but more about broad implications and worldview.
meneton|6mon ago
I am not sure what exactly the 'broad implications and worldview' are here that are being challenged. The article is presented as a scientific opinion and references scientific research and has a doi number for citation (Cite: Liyam Chitayat. “Mitochondria Are Alive” Asimov Press (2024). DOI: https://doi.org/10.62211/38pe-75hu). What do you think that the article was challenging?
legel|6mon ago
Obviously the article is challenging the view — scientific or not — that mitochondria are not living.
Side note: previously I was funded by NSF and NASA to study such questions from biophysics and astrobiology.
That said, this was a delightful read. I did not realize or conceive of mitochondria as, like bacteria in our bodies, independent living networks with unique genomes, evolution, and flows of information and energy.
Reading about the health benefits of “external mitochondria” made me think about when I hug my dog: are we exchanging mitochondria, perhaps?
Jerrrry|6mon ago
Life is just an arbitrary number of magnitude of complexity
thinkling|6mon ago
> Most of their genes, the code for their structure, are in the nuclear DNA.
Are they? I was under the impression that mitochondria are closer to pseudo-cells living inside human cells.
Wikipedia seems to confirm this [1]:
> Although most of a eukaryotic cell's DNA is contained in the cell nucleus, the mitochondrion has its own genome ("mitogenome") that is substantially similar to bacterial genomes.
[1] https://en.wikipedia.org/wiki/Mitochondrion
ale42|6mon ago
There's a specific page on Wikipedia about Mitochondrial DNA [1], where it is clearly said that:
In the cells of extant organisms, the vast majority of the proteins in the
mitochondria (numbering approximately 1500 different types in mammals) are
coded by nuclear DNA, but the genes for some, if not most, of them are
thought to be of bacterial origin, having been transferred to the eukaryotic
nucleus during evolution. (citing [2])
725686|6mon ago
They were, originally. Over the eons, they have lost many of their original genes. Source: Nick Lanes fantastic books, specially Power, Sex, Suicide
thinkling|6mon ago
Saw another recommendation for that book in this discussion and will be reading it. Thanks.
bonzini|6mon ago
See below on Wikipedia: "Most proteins necessary for mitochondrial function are encoded by genes in the cell nucleus and the corresponding proteins are imported into the mitochondrion. The exact number of genes encoded by the nucleus and the mitochondrial genome differs between species."
melagonster|6mon ago
yes, Human mitochondria only generate less than 20 types of protein; all other things they need are from cytoplasm.
amy-petrik-214|6mon ago
Yea I would def. not call mitochondria "alive" since they are so deeply integrated with the rest of the cell & vice versa.
mito is like <100k bp vs 3000000k bp in human genome (bp = base pair = "character" in a string)
principle derives from the concept of "the selfish gene" or "the red queen" these famous books on the topic. Arms races between X and Y chromosome. Arms race between nucleus and mitochondria, and so on.
or put it this way. why do all animals have sex? because it generates gene sequences that confer fitness more efficiently than self-replication (which is the typical repro method of unix programmers)... .. generates such gene sequences for NUCLEAR DNA that is, mito DNA comes from mom only (the red queen.. .. "mitochondrial eve" ... "y chromosomal adam".. etc). and thus the mito is fundamentally unable to wield the power of evolution, completely evolutionarily outclassed by those nuclear chromosomes. thus exporting all its genes to the nucleus, conferring advantage to all such progeny with their superior power supply
Tor3|6mon ago
I don't understand this definition of "alive". Isn't every cell in my body alive? There are definitely differences between an alive cell and a dead one.
FollowingTheDao|6mon ago
> There are definitely differences between an alive cell and a dead one.
Energy flow is the difference. but then everything has an energy flow. Losing and gaining electrons. So it is possible that literally everything is alive, don’t you think? Maybe the problem is is that we’re trying to make a definition where none ultimately really exists.
kylebenzle|6mon ago
OP above you is correct. Maybe you are thinking about it wrong?
dekhn|6mon ago
what about obligate intracellular parasites like mycoplasma? They are awfully close to mitochondria but we think of them as alive. They've lost many of their genes and can't survive without the host. Looking at those, you could almost see a path from an obligate intraceullular parasite to an organelle derived from a phagocytosed prokaryote.
colechristensen|6mon ago
But that’s exactly what they are, former endoparasites which gradually lost their independence and became more specialist in their function.
Defining an arbitrary line and then attaching labels does not really add to understanding.
d0mine|6mon ago
But it does. How many grains of send form a heap? How many atoms form a fluid? Is it something a particle or a wave? The line can be drawn depending on specific problem, on how useful a heap/fluid/particle/wave model for this specific application.
A label (abstraction) allows us to bring corresponding tools that were developed for it. If you can count trees then the same math can be useful to count people.
meneton|6mon ago
Arguing about where you draw the line doesn't advance anything, it just muddies the water. We have robust definition of what is and isn't alive built by consensus. Mitochondria fall into the 'not alive' category by our definition. Presenting decades old scientific views as evidence that this categorisation is wrong doesn't add anything. This article has had far more exposure than some really groundbreaking science and it adds nothing.
d0mine|6mon ago
My point is more general: there may be multiple useful descriptions of “reality” depending on context. It is almost _trivially_ (tautologically) true. Ask two different programmers to implement something and look at what abstractions they create depending on unrelated non-functional requirements. Here’s specific example: imagine you are writing “what-if” type of article about a table: if you are interested in whether it holds your weight then you might talk in terms of tension, compression, mechanical forces. If you are interested in whether you can hide behind it from x-rays then terms such as radiolucent, atomic composition might be useful.
I have no idea in what context “mitochondria are alive” notion might be useful (but it doesn’t mean there is none).
astrobe_|6mon ago
This called symbiosis. When a parasite such as a virus, a bacteria, a fungus, a plant, an insect and its host find a win-win "agreement".
ElFitz|6mon ago
This "aliveness" debate reminds me of the "11.000 years old dog". Basically a tumour that has been spreading from one dog to another for thousands of years.
https://www.cam.ac.uk/research/news/11000-year-old-living-do...
sroussey|6mon ago
Mitochondria are weird. Look at 3-parent baby (human).
lo_zamoyski|6mon ago
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
Your heart cannot exist independently of you as a heart. It is only a heart in name, as it does not function as a heart. Its identity as a heart depends on its ability to function as a heart within some organism. The same can be said for any part or organ. A severed hand is a hand in name only. A corpse is not a body, as it no longer functions as one.
A transplanted heart becomes a heart once more. A reattached hand becomes a hand once more. If you think this is weird, then you haven't done your metaphysical homework. Why should it be weird? It could only be weird if you have made certain (unexamined) metaphysical presuppositions. The structure of a heart removed from an organism persists long enough that it can become reintegrated into an organism such that it functions once again as a heart.
But also note that the matter composing a heart itself isn't fixed. About 1% of heart cells are replaced per year in the young. So if function and structure can survive transient material change, and the matter that makes up a heart can assume and lose and reassume its identity as part of a heart, then why can't a heart lose its identity as a heart when removed, and regain its after it is implanted back in?
type0|6mon ago
> There have been many such endosymbiotic events in the history of life - there are subfields of evolutionary biology that study these processes.
Exactly, if mitochondria is alive then so is chloroplasts and who knows what else. The line needs to be drawn somewhere, also life and death isn't as clear-cut as many used to believe
rgbswan|6mon ago
You might find this interesting:
"Clinical potential of sensory neurites in the heart and their role in decision-making"
xphos|6mon ago
I think questions like this make science fun for the uninitiated because it represents both the uncertainty and the intense investigation and evidence discovery process involved in tearing hazy things and recovering concrete truths in the process
macawfish|6mon ago
It's wild to me that today's popular biologists like Michael Levin don't give Lynn Margulis credit in every single podcast/interview.
freetime2|6mon ago
Can you elaborate on this comment? What should popular biologists like Michael Levin be saying on every podcast/interview and why? Serious question from someone who is familiar with Lynn Margulis but not Michael Levin.
monktastic1|6mon ago
Are you not "totally dependent" on the air you breathe, the water you drink, the sunlight that gets turned into your food, ...?
softfalcon|6mon ago
I don’t disagree with your take. The concept of the semantics of “what is alive?” has been going on for a long while now.
Have you considered that this is a more formal version of a Bill Nye science explainer, but for adults?
The reason I say this is that while unintended (I think) your post has a, “of course they’re alive, we’ve known this forever” vibe, which can inadvertently come across as condescending.
I don’t mean to pick on you, we’re all guilty of such speak when we deem concepts to be obvious or well known.
Your post reminds me of the “1 in 10,000” XKCD comic:
Again, I don’t disagree that your knowledge of history and science is correct. Am just curious why you wrote your explainer in the way you did.
liyamchitayat|6mon ago
Hi!
I agree with you, which is why I wrote this- but if you google "are mitochondria alive" gemini says it isn't. And yes, the cells in your heart have an effective and potenitial niche!
We seem to have many tools to engineer viruses, but few to engineer mitochondria- perhaps considering them as alive could change that!
satvikpendem|6mon ago
I am not sure you should be relying on an LLM as any indication of anything...
More seriously, considering something as being alive in order to engineer them better does not necessarily change the fact of them actually being alive or not, in my opinion.
dekhn|6mon ago
If LLMs work the way I understand them to, they are trained on large corpora which contain a statistical preponderance of statements which are consistent with the current scientific mainstream, so it may not be completely crazy to try doing this; you'd get the scientific mainstream explanation, and possibly a few alternative hypotheses if they had enough literature support.
govg|6mon ago
Why would it be consistent with the scientific mainstream? Unless there's evidence that scientific reports and material are specifically up-weighted during training and prioritised somehow, whatever an LLM says will be only consistent with its training material, which could have any proportion of fake articles, Reddit posts, Quora responses, encyclopedia pages and joke blogs
opello|6mon ago
> which are consistent with the current scientific mainstream
This seems to require a high amount of curation of training inputs, but I haven't done real digging into it, just going off the more casual "all of stackoverflow" or "all of reddit" type comments frequently thrown around. But if there is such a curation I'd agree, I just don't think there is that curation.
satvikpendem|6mon ago
You don't know what the training data is and what each category's weights are, so how can you assume that?
dekhn|6mon ago
Most use common crawl, and most seem to upweight the scientific publication part of it (from what I gather speaking to folks who train LLM models).
Jerrrry|6mon ago
You are literally saying this novel thing is wrong because this thing that can't say novel things says the thing that's not novel is not novel.
JumpCrisscross|6mon ago
> if you google "are mitochondria alive" gemini says it isn't
And my grandmother is a bicycle.
DonHopkins|6mon ago
Therefore, a man needs God like a fish needs your grandmother!
mock-possum|6mon ago
Still one of my favorite idioms
tim333|6mon ago
I just tried that and it said:
>Yes, mitochondria are alive, though they are not considered "living" in the same way as a cell because they can't function independently...
Maybe it's learning!
jpk|6mon ago
Or maybe the temperature is set too high! Probably don't start with a single LLM response as the basis for your understanding of scientific consensus.
UniverseHacker|6mon ago
Eukaryotes generally can’t survive without mitochondria either. It seems silly to discuss if different subsystems in a living organism are independently “alive.” It’s a bit like arguing if just the wings or just the engine of an airplane are flying machines.
meneton|6mon ago
You are completely right that we should be thinking far more creatively about manipulating mitochondria. There are a lot of diseases (including Covid) that have mitochondrial aspects. I just don't think calling them alive helps, other than to get you some decent exposure on HN :)
dragandj|6mon ago
"Gemini" says? So what?
tim333|6mon ago
It shows there are misconceptions out there, if only in LLMs.