I wonder what mitochondria dream about. Do they have elections? Politics? Their own understanding of the universe, that somehow ends on the skin surface?
As a layman I'm kind of baffled by the enduring pop-sci interest in mitochondria.
To me the far more interesting organelle is the ribosome. This elegant self-replicating machine that is highly conserved across lifeforms is fascinating and much closer to the origin of life than mitochondria.
How did ribosomes evolve? Are the ribosomes that we see in modern organisms the first design that did evolve? Why are they highly conserved?
That's a debatable statement and it doesn't explain the public appeal of mitochondria over ribosomes that predates recent research on the relationship between mitochondria and aging.
But there is a connection between the X and Y in this case.
One is a subset of the other. We're talking about the same thing man, I'm just making the point that I feel that there should be greater emphasis on the subset.
Look at the top thread in this post, people are doing a very similar thing.
I truly think that the pop-sci interest in mitochondria stems from the nickname and for no other reason and to me that's a very interesting thing.
It's a little confusing to look into, because there's a bunch of separate theories about the nature of aging that all involve mitochondria in some way. You will find news articles saying that the mitochondrial theory of aging was discredited because of some study done, but when you look into it, it turns out that what was shown was that some specific variant of the theory was insufficient for accounting for all forms of aging, which is not the same thing. Each mitochondrial theory of aging is a theory about one pathway by which mitochondrial function or dysfunction results in aging damage, the reality is that many or all of these theories are true and aging is the aggregation of damage from all of them, and more pathways we have yet to discover.
Generally speaking, the vast majority of aging damage comes, directly or indirectly, from the accumulating damage from healthy operation of mitochondria over long periods of time, or the accumulation of cells with unhealthy mitochondria that produce damage more rapidly. The ELI5 is that mitochondria produce free radicals, free radicals chemically alter basically anything they touch, and aging is simply the slow accumulation of intercellular and intracellular damage, and if you follow the history of these molecules back to when they diverged from being in a healthy state, it is almost always the result of oxidative damage (e.g. free radicals of the sort produced by mitochondria).
Another ELI5 way of looking at it: you may not know this, but mitochondria only live a couple of days. They are constantly being refreshed in your cells because of the severe oxidative stress they undergo. They also sometimes break or leak, letting those reactive oxygen species into the cell and causing damage. Aging is the accumulation of this damage.
But I said aging was "downstream of" mitochondrial dysfunction. That's because not all aspects of aging is due to reactive oxygen species leaking out like I seemed to claim above. That's just one example. There are cells in your body that have lost all mitochondria, often due to a freak genetic mutation in the mitochondrial DNA of that cell. Surprisingly these cells don't die, but rather switch into a mode of operation where they slow down and live off energy extracted from the intercellular medium and converted into ATP by various molecular systems embedded in the cell membrane. These processes, as it turns out, free radicals out of the cell during operation, spewing reactive species into the body. This ends up being responsible for hardening tissue, lack of energy, and many other symptoms of aging. But the root cause? The mitochondria stopped working in that cell, so still a mitochondrial issue.
Or, the aging of heart cells and the hardening of arteries is largely due to the collection of dysfunctional lysosomes that are full of garbage they are unable to break down. These clutter cells, harm their efficiency, and eventually have enough collective effect as to make the tissue as a whole less viable. Leading to heart attacks and other cardiovascular disease, which is the leading cause of age-related death alongside cancer. Want to guess what these defective lysosomes are full of? Mostly undigested mitochondria, specifically the highly damaged structures of mitochondria that suffered too much oxidative damage from long operation.
Oh, and what about cancer? Well cancer needs A LOT of energy to keep replicating, and so it should be no surprise that many of the mutations among common cancers have to do with genes in the nucleus affecting mitochondrial function, or the various signaling pathways between the nucleus and the mitochondria of the cell. This article covers some of the ways that cancer uses mitochondria: dist-epoch↗
Todays ribosomes are not alive by any definition.
But it's possbile they are descendants of some self-replicating self-catalyzed RNA chain (RNA world)
Nah [1]. They do single task. They just read RNA, pick amino acids [1] and make proteins. If a cell were your house, it's like a 3D printer.
Mitochondria are much bigger, they have their own DNA, they reproduce, have a lot of internal structure, they do all the task of a normal cell. If a cell were your house, it's like having a bunch of squirrels trained to wind the clocks in exchange for peanuts.
[1] The definition of alive is complicated, so I prefer a "Nah" instead of a super hard "No".
[2] There are some details I'm hiding, like mRNA, tRNA and even rRNA.
It's funny that this phrase has had such staying strength, while the key word in it, "powerhouse," has fallen out of fashion. The more modern American English way to phrase it would be "the power plant of the cell."
Distinction: I am a millennial, and actually had to go look up just now what a "powerhouse" is. I am familiar with the term in its metaphorical sense, but was heretofore unacquainted with the literal definition. "Power plant" or "power station" would, yes, be more immediately understood by my generation. The phrase "Mitochondria is the powerhouse of the cell" would read to modern children like saying "The mitochondrion is the rock star of the cell."
These things do happen. I was in my 30s before I learned what the "firewall" of a car was...
Anecdotally, I feel like I've heard "powerhouse" used somewhat regularly when describing impressive people, i.e.: "Such-and-such is an absolute powerhouse on the field", or "That person is so productive, they're a powerhouse".
So maybe the original usage has been subsumed by "power plant", but I think the word has alternative meanings which persist.
That's an interesting thought, I haven't picked up on it but you're right. Most of my associations with powerhouse are from trails or ares that used to have powerhouses and now have empty buildings, ruins or traces left over. I do think about powerhouses in the context of dams but that is likely leftover from an earlier time.
Powerhouse is a common way to describe an athlete, a high performance engine, or a very strong stock buy -- it has just moved away from the infrastructural uses.
this is the first ive heard of mitochondria replicating separately and distinctly from the host cell, how fascinating!
Are we saying that mitochondria have their own life cycle inside of a cell? living/dying/replicating in the span of the "life" of a single host cell? When a host cell reproduces, how does the mitochondria get produced in the new cell to get things started?
The two halves of the divided cells will usually both have mitochondria. Not always, though; sometimes cell division leaves one cell without any mitochrondria. That usually results in a non-viable cell, but sometimes the cell can survive with limited capacity. Some species that used to have mitochondria have apparently been through this process and have evolved to survive in their absence; Giardia duodenalis for example.
I think the idea here is that mitochondria developed independent of cells and later lived exclusively inside of them. In other words, they reproduced without cells. I am not sure, please correct me if I am wrong.
You're not wrong. But over the enormous amount of time since, the "duplicate" organelles and systems needed for independent living were steadily carved out of mitochondria. While they do have their own DNA and replication process, the DNA is basically limited to specific things they need to perform their energy-generation functions and the replication happens when triggered by host cell replication.
It's a bit like if you took the heart from an animal and transplanted it into a human: is it meaningful to call it independently alive? Maybe, it depends what question you're trying to ask.
I don't know of any definition of "alive" that can survive application of a reductive understanding of biology that doesn't either count viruses as being "alive," or decide that nothing is alive.
The uncertainty, I understood, was whether to classify them as distinct organisms the way we classify other species, as they are intrinsically parasitic for their replicative capability.
Outside of a host cell viruses do not fit any of the definitions of life:
- they do not seek or consume sources of nutrients or energy
- they do not have a metabolism
- they do not grow
In fact the only place they fit the definition is reproduction, and that is only through the machinery they commandeer from the cells they infect.
To me viruses clearly do not fit the definition of life. But fire... that is hard to exclude from the definition without some mental contortions. I am not advocating that fire is alive for any useful reason, but it is hard to exclude from the definition.
I am terrible at biology but I will try. The idea is that mitochondria is not a component of a living organism, but an organism that once lived independently of the cell.
"If we think of mitochondria as non-living organelles..."
mitochondria were thought to just be a component of the cell. But they have their own DNA separate from that in the cell's nucleus. They replicate on their own like bacteria.
That's a discussion about word semantics that has no relation to biology. Biologists have been occupied with it for centuries, just like computer people have lost time on "what's intelligence?", but neither one is relevant for either field.
> Are they bacteria?
Once upon a time, their ancestors were. I do not know exactly where biologists trace the line, but this is also about word semantics. It's just a case of it that helps people communicate better, so there is a line, I just don't know what it is.
What do you mean by "alive?" Because of course they are alive, regardless of whether you consider them bacteria or not. There is a strange definition of "alive" that is being used by you and the author article that I'm not understanding.
If a mitochondria is not "alive," then is it dead? Even if it is taking part in an active, living cell?
Organelles are alive too. All active biological systems are alive.
Mitochondria have for many generations now been known to have their own DNA and replicate on their own. So I’m not sure what new distinction is being drawn?
I _think_ what they mean is it's not typically listed as a "life form" in its own right, i.e., there's no Domain under which one would classify Mitochondria - maybe just calling them bacteria would capture the article's intent?
So, the modification would be that we are living in symbiosis with mitochondrial bacteria, similar to how we live in symbiosis with our gut bacteria, rather than them being classified as "organelles" of eukaryote cells.
That's more a flaw of classification systems though. Because even if they comprise a distinct life form does not mean they need to have a unique species. Consider lichen, which comprise two (or more!) separate "species" which becomes a meaningless distinction when they cannot survive on their own, or even if they could, not in a form recognizable in any wayas they were when they were a part of the symbiotic system
I mean at that point what do we consider multicellular organisms? Did you see what was going on with those frog skin cells and "xenobots"? Also, our gut bacteria kinda makes us a symbiote at a larger scale.
As others note, it is classified in the tree of life. We know approximately what kind of bacteria it evolved from, and mitochondria themselves constitute their own divergent branch of the tree of life (there are many longitudinal studies of mitochondria across species).
But if you wanted classify them based on functionality rather than evolutionary history, I'd say they're more like viruses. They have only a handful of genes themselves, and exploits the nucleus' genetic material for all the other proteins it needs to function.
Depends on your definition of organelle (whether you limit it to plastids/mitochondria, both of which were derived from external independent living cells, or use a more expansive definition that includes more cell compartments that weren't derived from independent living cells).
General acceptance of the endosymbiont theory is a relatively recent (much less than 50 years) phenomenon.
> If one considers bacteria as living entities — and all biologists seem to — then it is impossible to explain why mitochondria are not.
There seems to be a strange, half-hubris, half-pride vein that runs through Humanity that would see us as lesser for being hosts to benevolent bacteria, despite us very obviously being unable to survive without benevolent bacteria.
We didn't evolve to understand "self", and indeed most animals do not. There was no evolutionary pressure to do so. We're having to discover it piece by piece.
We aren't driven solely by evolutionary pressure. We can (and have) developed cultures that can easily accept that humans are "just" part of a larger system, even having a unique role, without having to be superior. Our culture isn't like that, of course. We are obviously doing a good job of being "in charge" of the planet and definitely not charging headfirst into a mass extinction event with our collective eyes closed.
Most of the Japanese games/media foreshadow/hint you about actual or potential facts written in papers but not understandable to teenagers until theẏ grow up.
I don't know why this is being downvoted. It's quite apropos for being a piece of fiction toying with this very concept.
It is a videogame based on/continuing a cheesy scifi novel that played with the concept of mitochondria being alive (also sentient). Sure it's not quite scientifically sound, but it still explains the concept with enough actual facts (very easy to distinguish from the fictional ones), and the ludicrous nature of it all makes it so you won't *ever* forget that mitochondria are in fact a part of the cell and their normal function is being involved in energy production.
I can warrant 90% of people who ever thought about the mitochondrion's existence and function (beyond basic school formation) that aren't working or studying in related fields are just people who played this game. I can bet there's a non-zero amount of scientists that got into this stuff because they played the game as kids or teens.
Any time I read a mitochondria post like this, I strongly recommend that others who find the topic interesting check out Power, Sex, and Suicide by Nick Lane.
Absolutely loved TVQ. The insight about mitochondrial DNA inheritance being exclusively from the mother, thus motivating female fingerprinting of male nucleic DNA for gamete viability (via courtship rituals, pheromones, plumage, etc)...
a lot of focus on the definition of "alive" in the comments, but i think that the weight of this rests on it being a step toward confirming the endosymbiotic relationship theory which states that mitochondria were potentially part of another eukaryotic cells carrying what would become mitogchodria were engulfed by another cell. this affected cellular development by outsourcing energy production for the cell itself. a lot of times the results seem "self-evident" but you still have to find evidence to support or reject a theory and this seems like a step in that direction.
I still think about the fact that we're this close to proving the protocell theory, proving that we can create life from no life. Last time I read about it was 2021, and I'm really curious when the day arises we succeed
They are obviously alive, but also we are obviously a colony organism. The various bacteria we transmit from mother to child, the mitochondria inherent to our cells, all of this stuff is just part of a self-similarity of life from top to bottom. With sufficient zoom-out, we need not treat individuals (or pairs) as the only unit of life replication.
That seems to be an overly reductive view on the value of knowledge.
What practical purpose does studying ancient civilizations have? Why do we send expensive telescopes into space to study faraway galaxies and try to uncover mysteries of the big bang? When can we expect the results from number theory to lower the price of gas at the pump?
Knowing that mitochondria have their own DNA is knowledge. Knowing that they reproduce independently of their home cell is knowledge. Learning whether they evolved from a separate viable organism would be knowledge. Learning whether we can make them viable, or breed them separately, and use them in therapies -- all knowledge.
Whether they are "alive" or not is just the definition of a word.
Much of science is about defining words in ways that match the underlying general structure of the system being studied.
A subset of scientists want to come up with an operational definition of "What is life", which may or may not include things like viruses and mitochondria. As you say, it's mostly definitional, but by defining this, we can potentially make our understanding match up with the latent reality.
It doesn't seem the article addresses this, but I'd ask these questions: "would it be possible that mitochondria's evolutional interest and the organism's interest are not aligned?" "how many independent DNA can an organism possess?" "why mitochondria do not elicit immune reactions? Or can they?"
2) By "organism" I assume you mean "cell" since humans have several thousand different species with their own DNA living on or inside the body at any given moment. We can speak of animal cells, which have two (species and mitochondria) - and plant cells, which have three (species, mitochondria, and chloroplasts). If there can be one two or three, I don't see why there couldn't be even more.
3) Mitochondria are usually sequestered within the cell, which limits their exposure to immune cells. The immune system primarily targets pathogens that are outside the host cells. In fact, some pathogens can exploit mitochondrial pathways to evade immune detection - the most famous of which is HIV.
> Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them.
Once you accept mitochondria as alive, you might be motivated to explore its "potential" niche, as described by the author. The example of implanting cross-species mitochondria in human cells (e.g. from a gorilla) might lead to novel therapies.
It's about breaking outside the box of mitochondria having to live inside specific environments.
So the theory is that if we don't accept them as alive, then we can't experiment with implanting cross-species mitochondria in human cells? Why not? What stops us from doing this?
This is a fair point. I can see the excitement around recognizing that mitochondria is alive to motivate exploring its other functions. But I think you're right someone might be interested in that exploration regardless of whether it's considered alive.
Edit: to your point, there are plenty of scientists interested in studying viruses and much debate about whether or not they are alive. Ultimately it probably doesn't matter.
I do think when you consider mitochondria to be alive, it broadens the scope of your thinking because you start considering each characteristic of life in relation to mitochondria. You might not be motivated to do that without thinking in those terms.
I recognize that you might be motivated to explore removing and implanting mitochondria regardless of whether you consider it to be alive (as you might think about implanting an organ from another source).
I think the main point the author is making is to not fall prey to reductive thinking about mitochondria's potential and less about the question of "aliveness". We were all taught about mitochondria producing ATP, but it sounds like it serves many other functions and there's a lot more to explore about its potential in synthetic biology and therapeutics.
It matters for a number of reasons, but the main reason in terms of pure biology is that it was not originally recognized that cells could absorb other cells and utilize them for the absorbed cell's natural function.
This meant, importantly, that we learned cells did not always need to evolve a functionality from scratch, but could acquire it through phagocytosis.
It's also a useful tool for studying evolution for many reasons.
Whether or not mitochondria were once viable independent organisms that were absorbed by early eukaryotes does not depend on whether we call their modern descendants "living" or not. If we determine that they did, then we still don't have to call them alive -- certainly things like mitosomes exist and are suspected to have either evolved from mitochondria or evolved after amitochondrial division, but do not have DNA and do not reproduce independently but fulfil similar functions.
We know they have DNA, we know they reproduce independently of the host cell, we know to a degree why they tend to move to both sides on cell division. We know lots of stuff about them and we can always learn lots more. Whether they are "alive" or not has absolutely no bearing on that, other than to naval-gaze.
I think we're in agreement then -- this article is not about "did mitochondria evolve from absorbed viable organisms as opposed to evolving directly", which is an interesting question that impacts our understanding of evolution in microbiology. The article is about whether "Microchondria Are Alive" which is a useless naval-gaze.
For example I could easily see a scientist asking the question, "if mitochrondira are not alive, at which point did the phagocytosis of the initial prokaryotic cell lead to the mitochondria not being alive?" "What components were lost in the cell that lead to the loss of life?" I agree these aren't particularly useful, and are ultimately definitional, but definitions matter a lot in science, especially when paradigms change.
This is a much more interesting question, and this is what I mean by an operational definition of life. In your first question, "alive" can have useful operational definitions -- whether it is viable outside of a cell, whether it has or had its own immune system and structure, how it survived without the organelles that other full-fledged cells seem to have but mitochondria lack, etc.
The question in the abstract is not really useful except to answer trick questions in bar trivia.
I was equally dismissive of the actual importance of philosophizing whether mitochondrias are alive or not, but this paragraph made me change my mind.
> It seems Mitochondria are not bound to their host cell; they can travel between different cells. Although different species carry distinct mitochondria, experiments show that mitochondria from one species can be transferred to another.
> In 1997, scientists isolated mitochondria from chimpanzees and gorillas and showed that they are naturally internalized and integrated into human cells. Notably, the addition of external mitochondria even showed therapeutic benefits in heart failure and spinal cord injury. Thus, the potential niche that mitochondria can live in is greater than their effective niche.
So it seems like they are more symbiote than organelle, that's amazing.
The question itself if just semantics. But considering our mitochondria as evolving populations subject to selective pressure and genetic drift is really important to understanding their role in our health, down to basic questions like "Why is exercise healthy?"
>Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them.
This assertion is made but not supported. I don't think I understand the importance of this distinction, assuming that everyone already agrees about the evolutionary and mechanical facts about mitochondria, but as far as I can tell, no one disagrees that mitochondria were originally free living cells, or that they have their own DNA, or any of the other relevant facts about their origins or how they work in the cell. It's merely an argument about what it means to be alive. Which is philosophically interesting, but practically unimportant for the practice of biology.
This seems like a purely semantic debate with no broader importance.
More than 95% of all proteins located in the mitochondrial compartments are encoded by the nuclear DNA, synthesized in cytoplasmic ribosomes and imported into mitochondria. These include factors that regulate mitochondrial DNA (mtDNA) gene expression such as mtDNA and RNA polymerases, mitochondrial transcription factors, RNA processing and modifying enzymes, transcription termination factors, mitochondrial ribosomal proteins, aminoacyl-tRNA synthetases, and translation factors (1, 2).
It's clear that a mitrochondrial element can't live for long without the presence of the host cells, so, like a virus, it doesn't meet all the requirements to be considered fully living.
The fact that every child on the planet is religiously taught that the mitochondria is the powerhouse of the cell is all the evidence I need that we're upholding a primordial contractual agreement and these are the conditions to which we are beholden.
Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool.
I actually never heard the phrase until I got online and saw the meme!
My biology classes did have us gene editing bacteria to chance its color. That was fun!
> The only one that comes close is Athlete's Foot, which makes the victim sound cool.
The best cure for athletes foot is a 30 minute soak in diluted bleach. Get a wash basin, fill it with warm water, and add enough bleach so that it tingles a little bit.
Do this every other day 3 times, e.g. Monday, Wednesday, Friday. Problem solved.
Make sure to clean out the shoes as well, ideally not wearing any infected shoes for a few days at least, and soak the insides with Lysol a few times to prevent reinfection.
Depends on how diluted the bleach is. Also 30 minutes may be more than necessary, but it's what I've always done for athlete's foot. For other random crap that's tries to grow on my skin I'll dilute some bleach on a paper towel and let that sit on whatever is trying to eat me.
The basis of this technique is that you have skin to spare, and your skin regrows.
Nitpick: except red blood cells. White cells very much do have mitochondria.
RBC's don't need them because they are incredibly low-metabolism. It's energetically cheaper for the organism just to make them, let them go for a few months, and then recycle the components.
As far as I’m aware we’ve never worshipped mitochondria. And unless you want to count eating which is technically true but not philosophically so, we don’t sacrifice plants or animals to mitochondria.
The explanation doesn't get much better at higher levels. You have the Krebs cycle which biology people religiously memorize but it doesn't really explain much either. The actual interesting part is usually handwaved away as "magical enzyme/protein" catalysis. Understanding how the mitochondrial proteins/enzyme catalysts function would usually require a graduate degree, and maybe a background in biochemistry and biophysics.
If you haven't, I suggest you look up an on how ATP Synthase uses the proton gradient to create ATP. It's quite amazing. It's literally a little nano-machine.
>"Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool."
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.
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?
> 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.
> 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.
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.
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?!
>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.
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 !!!!
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?
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.
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....
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
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.
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.
> 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).
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"
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.
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.
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.
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!
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.
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.
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.
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.
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.
"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."
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?
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.
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.
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.
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.
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.
> 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.
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.)
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.
> 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.
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.
> 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.
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.
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.
>I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later,
Two convergent intuitions as to why this is true, but for the wrong reasons:
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'.
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.
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.
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.
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.
--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.
>>> ...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....
How would I know my reader would had misconstrued my "unclear" (read: perfectly grammatically specific) intentions a priori?
Did we both edit our posts....to improve accuracy, increase resiliency, and to compete ideas?
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?
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)
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.
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.
People aren't intimated by people that cannot replace them, they are by people that can.
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.
But somewhere between a middle school drop out and a super-intelligence and 5-layers QED, I think my posit has merit.
Free to continue discussion; but the under the Ego lies the Id, and I'm not well versed in that science yet, still approximating.
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.
>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.
yes, this is why evolutionary theory is the softest of hard sciences and the hardest of soft sciences.
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.
> 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.
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.
>reserving them for cooperation or something like slavery happens, but it's a rare strategy specific to intelligent animals
Exactly, GP thinks this is a higher order behavior.
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
Beating a rival and taking their energy is awesome!
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
> 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.
Talking about what is considered "alive" is an interesting exercise, and shows just how fuzzy those boundaries can be sometimes. But I really don't see how this has any practical impact on how we study mitochondria.
> If we think of mitochondria as non-living organelles, how will we ever harness their full potential?
Whenever anyone uses the "harnessing [its] full potential" cliché, my bullshit alarm starts buzzing. I don't think this article is bullshit, but...we can "harness" as much "potential" as mitochondria have whether we consider them alive or not.
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To me the far more interesting organelle is the ribosome. This elegant self-replicating machine that is highly conserved across lifeforms is fascinating and much closer to the origin of life than mitochondria.
How did ribosomes evolve? Are the ribosomes that we see in modern organisms the first design that did evolve? Why are they highly conserved?
Are ribosomes alive as well?
I think it's the catchy nickname "powerhouse of the cell."
Ribosomes don't have a catch nickname so they get a lot less content produced about them.
If I was a highschool biology teacher I'd probably call them "The assembly line of life." That would stick in people's minds I bet.
My intention in asking the question isn't to create animosity. I'm just curious why the thing that I've observed is a thing.
One is a subset of the other. We're talking about the same thing man, I'm just making the point that I feel that there should be greater emphasis on the subset.
Look at the top thread in this post, people are doing a very similar thing.
I truly think that the pop-sci interest in mitochondria stems from the nickname and for no other reason and to me that's a very interesting thing.
It's a little confusing to look into, because there's a bunch of separate theories about the nature of aging that all involve mitochondria in some way. You will find news articles saying that the mitochondrial theory of aging was discredited because of some study done, but when you look into it, it turns out that what was shown was that some specific variant of the theory was insufficient for accounting for all forms of aging, which is not the same thing. Each mitochondrial theory of aging is a theory about one pathway by which mitochondrial function or dysfunction results in aging damage, the reality is that many or all of these theories are true and aging is the aggregation of damage from all of them, and more pathways we have yet to discover.
Generally speaking, the vast majority of aging damage comes, directly or indirectly, from the accumulating damage from healthy operation of mitochondria over long periods of time, or the accumulation of cells with unhealthy mitochondria that produce damage more rapidly. The ELI5 is that mitochondria produce free radicals, free radicals chemically alter basically anything they touch, and aging is simply the slow accumulation of intercellular and intracellular damage, and if you follow the history of these molecules back to when they diverged from being in a healthy state, it is almost always the result of oxidative damage (e.g. free radicals of the sort produced by mitochondria).
Another ELI5 way of looking at it: you may not know this, but mitochondria only live a couple of days. They are constantly being refreshed in your cells because of the severe oxidative stress they undergo. They also sometimes break or leak, letting those reactive oxygen species into the cell and causing damage. Aging is the accumulation of this damage.
But I said aging was "downstream of" mitochondrial dysfunction. That's because not all aspects of aging is due to reactive oxygen species leaking out like I seemed to claim above. That's just one example. There are cells in your body that have lost all mitochondria, often due to a freak genetic mutation in the mitochondrial DNA of that cell. Surprisingly these cells don't die, but rather switch into a mode of operation where they slow down and live off energy extracted from the intercellular medium and converted into ATP by various molecular systems embedded in the cell membrane. These processes, as it turns out, free radicals out of the cell during operation, spewing reactive species into the body. This ends up being responsible for hardening tissue, lack of energy, and many other symptoms of aging. But the root cause? The mitochondria stopped working in that cell, so still a mitochondrial issue.
Or, the aging of heart cells and the hardening of arteries is largely due to the collection of dysfunctional lysosomes that are full of garbage they are unable to break down. These clutter cells, harm their efficiency, and eventually have enough collective effect as to make the tissue as a whole less viable. Leading to heart attacks and other cardiovascular disease, which is the leading cause of age-related death alongside cancer. Want to guess what these defective lysosomes are full of? Mostly undigested mitochondria, specifically the highly damaged structures of mitochondria that suffered too much oxidative damage from long operation.
Oh, and what about cancer? Well cancer needs A LOT of energy to keep replicating, and so it should be no surprise that many of the mutations among common cancers have to do with genes in the nucleus affecting mitochondrial function, or the various signaling pathways between the nucleus and the mitochondria of the cell. This article covers some of the ways that cancer uses mitochondria: dist-epoch ↗ Todays ribosomes are not alive by any definition. jamiek88 ↗ They are both very interesting. I don’t think there’s necessarily interest in one are the expense of another? francisofascii ↗ Mitochondrial health is considered a strong proxy for overall health. gus_massa ↗ Ribosomes are much smaller than mitochondria. Moreover, mitochondria have a lot of ribosomes inside that they use to make their own proteins. https://en.wikipedia.org/wiki/Mitochondrial_ribosome
But it's possbile they are descendants of some self-replicating self-catalyzed RNA chain (RNA world)
> Are ribosomes alive as well?
Nah [1]. They do single task. They just read RNA, pick amino acids [1] and make proteins. If a cell were your house, it's like a 3D printer.
Mitochondria are much bigger, they have their own DNA, they reproduce, have a lot of internal structure, they do all the task of a normal cell. If a cell were your house, it's like having a bunch of squirrels trained to wind the clocks in exchange for peanuts.
[1] The definition of alive is complicated, so I prefer a "Nah" instead of a super hard "No".
[2] There are some details I'm hiding, like mRNA, tRNA and even rRNA.
These things do happen. I was in my 30s before I learned what the "firewall" of a car was...
So maybe the original usage has been subsumed by "power plant", but I think the word has alternative meanings which persist.
Powerhouse is a common way to describe an athlete, a high performance engine, or a very strong stock buy -- it has just moved away from the infrastructural uses.
Are we saying that mitochondria have their own life cycle inside of a cell? living/dying/replicating in the span of the "life" of a single host cell? When a host cell reproduces, how does the mitochondria get produced in the new cell to get things started?
Cant wait to research this later.
Each half of the cell keeps the mitocondria that were living inside it.
But I have never been a fan of that argument either, both seem alive to me.
It's a bit like if you took the heart from an animal and transplanted it into a human: is it meaningful to call it independently alive? Maybe, it depends what question you're trying to ask.
The uncertainty, I understood, was whether to classify them as distinct organisms the way we classify other species, as they are intrinsically parasitic for their replicative capability.
In fact the only place they fit the definition is reproduction, and that is only through the machinery they commandeer from the cells they infect.
To me viruses clearly do not fit the definition of life. But fire... that is hard to exclude from the definition without some mental contortions. I am not advocating that fire is alive for any useful reason, but it is hard to exclude from the definition.
mitochondria were thought to just be a component of the cell. But they have their own DNA separate from that in the cell's nucleus. They replicate on their own like bacteria.
... hundreds of years ago, for a short time after they were discovered.
We know that they behave like bacteria for almost as long as we know that they exist.
That's a discussion about word semantics that has no relation to biology. Biologists have been occupied with it for centuries, just like computer people have lost time on "what's intelligence?", but neither one is relevant for either field.
> Are they bacteria?
Once upon a time, their ancestors were. I do not know exactly where biologists trace the line, but this is also about word semantics. It's just a case of it that helps people communicate better, so there is a line, I just don't know what it is.
If a mitochondria is not "alive," then is it dead? Even if it is taking part in an active, living cell?
Mitochondria have for many generations now been known to have their own DNA and replicate on their own. So I’m not sure what new distinction is being drawn?
So, the modification would be that we are living in symbiosis with mitochondrial bacteria, similar to how we live in symbiosis with our gut bacteria, rather than them being classified as "organelles" of eukaryote cells.
> A mitochondrion (pl. mitochondria) is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi.
and the "classification" is introduced with
> There are two hypotheses about the origin of mitochondria: endosymbiotic and autogenous.
But if you wanted classify them based on functionality rather than evolutionary history, I'd say they're more like viruses. They have only a handful of genes themselves, and exploits the nucleus' genetic material for all the other proteins it needs to function.
General acceptance of the endosymbiont theory is a relatively recent (much less than 50 years) phenomenon.
There seems to be a strange, half-hubris, half-pride vein that runs through Humanity that would see us as lesser for being hosts to benevolent bacteria, despite us very obviously being unable to survive without benevolent bacteria.
With that level of proofreading, I'm not sure what else was wrong in the article...
It is a videogame based on/continuing a cheesy scifi novel that played with the concept of mitochondria being alive (also sentient). Sure it's not quite scientifically sound, but it still explains the concept with enough actual facts (very easy to distinguish from the fictional ones), and the ludicrous nature of it all makes it so you won't *ever* forget that mitochondria are in fact a part of the cell and their normal function is being involved in energy production.
I can warrant 90% of people who ever thought about the mitochondrion's existence and function (beyond basic school formation) that aren't working or studying in related fields are just people who played this game. I can bet there's a non-zero amount of scientists that got into this stuff because they played the game as kids or teens.
Kek.
> control bioenergetics across the eukaryotic tree of life.
What types of outcomes do we unlock when we can control bioenergetics?
https://x.com/niko_kukushkin/status/1854593093636350387 and https://web.archive.org/web/20170506064530/https://inference...
Excellent book!
I’ve only read The Vital Question, but I felt it was a great introduction to biochem for someone not in the field.
This statement is very interesting for two reasons:
1) We not consider mitochondrial DNA as part of the human genome when it's clearly is and can be used to establish the maternal genetic lineage.
2) Traditionally, we always think of telomere reduction and genetic mutations as the root cause of aging but not mitochondrial genetic damages.
A lot of research is looking into the role of mitochondrial damage as causes for a number of conditions.
The question posed is whether we consider mitochondria to be "alive". It's just a word, who cares. What do we do differently given this assumption?
What practical purpose does studying ancient civilizations have? Why do we send expensive telescopes into space to study faraway galaxies and try to uncover mysteries of the big bang? When can we expect the results from number theory to lower the price of gas at the pump?
Knowing that mitochondria have their own DNA is knowledge. Knowing that they reproduce independently of their home cell is knowledge. Learning whether they evolved from a separate viable organism would be knowledge. Learning whether we can make them viable, or breed them separately, and use them in therapies -- all knowledge.
Whether they are "alive" or not is just the definition of a word.
A subset of scientists want to come up with an operational definition of "What is life", which may or may not include things like viruses and mitochondria. As you say, it's mostly definitional, but by defining this, we can potentially make our understanding match up with the latent reality.
2) By "organism" I assume you mean "cell" since humans have several thousand different species with their own DNA living on or inside the body at any given moment. We can speak of animal cells, which have two (species and mitochondria) - and plant cells, which have three (species, mitochondria, and chloroplasts). If there can be one two or three, I don't see why there couldn't be even more.
3) Mitochondria are usually sequestered within the cell, which limits their exposure to immune cells. The immune system primarily targets pathogens that are outside the host cells. In fact, some pathogens can exploit mitochondrial pathways to evade immune detection - the most famous of which is HIV.
And chloroplasts have separate DNAs from the species ones? That really is also eye-opening.. Biology is full of wonders.
Once you accept mitochondria as alive, you might be motivated to explore its "potential" niche, as described by the author. The example of implanting cross-species mitochondria in human cells (e.g. from a gorilla) might lead to novel therapies.
It's about breaking outside the box of mitochondria having to live inside specific environments.
Edit: to your point, there are plenty of scientists interested in studying viruses and much debate about whether or not they are alive. Ultimately it probably doesn't matter.
I do think when you consider mitochondria to be alive, it broadens the scope of your thinking because you start considering each characteristic of life in relation to mitochondria. You might not be motivated to do that without thinking in those terms.
I think the main point the author is making is to not fall prey to reductive thinking about mitochondria's potential and less about the question of "aliveness". We were all taught about mitochondria producing ATP, but it sounds like it serves many other functions and there's a lot more to explore about its potential in synthetic biology and therapeutics.
This meant, importantly, that we learned cells did not always need to evolve a functionality from scratch, but could acquire it through phagocytosis.
It's also a useful tool for studying evolution for many reasons.
We know they have DNA, we know they reproduce independently of the host cell, we know to a degree why they tend to move to both sides on cell division. We know lots of stuff about them and we can always learn lots more. Whether they are "alive" or not has absolutely no bearing on that, other than to naval-gaze.
This sort of definitional argument is not interesting to me.
For example I could easily see a scientist asking the question, "if mitochrondira are not alive, at which point did the phagocytosis of the initial prokaryotic cell lead to the mitochondria not being alive?" "What components were lost in the cell that lead to the loss of life?" I agree these aren't particularly useful, and are ultimately definitional, but definitions matter a lot in science, especially when paradigms change.
The question in the abstract is not really useful except to answer trick questions in bar trivia.
> It seems Mitochondria are not bound to their host cell; they can travel between different cells. Although different species carry distinct mitochondria, experiments show that mitochondria from one species can be transferred to another.
> In 1997, scientists isolated mitochondria from chimpanzees and gorillas and showed that they are naturally internalized and integrated into human cells. Notably, the addition of external mitochondria even showed therapeutic benefits in heart failure and spinal cord injury. Thus, the potential niche that mitochondria can live in is greater than their effective niche.
So it seems like they are more symbiote than organelle, that's amazing.
This assertion is made but not supported. I don't think I understand the importance of this distinction, assuming that everyone already agrees about the evolutionary and mechanical facts about mitochondria, but as far as I can tell, no one disagrees that mitochondria were originally free living cells, or that they have their own DNA, or any of the other relevant facts about their origins or how they work in the cell. It's merely an argument about what it means to be alive. Which is philosophically interesting, but practically unimportant for the practice of biology.
This seems like a purely semantic debate with no broader importance.
More than 95% of all proteins located in the mitochondrial compartments are encoded by the nuclear DNA, synthesized in cytoplasmic ribosomes and imported into mitochondria. These include factors that regulate mitochondrial DNA (mtDNA) gene expression such as mtDNA and RNA polymerases, mitochondrial transcription factors, RNA processing and modifying enzymes, transcription termination factors, mitochondrial ribosomal proteins, aminoacyl-tRNA synthetases, and translation factors (1, 2).
It's clear that a mitrochondrial element can't live for long without the presence of the host cells, so, like a virus, it doesn't meet all the requirements to be considered fully living.
[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC23071/
Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool.
My biology classes did have us gene editing bacteria to chance its color. That was fun!
> The only one that comes close is Athlete's Foot, which makes the victim sound cool.
The best cure for athletes foot is a 30 minute soak in diluted bleach. Get a wash basin, fill it with warm water, and add enough bleach so that it tingles a little bit.
Do this every other day 3 times, e.g. Monday, Wednesday, Friday. Problem solved.
Make sure to clean out the shoes as well, ideally not wearing any infected shoes for a few days at least, and soak the insides with Lysol a few times to prevent reinfection.
The basis of this technique is that you have skin to spare, and your skin regrows.
Unlike the fungus.
Are there mitochondria in neurons?
Yes [1].
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC7373250/
RBC's don't need them because they are incredibly low-metabolism. It's energetically cheaper for the organism just to make them, let them go for a few months, and then recycle the components.
As far as I’m aware we’ve never worshipped mitochondria. And unless you want to count eating which is technically true but not philosophically so, we don’t sacrifice plants or animals to mitochondria.
The explanation doesn't get much better at higher levels. You have the Krebs cycle which biology people religiously memorize but it doesn't really explain much either. The actual interesting part is usually handwaved away as "magical enzyme/protein" catalysis. Understanding how the mitochondrial proteins/enzyme catalysts function would usually require a graduate degree, and maybe a background in biochemistry and biophysics.
Love this line! Phoenix Worm came to mind.
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)
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?
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/
That could also suggest that any 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
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.
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/
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
https://www.theatlantic.com/health/archive/2012/12/1-458-bac...
>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.
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?
DNA isn't just abstract information, it's also where the first step of protein / enzyme construction occurs. DNA location matters.
SFI Complexity podcast has a few great episodes on this
This presumes that their energy budget was massive to begin with, rather than being selected for over time.
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).
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.)
[1] https://en.wikipedia.org/wiki/Great_Oxidation_Event
[2] https://en.wikipedia.org/wiki/Purple_Earth_hypothesis
Here's a thought, also; maybe once this has happened, it tends to crowd out needing to happen again.
Would love to know the source if you have it.
> 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.
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.
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
If everything however unlikely is likely because creation is unfathomable, sure.
There is nothing specific about our consciousness that makes it unique to earth.
"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."
But how did anyone verify there is an underlying reality outside consciousness? It's just an assumption right?
It's the stuff which continues existing when we stop believing in it.
https://m.youtube.com/watch?v=0lKliaFllPA&t=910s (timeatamped)
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.
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)
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
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.)
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.
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.
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.
What are you basing this on?
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.
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'.
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.
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.
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.
Did we both edit our posts....to improve accuracy, increase resiliency, and to compete ideas?
literally mesa-Q.E.D.
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.
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:
People aren't intimated by people that cannot replace them, they are by people that can.Take it from Roko the Replacer:
But somewhere between a middle school drop out and a super-intelligence and 5-layers QED, I think my posit has merit.Free to continue discussion; but the under the Ego lies the Id, and I'm not well versed in that science yet, still approximating.
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)
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.
I should had clarified, this is lower, more intuitive behavior. It is not, which is why it arises emergently in lower-complexity/class systems.
Beating a rival and taking their energy is awesome!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.
But really, and "slightly" varied instance of yourself is the "most" likely to compete for the same, infinite pool of resources.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
> If we think of mitochondria as non-living organelles, how will we ever harness their full potential?
Whenever anyone uses the "harnessing [its] full potential" cliché, my bullshit alarm starts buzzing. I don't think this article is bullshit, but...we can "harness" as much "potential" as mitochondria have whether we consider them alive or not.