Ignoring the inconceivably remote chance of life forming from non-life, it's very very rare for simple life to evolve into more complicated life. Also, we just realized that cells need to get bigger to get more complex, and that somehow isn't just 'another' mutation.
And then the title? There is nothing about how or why complex life only evolved once. Just that it was unlikely. Chance of life forming from non life * age of the universe * number of stars * the chance a star has an earth like planet, is far from zero.
I wouldn't even bother ranting but this was number 3 on the front page.
The original article [1] is titled "The energetics of genome complexity", which is much more reasonable. It argues that the energy processing of mitochondria was necessary in order for eukaryotes to expand in complexity.
The article is behind a paywall, so I can't read the details.
Anecdotically, there exist anaerobic eukariot cells that live on hydrogenosomes [2]. I don't know if they were originally aerobic and lost their mitochondria, or if they evolved in parallel.
There also exist sea slugs that live in symbiosis with the chloroplasts of the algae they eat [3], so this kind of symbiosis has happened more than once.
One of the perks of working for a school... I'll try to summarize as best I can:
The main calculation in the Nature paper is the energy budget of a cell. They give the example of E. coli: "to raise gene number tenfold, E. coli must also increase its energy budget by close to tenfold; and therein lies the problem." The reason so much more energy is required is due to protein synthesis (DNA codes to RNA which codes proteins, if you're unfamiliar with genetics). So obviously with a larger genome, there's more proteins to synthesize, and this cannot be accomplished by simply making fewer copies of the old proteins. If anything, you need more of some of those original proteins as infrastructure support for this new Genome 2.0.
So (and this is my wording) prokaryotes are at a local maximum for genome and cell size. Chucking mitochondria into the picture provides the wattage (literally) for them to reach a much greater genome and cell size, and therefore organismic complexity.
I am unclear about why the acquisition of mitochondria by a cell is considered to be such an unlikely event, as I lean towards the view that given enough cells/space/time, unlikely short term possibilities become distinct probabilities eventually. Also, I can't help wondering if the reason that simple cells are not observed to absorb free mitochondria is that eukaryotic cells and the organisms they evolved into have somehow poisoned the well, or attacked newly-complex competitors so aggressively that they've suppressed the population of omnivorous simple cells.
But I'm no biologist. Am I missing something obvious, or is there a particular paper explaining why this mitochondrial upgrade is considered such an unlikely event?
I would guess if one prokaryote engulfs another, it's highly unlikely that both of them are going to survive the experience, much less that both will thrive and evolve a symbiotic relationship, much less that this relationship will persist through cell divisions into subsequent generations. Both organisms would have to be uniquely suited to the relationship in the first place.
I upvote based on content not title. Perhaps a mod can change it to "New theory suggests Mitochondria precede complexity in early life" I definitely would classify engulfing mitochondria as not just another mutation, it's an entirely different thing.
Then everything is an entirely different thing. The simple act of a single cell engulfing mitochondria is not the birth of a species.
Even on content I would bury this if I had the button for it, it makes pretty heavy claims without any evidence and necessarily brushing aside fundamental problems with the overall conclusion.
I am not bashing the scientific article that this editorial is 'about'; but the article itself, besides a tiny nugget about the necessity of mitochondria being perhaps otherwise overlooked, it is just drivel.
The last part of your post is known as the Drake Equation (http://en.wikipedia.org/wiki/Drake_equation). I'm guessing you've probably heard of it, but it could be of interest to other people, so I figured I'd link it.
Tangent: the Drake Equation seems to be the template for a class of "Google interview" questions: estimate something you can't really know, at least off the top of your head, in which you then start to identify factors, and start to guess at upper and lower bounds, to come back with a plausible answer, or at least a range. I suppose a lot of research is like that, but the Drake just happens to deal with factors that are harder to measure.
"Chance of life forming from non life * age of the universe * number of stars * the chance a star has an earth like planet, is far from zero"
You have no proof for this, and things can well be the other way round. Let
n = age of the universe * number of stars * the chance a star has an Earth like planet
n is a number that we currently have a pretty good guess at. Let p = chance of life forming from non life on Earth-like planet within a given year. We are basically clueless as to the value of p. p may well be much less than 1/n, which would make our biosphere very special indeed.
I have no proof for it, but I don't need it. The burden of proof is not on me. They are making the claim that 'complex life only happened once'.
Life certainly does exist so p > 0. Since our understanding (or I should say, my under standing of 'our' understanding) of n is approaching infinity, it stands to reason that p x n is > 0.
You've made a statement that a certain quantity is far larger than zero, so you do incur a burden of proof for that statement. p * n > 0 doesn't imply p * n >> 0, not even for large values of n (and "approaching infinity" doesn't apply to constants).
Sorry, 'far from zero' is really meaningless and I shouldn't have said it that way. I don't actually mean to make a positive statement about the existence of complex life elsewhere in the universe, though intuitively I think it's absurd to believe our little planet is the only one with life on it. I mean, why would we believe that other than residual religious dogma?
"I mean, why would we believe that other than residual religious dogma?"
Because when we look out into the universe, it looks like we expect it to look when it is dead, not full of life, some significant percentage of which becomes intelligent. Nothing that looks like Dyson spheres of any form (recalling that the "solid shell" is actually only a special case), nothing that looks like curated stellar evolution (very high-end stuff but a truly advanced civilization will not want to leave stars just randomly flying around a galaxy and exploding), very very little that could even conceivably be a ship traveling between the stars (which turns out with any physically-plausible propulsion mechanism to be visible from a very long ways away and would show very clear blue/red shift changes), nothing that doesn't appear entirely natural.
This isn't the whole story (maybe they're hiding, maybe our idea of the top end of tech is wrong, maybe they're all virtual, maybe they escaped into another, friendlier dimension, maybe they all kill themselves, maybe the universe is soaked with simple life but this article is essentially correct and complex intelligent life really is a 10^-1000 event, etc.), but it is not true that the claim that complex life must be hard is some sort of stupid idea in light of the size of the universe. Arguably it's actually the claim best supported by the evidence at this time.
People are really bad at thinking about small probabilities even on the scale of one out of a million, and it's not impossible that complex intelligent life turns out to be one out of 10^1000 or worse; we simply don't know. It is not hard to come up with calculations that plausibly set the odds of advanced life occurring even once in the universe as less than 50/50 without having to make stuff up. Our ignorance dominates our knowledge here.
Where exactly would we be seeing all this stuff? I mean, how closely can we even look on planets in our galaxy? We are still discovering trillions of new galaxies here and there.
Our reach is virtually zero in the context of the universe. It seems from our vantage point, I would expect the universe to look exactly the same whether it was bustling with life or we were the only ones.
I had never thought about searching for Dyson spheres (it made me replay a part from The Big Lebowski where the dude says, "We'll that's fucking interesting man."), but they strike me as a incredibly hard thing to search for. Don't we see into the universe with the energy escaping from stars, galaxies, etc..? If some species were able to actually harvest the output of a star to anything approaching 100%, wouldn't it be exactly the type of thing we would never see?
> Arguably it's actually the best claim supported by evidence
Unless I am fundamentally wrong about the resolution of our map of the universe, I don't think there is any evidence either way unless you believe in any 'encounters'
"If some species were able to actually harvest the output of a star to anything approaching 100%, wouldn't it be exactly the type of thing we would never see?"
You'd still have residual heat. Some have suggested that what we'd see is awfully similar to red giants though I rather expect we'd still see something odd about them.
Besides, the one you really should have focused on is star-traversing ships. They're visible from a really long ways away.
"I would expect the universe to look exactly the same whether it was bustling with life or we were the only ones."
Allow me to re-add in the word "intelligent" to your "life". The universe looks the way it would be expected to work if absolutely nobody ever makes it off their planet to any reasonable degree, or there is no other intelligent life out there. Or we just happen to be the "precursors".
Part of the problem with this debate is that most people are still participating in it with very 1960s ideas about the limits of technology, very Star Trek ideas about what technologically sophisticated aliens will be like. Of course the Federation could be floating around out there without us knowing, with its starships powered by magic, its technologies powered by magic, and humanoid aliens scattered about everywhere due to magic. (Yes, I know about the episode in question.) But that's not what it looks like. In reality, a modern conception of what a technologically-sophisticated culture would do results in a lot of things visible from a very great distance, the ones I previously mentioned before. And we see 0 of them.
Personally I do not put much stock in the idea that intelligent life is abundant and easy and not a single one of them ever decides to go to another star. For such a society it just isn't that hard and the payoff of being the first in a star system is incomprehensibly enormous, well out of proportion to the difficulty of getting there. Something about standard story of easy, abundant intelligent life is very very wrong, and the most parsimonious explanation is that intelligent life is in fact not easy or abundant.
What? No. If there is residual heat you aren't capturing all the energy.
> In reality, a modern conception of what a technologically-sophisticated culture would do results in a lot of things visible from a very great distance, the ones I previously mentioned before. And we see 0 of them.
This appears to be the crux of your argument. Can you go into or point to a place where I can find out more about what these ships would supposedly look like?
I think the fact that we will almost certainly need a paradigm change before we can really conceive of interstellar travel combined with the radical shift in conceived ideas following a paradigm shift, current guesses about what a super advanced culture's vehicles act like doesn't really hold much weight for me.
You can't capture all the energy. Basic thermodynamics. You have to black-body radiate away the heat of the star driving the system, or the only alternative is that it is all collecting within the system, cooking everybody within in a fairly short period of time.
I argue on the basis of real science that we know, not because we know it all but because we can't argue on the basis of science we don't know about. Given that, we damn well can make some guesses about what a space ship will look like, which inevitably includes some form of propulsion involving either the expulsion of very, very hot matter (to get optimum mass efficiency, propellant will be at a premium and no point dumping it out the back cold) or light directly (unlikely but at least plausible) in a directional manner.
The topic came up a few months ago during the discussions on whether it is rational for an alien civilization to summarily execute any other civilizations it discovers with relativistic planet-killers, but unfortunately trying to Google up a specific discussion about spaceships and relativistic projectiles is an exercise in futility. Still, work the math on what it takes to get a decent payload (at least several thousand tons would be nice) up to ~.1c, and then recognize that thanks to Newton's laws, the resulting mass-energy number you find must actually be coming out the back of your spacecraft in as close to a single direction as possible. Possibly literally as a laser, though as I said I'm pretty skeptical about the utility of a pure light-drive. It's pretty damned bright.
Look, I hate to be offensive, but if you don't fail basic thermodynamics and you actually take seriously the real science we already know, we don't have to retreat into romantic cliches about how we can't possibly understand advanced cultures. We can in fact put bounds on things if our understandings are basically correct, and if our understandings are basically incorrect then frankly we have bigger problems than the question of alien life.
The upshot of this, going back to your first post, is that if either of us is retreating into "religious dogma", romantic conceptions of reality held onto despite rational examinations of the evidence and science, taking shelter in the possibility of who-knows-what magic science may produce in the future and refusing to use what we already know, it's you, not me.
Look, it's not offensive but I do think what you're saying is naive.
Lets take a step back into the 1500s and talk about what an advanced culture able to move thousands of tons of goods from one side of the country to the otherside in a matter of days would look like. or what being able to search all of the worlds knowledge instantly would look like, etc etc. Any of their guesses are necessarily limited to their 'limited' perspectives.
We have had numerous paradigm shifts since then, each giving fundamentally new ways to conceive of problems, and I think it's incredibly likely that we will undergo another paradigm shift with regard to physics/space travel before our society is leaving the solar system, let alone the galaxy. If that's the case it's not an unnecessary romantic conception, it's a necessary repercussion of a historically verifiable phenomenon, paradigms change, and so do ways of thinking about problems.
Besides, I still don't understand how we are seeing a several-ton payload going .1c in a galaxy we just discovered.
I guess I just don't see a compelling argument that we would, from our vantage point and with our tools be able to make any type of reasonable observation against a hypothesis about other intelligent life.
To play the role of "guy who links to a relevant wikipedia page" again, the conflict between the fact that we've seen no observations of intelligent life out there and our estimates that our life is not unique is known as the Fermi Paradox (http://en.wikipedia.org/wiki/Fermi_paradox). Once again, you may already know this, but it will hopefully be interesting reading to someone else.
> "intuitively I think it's absurd to believe our little planet is the only one with life on it."
Intuition is often wrong, especially when it comes to probability.
We have n planets, which we can rewrite as 10^x. There's a probability to evolve complex life of 10^-y on any given planet. Which is bigger, x or y? By how much? What are your error bounds? I've seen people throw out numbers with thirty zeros after them and think they've made a point, but really, either x or y could be much bigger than 30. There could be complex life on 10^many planets, or it could be a total fluke that it exists even on this one.
Either way, your intuition isn't going to tell you anything meaningful.
hrm, I don't think that's true that there is nothing to be learned from our intuition on this.
10^-y could be anywhere from 0 to 1, but you have to be extremely close to 0 for y to be bigger than x. Since we are here pondering this, it makes intuitive sense that it's likely we 10^-y isn't infinitesimally close to zero.
Isn't the optimistic guess at Drake 2 or something (correct me if I'm wrong)? That's not /very/ far from zero, and if you consider that it's the number in the Milky Way I'd say that's pretty very much close to zero.
Article tl;dr:
Ignoring the inconceivably remote chance of life forming from non-life, it's very very rare for simple life to evolve into more complicated life. Also, we just realized that cells need to get bigger to get more complex, and that somehow isn't just 'another' mutation.
And then the title? There is nothing about how or why complex life only evolved once. Just that it was unlikely. Chance of life forming from non life * age of the universe * number of stars * the chance a star has an earth like planet, is far from zero.
I wouldn't even bother ranting but this was number 3 on the front page.