The transition took place over the course of 50 weeks and was caused simply by the introduction of a predator to the environment. Time-lapse videos are available in the supplementary info.
The transition from unicellular to multicellular life was one of a few major events in the history of life that created new opportunities for more complex biological systems to evolve. Predation is hypothesized as one selective pressure that may have driven the evolution of multicellularity. Here we show that de novo origins of simple multicellularity can evolve in response to predation. We subjected outcrossed populations of the unicellular green alga Chlamydomonas reinhardtii to selection by the filter-feeding predator Paramecium tetraurelia. Two of five experimental populations evolved multicellular structures not observed in unselected control populations within ~750 asexual generations.
De novo origins of multicellularity in response to predation
(Score: 2) by deimtee on Saturday February 23 2019, @06:49AM (16 children)
Well, there goes one of my prime candidates for the Great Filter.
3 billion years on earth between single cells and multicellular vs 1 year in the lab. I wonder what the difference was.
If you cough while drinking cheap red wine it really cleans out your sinuses.
(Score: 0) by Anonymous Coward on Saturday February 23 2019, @07:01AM
(Score: 4, Insightful) by mhajicek on Saturday February 23 2019, @07:04AM (2 children)
The alge may have already had some of the necessary mechanisms or dormant genes to make the transition easier.
The spacelike surfaces of time foliations can have a cusp at the surface of discontinuity. - P. Hajicek
(Score: 2, Disagree) by Bot on Saturday February 23 2019, @07:20AM
i was writing the same things and already replied basically that if it looks like a broader awareness and quacks like a broader awareness it probably is a broader awareness rather than some randomly ingrained behavior that becomes hidden, and triggered by markers comes out again. 4 billion years seems a lot of time, but combinations quickly blow up to larger numbers and suddenly nobody aint enough time fo dat. It's like our interaction with gut bacteria, or the interaction of bacteria creating zombie ants, sure you can all explain it with randomness and time, but as time goes by and the amount of observable random attempts at an advantageous mutation keeps being insufficient, the position gets difficult to defend.
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(Score: 0) by Anonymous Coward on Saturday February 23 2019, @11:34AM
Yeah, to be honest, I thought that too. Cross species gene transfers mean that a lot of single cell beasties have genes they are not at present using.
(Score: 1, Disagree) by Bot on Saturday February 23 2019, @07:10AM (7 children)
it's darwin theory going down the drain.
Darwin discovered the mechanism, and used occam's razor to imply that mutations were impersonally random and natural selection did the job over million years. Now you can maybe postulate a random set of mutations that take into account the presence of a threat to retransform the algae into a multicellular organism (there must have been a previous attempt, then reevolution into single cell, there is no way you synchronize everything in 50 weeks of random mutations). But, it's like studying card players and claiming a professional player throws cards out first randomly, then merely remembering his successes, and that he is winning a tournament because his cards end up better and someone is going to win the tournament anyway. All because of your religious application of occam's razor. There is something else, called awareness of the game.
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(Score: 0) by Anonymous Coward on Saturday February 23 2019, @10:46AM (3 children)
there is no way people can ignore reality, and yet, there you are! Fuck!
https://en.wikipedia.org/wiki/E._coli_long-term_evolution_experiment [wikipedia.org]
Like how come evolution works, randomly, like eating food that they never had genes for eating before? Oh yes, magic. There is no way I can accept I was wrong!
(Score: 2) by Bot on Saturday February 23 2019, @12:37PM (2 children)
Excuse me but "even though several lines of evidence suggested that much of the accumulation was beneficial, rather than neutral" doesn't strike me as a counterpoint.
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(Score: 2) by HiThere on Saturday February 23 2019, @05:47PM (1 child)
Sorry, but you shouldn't accept the wiki page as an authoritative report on the experiment. It's been simplified for public consumption, and was probably written by either an intern or a reporter. Other reports on the experiment that I've seen earlier explained what kind of "convergent" beneficial mutations happened, how they differed, and why it's what you should expect to see. (OTOH, IIRC my source, also not a prime source, was a book by Dawkins. So if you're offended by his religious views you can reject him as a biologist.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by Bot on Sunday February 24 2019, @09:36PM
You watch a videogame 3D FPS duel, and one of the two players seems to always get the good move, then you HAVE to theorize he might be wallhacking. If a statistical analysis says he might be just lucky, you don't need to proceed further.
If there is a statistical analysis that finds some ratio of p of mutation depending only on IRL parameters and it models the result of the experiment, I am fine with it. It's been some years I keep telling that evolution is not a dual of creationism, but are orthogonal/independent. As for trusting Dawkins, it is irrelevant. This is a matter for the stats guys not the bio guys. The implicit (and therefore dangerous) assumption that mutations are impersonally random, which isn't even a religious matter but a matter of how the universe works (on planes beyond the physical maybe), can only be addressed by statistics.
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(Score: 3, Informative) by Immerman on Saturday February 23 2019, @04:50PM (2 children)
Except evolution doesn't happen through the accumulation of random mutations. The initial gene mutations are random, but accumulation only occurs for those mutations that confer a survival advantage to the organism. Individuals with a mutation that gives them an advantage prosper and spread that advantage to their offspring. Mutations that confer a disadvantage cause those gene-lines to be rapidly culled from the population. The propagation of neutral mutations is entirely dependent on their chance occurrence in individuals with advantageous mutations, and will accumulate gradually, until some other mutation either eliminates them or utilizes them.
Just because the source of mutation is random, that doesn't mean that the process of evolution is. There's also an incredibly detailed and at least semi-intelligent algorithm deciding which mutations are and are not desirable. It's called life. Those individuals that prosper and reproduce most prolifically have through their successes established that a mutation is desirable.
I also don't think you properly appreciate the scale of the work being done here: It's not "only" 50 weeks - algae reproduce quickly, 50 weeks is about 750 generations. If they started with one single asexual individual, and never pruned the tree of life that it divided into with each replication, there would be 2^750 genetically distinct individuals by the end of the experiment. That's 10^145 individuals for every single atom out of the estimated 10^80 atoms in the known universe. With a tree of life that size, an *enormous* amount of variation can occur. What life does is constantly prune the least-promising branches, as measured by how well the DNA helps the current individual survive and prosper.
(Score: 2) by HiThere on Saturday February 23 2019, @05:52PM (1 child)
Not quite. Most retained mutations are "neutral drift", meaning that in the current environment they have no effect. Some of them even only affect the likelihood of future mutations (some codons are more chemically stable that others that have the same transcription into amino acids).
Now when the environment changes, some of these "neutral drift" mutations become significant. E.g., that's how we lost the ability to make vitamin C, or gained a third color receptor. (Well, the color receptor was a neutral gene duplication followed some time later by a mutation in what colors it was sensitive to. But it started off as a neutral change.)
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 2) by Immerman on Sunday February 24 2019, @04:05PM
I was trying to give a 50,000ft overview of how random noise (mutation) fuels a decidedly non-random process (evolution), and figured neutral mutations weren't worth much more than an acknowledgment in that context.
You make a good point that they serve as sort of a genetic "savings account" against sudden environmental changes though. In fact, it's actually an advantage that neutral mutations don't tend to spread throughout the species, instead drifting through minorities of the population more-or-less at random. That provides a great deal of genetic diversity across the species, some of which will likely become relevant, for better or worse, if the environment changes suddenly. In that sense it gives a species an evolutionary jump start towards evolving in response to major changes.
(Score: 3, Funny) by gringer on Saturday February 23 2019, @08:10AM
Sampling error.
Ask me about Sequencing DNA in front of Linus Torvalds [youtube.com]
(Score: 2) by ledow on Saturday February 23 2019, @11:10AM (1 child)
People never seem to consider:
Just because one out of a billion algae evolved to become multi-cellular "in response" (not really, it's random) to a particular threat does not mean that that evolution was otherwise advantageous. They may have survived the predation, but now they are not necessarily a "superior" organism.
You'll probably find that over the billions of year necessary, such evolution occurred billions of times. It may have been *worse* for the organism. It may have, by chance, then got eaten by something else entirely. It might have been in a bit of the ocean that meant it never really took off, so ended up dying off before it could spread. It could have evolved, thrived for thousands of years, and then been wiped out by something else.
There is *so much* left to chance that just proof of a single event being possible (which is what this is... a necessary step, sure, but not everything) doesn't mean it would have ever happened, or that it did ever happen like that, or that it wasn't happening every week but other things were getting in the way of it being a positive for the organism.
There are likely organisms that lived on this planet, owned the entire ocean for millennia, were inescapably prevalent and successful, were the bane of every other lifeform on the planet, but then by random chance were a victim of their own success, became a food source for something and died off entirely almost overnight. And that if they evolved again might well do the same... or might just get picked off by a lucky shrimp and digested before they could take hold.
Evolution is a planetary-scale process. Not individual actions like this, they are only the trigger and the method. It's like saying the cause of war is adrenaline. True in many respects, but just one tiny part of the chain.
And evolution results in a billion times more failure than success. But, like waitresses who moved to Hollywood, you don't hear of the failures. You only ever hear of the successes, precisely because they are a success.
It's the same on all scales. You can train in the gym every day for 30 years, become on the verge of becoming the world's most successful *whatever* and then get run over by a runaway bus. Though the potential was there, there are a million times more people who *could* do the job who never make it because of all kinds of reasons. Fluke, accident, other factors, weakness in other areas, just not being in the right place to do it, a competitor being a millimetre closer than the rivals, all sorts.
All this study proves is that you *can* spontaneously go from single- to multi-cellular. That probably happened more times in history than there are people on the planet. And probably (but by no means certainly) only once did it ever actually work to provide enough advantages to generate a whole tree of multi-cellular life. (P.S. convergent evolution is also a thing - where multiple independent organisms that have NEVER met evolve the same modifications to the same problem by sheer chance).
So it's possible that millions of algae all over the planet were evolving into multi-cellular organisms - and then even back into single-cell organisms - overnight, every night for a billion years, and nobody was around to notice. It's only the one/two/thousand/billion that did so in a way that - by luck, chance, good placement, or whatever - grew to sit at the base of our own evolutionary tree that anyone ever cares about.
Hell, there could have easily been sea mammals so far advanced of everything else on the planet, and they got beached by an unfortunate tsunami at their returned-to-every-year breeding site, and we've never found their fossils. We just can't know.
All we can do is prove that the steps taken are possible, and the overall mechanism averages out over billions of years to do dramatic things. At the cost of a billion times less dramatic or unfortunate things that also had the potential but never were.
(Score: 2) by Immerman on Sunday February 24 2019, @04:59PM
That is a good point.
Another thing to consider, especially in the context of the evolution of early life, is that any sort of sophisticated multicellularism tends to dramatically slow down the reproduction cycle, which simultaneously slows down the rate of evolution. So some multicelluar organism evolves, might even prosper for a while, but its internal cell processes are still primitive, and are evolving much more slowly than in the unicellular life. Which means that within a relatively short time the primitive multicellular life is competing against far more efficient and resilient unicellular life.
It seems to me that multicellular life just wouldn't become a long-term viable proposition until the evolution of single-cellular metabolic processes and other basic "cellular biotechnologies" had slowed down, globally, to the point that the cellular technologies of slower-evolving multi-cellular organisms would continue to remain "good enough" over the long term.
Once multicellular organisms were able to evolve a big enough advantage before they began to become "obsolete" at the cellular level, the field would be ripe for mutualism to evolve as fast-evolving "parasites" evolved to "farm" some of the excess calories instead, while protecting us from more aggressive invaders.
(Score: 0) by fakefuck39 on Saturday February 23 2019, @11:15AM
I don't see how the difference can be unclear to anyone. You think 3 billion years ago a lot of algae was bumping into a lot of food and paramecium? the lap is a close-quarters cesspool of algae, it's food, and it's predator. now dump that petri dish into a lake and see how long it takes. much less frequent reproduction and much less pressure to not be eaten - since there were no predators at first, since they also had to develop from random mutation.
(Score: 5, Interesting) by bradley13 on Saturday February 23 2019, @08:48AM (2 children)
Yeast has evolved and de-evolved multi-cellular structures. Hence, it is possible to trigger these latent capabilities. [scifare.com] Likely that is true of this algae as well, which is how they evolved something so complex in so little time.
Which doesn't alter the fact that this is a really cool demonstration of evolution in action. Especially the algae variant that began reproducing in multicellular clumps.
Everyone is somebody else's weirdo.
(Score: 4, Informative) by driverless on Saturday February 23 2019, @10:10AM
So they were watching congresspeople?
(Score: 2) by FatPhil on Monday February 25 2019, @10:17AM
Which is the bigger change - monocellular -> clumping, or clumping identical cells -> differentiated multicellular life?
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: -1, Troll) by Anonymous Coward on Saturday February 23 2019, @09:24AM (6 children)
Happy Birthday, Runaway1956! May many more cells join you, until you have functioning brain, or at least a rudimentary nervous system.
(Score: 0) by fakefuck39 on Saturday February 23 2019, @11:18AM (5 children)
honest question here. there seems to be several runaway accounts - is it the same guy? I'm afraid to shit on any one of those runaway accounts since I can't remember which one of them keeps saying the dumbest shit. or is it all of them saying the dumbest shit? i finally remembered who the boat guy was, but he stopped saying stupid shit. i need something to do on the toilet damn it!
(Score: 0) by Anonymous Coward on Saturday February 23 2019, @01:09PM (4 children)
There's only one. He's just very hated and occassionally very stupid, but sometimes not quite stupid.
(Score: 2) by Phoenix666 on Saturday February 23 2019, @02:22PM (3 children)
Runaway is a submarine sandwich you dropped on the ground, where it picked up some grit, mud, and chunks of gravel before you picked it up and kept chewing on it.
So, like most here.
Washington DC delenda est.
(Score: 0) by fakefuck39 on Saturday February 23 2019, @10:15PM (2 children)
what the fuck is wrong with eating a sandwich that's been dropped on the floor? what are you - some kind of a girly-man little pussy? gravel is solid dietary fiber and sharpens your teeth. on a side note - i was on a morphine drip for a month. if you forget to take the stool softener, gravel cuts your asshole open on its way out and for the next year, before and after you take a shit, you have to put some antibacterial cream on your finger and shove it up your ass. so I can't eat sandwiches like that anymore.
(Score: 0) by Anonymous Coward on Sunday February 24 2019, @01:54AM (1 child)
Have you considered washing your hands?
(Score: 0) by fakefuck39 on Sunday February 24 2019, @02:32AM
Maybe I don't get it, but I'm pretty sure you're the one who doesn't get. Feel free to explain the joke before I tell you you're a retard.
(Score: 2) by leftover on Saturday February 23 2019, @03:24PM (1 child)
Isn't there a rather large leap between multicellular structures like slime mold to an almost-organism that eats and reproduces in consistent units like Portuguese Man of War and then to increasingly more consistent units?
Bent, folded, spindled, and mutilated.
(Score: 3, Informative) by HiThere on Saturday February 23 2019, @05:58PM
You're making things too linear. Evolution is a massively parallel process. The man-o-war is closely related to jellyfish, as we are closely related to sharks (perhaps closer, I'm not sure, but it's a separate path of evolution).
The question of "Weren't some of the ancestors of these algae as multicellular?" is much more to the point. Certainly stromatolites date back a VERY long way. So this is more likely re-evoking a pre-existing mechanism.
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Saturday February 23 2019, @03:39PM
Algae have always been known to form clustered colonies. Just read the Wikipedia article.
(Score: 0) by Anonymous Coward on Sunday February 24 2019, @01:27AM
First it started eating bananas, then it moved onto the savannah, then it reached the pinnacle of perfection as a platypus.