My name is LUCA, I live on the ocean floor.

October 8, 2011 5:09 PM

Scientists have come closer to finding the common ancestor of all Earth life. The last common universal ancestor (LUCA) is an idea that goes back to Charles Darwin's On the Origin of Species and whose existence is supported by the fact that all Earth life is based on DNA. But the tantalizing search is getting closer, primarily based on the question, "Which features of the archaea, bacteria and eukaryotes can be traced back to their common ancestor, LUCA?"
posted by Renoroc (34 comments total)

Admit it. The post was an excuse for the title.
posted by Trurl at 5:11 PM on October 8, 2011 [21 favorites]

Cool Hand LUCA.
posted by flapjax at midnite at 5:18 PM on October 8, 2011 [1 favorite]

They're looking for LUCA? That's easy: He lives on the Second Floor.
posted by Dr. Zira at 5:29 PM on October 8, 2011 [3 favorites]

Damn it, I didn't see the post title. Suzanne Vega for the block.
posted by Dr. Zira at 5:31 PM on October 8, 2011 [2 favorites]

I like the zeolite theory. Very basic and plausible.
posted by Blazecock Pileon at 5:32 PM on October 8, 2011

Uh, have they checked Tom's Diner?

Holy shit, remixed by DNA.
posted by codswallop at 5:49 PM on October 8, 2011 [9 favorites]

Soooo, while the search is "getting closer", there isn't anything to be excited just yet, no? bummer..
posted by c13 at 5:55 PM on October 8, 2011

We're through the looking glass here, people!
posted by Threeway Handshake at 5:55 PM on October 8, 2011

They just need to listen harder, since blood makes noise.

come at me bro
posted by Uther Bentrazor at 5:57 PM on October 8, 2011 [3 favorites]

last common universal ancestor (LUCA)

I've detected a mutation.
posted by DU at 6:08 PM on October 8, 2011 [14 favorites]

They should look on the second floor.
posted by ian1977 at 6:14 PM on October 8, 2011

"Captain, I have found another suitable planet sir"

"Bring it up on the viewscreen.... Looks promising. Load a comet with LUCA and lets see what happens"
posted by Bighappyfunhouse at 6:18 PM on October 8, 2011 [3 favorites]

One thing that I hadn't thought of until mentioned in the Stephen Stearns biology course I watched at iTunes U is that, if you make the reasonable assumptions that we are descended from a LUCA, and that LUCA evolved from some pre-biotic chemical system, then actually we, and all life, evolved from some self-perpetuating chemical reaction.
posted by snofoam at 6:23 PM on October 8, 2011

It's interesting that modern bacteria may actually be substantially less complex than the Common Ancestor. The overall goal is to reproduce, and doing the same thing with less energy (becoming simpler) is one strategy that obviously works. The super-successful organism that gave rise to all forms of life we know about may have outcompeted everything else through complexity.... we simply don't know.

And make no mistake, even the lowliest of bacteria are unbelievably complex machines. There's a reason it took about a billion years to come up with even single-celled organisms. And going from there to multicellular life was another staggering leap. The subsequent, highly visible changes, and explosion of species and methods of locomotion and sensory methods, took far, far less time than just coming up with the basic processes for first keeping a single cell alive, and then working out how to live in larger groups. We pay attention to the big changes (how different birds are from, say, monkeys). The easily visible changes are the ones that capture our imaginations. But based on how long they took, those large changes were far less difficult than the small ones in the beginning.

If there was more than one abiogenesis (life from non-life) event, there may have been a true mass extinction in the far, far distant past, in which every living thing on the planet, except the Common Ancestor and its descendants, died.

However, I saw some musing a year or two ago that that there may be lots of living things we haven't found yet, even right under our noses, because we don't know what to look for. Particularly in samples of deep seawater, we find complex biological compounds all the time, and don't know where they came from.
posted by Malor at 6:39 PM on October 8, 2011 [7 favorites]

Damn it, I didn't see the post title. Suzanne Vega for the block.

double damn.
posted by ian1977 at 6:42 PM on October 8, 2011

"the important thing is that this specific organelle is found not only in all multicellular organisms but also bacteria and their cousins the archaea"

We're all "cousins", of course, but I think that archaea are more closely related to us than either of us are to bacteria, right?
posted by Flunkie at 6:48 PM on October 8, 2011

Is LUCA on the second floo

dammit.
posted by IAmBroom at 6:54 PM on October 8, 2011 [7 favorites]

This is my great great great uncle Luka. He gets too drunk at parties and is quite embarrassing, but we love him because he's family. Please keep him away from the liquor -- beer is okay. Oh, and he chases redheads so warn your sister.
posted by hippybear at 7:05 PM on October 8, 2011

Is there any argument that viruses depend upon this organelle?
posted by jeffburdges at 7:08 PM on October 8, 2011

Fascinating article, thanks for sharing.


I remember reading a Heavy Metal issue a very long time ago that had a couple of aliens visiting a primordial planet. One had to defecate and did so right into the river/swamp. They had a laugh on what sort of impact such organic material, bacteria, and what not might have on the planet millions of years later. Of course that planet was earth
posted by 2manyusernames at 7:27 PM on October 8, 2011 [4 favorites]

One reason they can't learn more about LUCA is every time they ask directly, it responds "Just don't ask me how I am, Just don't ask me how I am, Just don't ask me how I am."
posted by oneswellfoop at 7:34 PM on October 8, 2011 [2 favorites]

jeffburdges, viruses only carry what DNA or RNA they need in order to replicate. They are obligated to use host mechanisms to survive and reproduce. They store nothing, the organism they infect (you, me, a plant, a bug, a bacterium even) will provide everything but "the instructions" to do so.

They travel light.
posted by ltracey at 7:37 PM on October 8, 2011 [1 favorite]

The discussion going on in the comments on that io9 article makes me want to weep for America.
posted by waitingtoderail at 7:40 PM on October 8, 2011 [2 favorites]

My name may be LUCA now, but it used to be Mud.
posted by cthuljew at 7:44 PM on October 8, 2011 [1 favorite]

Yes, I roughly understand how viruses work, ltracey. I'll elaborate upon the question : Do viruses directly depend upon this organelle? Presumably, yes. Is there any evidence they evolved from 'real' cells after it evolved? Umm, that's damn tricky. We're fairly confident they evolved from real cells somehow, but how & when? Do we even know the process of 'original' virus formation is not ongoing?
posted by jeffburdges at 8:34 PM on October 8, 2011

Old hotness - Darwin fish, car emblem
New hotness - Luca chemical stew, car emblem.
posted by Bighappyfunhouse at 8:41 PM on October 8, 2011

i watched a NOVA about the human genome project, they claimed to have found the bacteria, an extremophile that lives in volcanic mud, dug up near Mt Etna in Sicily. They said that this bacteria has only its own DNA, and everything else has some of it. The scientist was a happy, beer drinking, German, driving a BMW. But it seemed plausible to me at the viewing. They said this bacteria, because it is such an extremophile, likely lives in the margins of the magma all over the earth. So, I am not sure which hair these guys are splitting, maybe they should watch more PBS. Just kidding, but not about the common ancestor.
posted by Oyéah at 9:00 PM on October 8, 2011 [1 favorite]

Oh, also, my second shout out to Peter Watts's Blindsight in as many days.
posted by cthuljew at 9:18 PM on October 8, 2011

By the way, I would like to register my extreme disapproval at being earwormed so thoroughly. Argh!

*leaves, humming but unhappy*
posted by Malor at 10:22 PM on October 8, 2011 [1 favorite]

Awesome stuff. And after several billion years of evolution, creatures were created that don't even believe in evolution. The irony. I sometimes wonder if religious people don't believe in evolution as they can't get their head round the time lengths involved, although who can? Was it Hawkins whio said no one could comprehend the scales of time and space, the vast distances and vanishingly small scale of the atom etc.
posted by marienbad at 12:55 AM on October 9, 2011 [1 favorite]

I think the framing of LUCA is a bit off. It is more likely there was a pool of common single cell ancestors that had these traits. Single cell organisms reproduce asexually. One bacteria splits into two bacteria. In this method natural selection occurs through random mutations with populations of mutants surviving depending on the changing conditions. However bacteria can also directly transfer DNA to each other via a few mechanisms.
One is called plasmids. These are small circular rings of DNA that when bacteria bump into each they can share. This is the primary method that bacteria are believed to gain antibiotic resistant genes. This method actually requires the bacteria to actually share a bit of their cytoplasm(fluid contained in their cytoplasm) and allow the genes to move over. This process is highly controlled by proteins It is likely ancient cells an uncontrolled version of this was happening with cells bumping into each other and sharing various bits of protein, genetic material, and various other molecules if not fusing together out right.
The other methods transposoon, directly taking up naked DNA from the surrounding environment, and viruses require a common metabolic machinery(DNA->RNA->Proteins) so what ever proteins are encoded by the transfered genetic material gets made into the same thing. Not to say that there weren't happening before LUCA, but they probably were a lot more random in what they produced, because two cells could use a different translation pattern for RNA to Proteins.
As for jeff bridges question. Viruses don't directly depend on these organelles. Most of the prokaryotic organelles(e.g. carboxysome) produce energy for the cell and therefore viruses to use in the production of proteins. However the interesting about them is that since they look fairly similar to viral capsid proteins leading to speculation that viruses and these prokaryotic organelles share a common origin.
posted by roguewraith at 5:29 AM on October 9, 2011 [4 favorites]

"Noodly appendage" is a metaphor for "strand of DNA". Yarr!
posted by Xoebe at 11:43 AM on October 9, 2011

Luca sleeps with the fishes.

This original organism might actually have been more complicated than some of the bacteria and archaea that came after it.

This had not occurred to me. Very interesting.

It's kinda funny, not funny 'ha ha' so much as a make-you-think funny, that the discussion (in the posted piece) takes a left turn into creationism.
I mean this is basic biology. Not simplistic, but pretty straightforward linear progression type science: "if a particular structure is found in every form of life, then that means it has to have evolved in the common ancestor."
I understand this and I was not an organic chemistry major. It's high school level stuff (to thumbnail and understand the explanation), like "mitochondria" or "nucleus." Pretty sure they mentioned that in class at some point before I cut out early to take a nap in study hall.

Point being, at what level does biological science have to be to preclude a discussion of theory?
"Man, I took a mean crap this morning"
"Well, you can thank God for that!"
"As a matter of fact, I did. But purely as metaphor."
"Then you are damned sirrah!"


It is likely ancient cells an uncontrolled version of this was happening with cells bumping into each other and sharing various bits of protein, genetic material, and various other molecules if not fusing together out right.

(If you know what he means...)

So the idea is there wouldn't be a common singular universal ancestor the way there would be one mutant who spawned everybody else because it was so successful but rather a pool of mutants sort of bootstrapping each other?
Would the organisms be living in a sort of protein soup where taking up floating DNA was an option or would it be a sort of Brownian motion thing or more of a self-organization thing?
(just curious, your comment made my brain go and I missed some class a bit back)
posted by Smedleyman at 4:44 PM on October 9, 2011

Well, right, roguewraith, perhaps the individual bits that made up the Common Ancestor were evolved in different organisms, but ultimately, at least as far as we can tell from the DNA evidence, everything combined down to just one super-successful organism that was so good it wiped out all other life on earth. That individual germ probably didn't wipe out everything all by itself, it probably gave rise to new species that branched out into the other niches that were being inhabited by the life that didn't survive, but ultimately, it looks like there's a single organism from which the entire Tree of Life springs.

In that metaphor, you could think of the individual bits of evolution that were shared as the roots that gave rise to the trunk.... although the image kinda breaks down, because trunks don't generally go extinct without killing the rest of the tree.

You're thinking that the Common Ancestor was a web, that the source of life was a bunch of different subtrees that just kept all mixing together, and that there was never a true single grandparent organism. I'm not a biologist, but I don't think the DNA evidence supports that idea. It looks like it all channeled down to just one species, and presumably, one single cell that finally had everything just exactly right.

If you see any evidence from real biologists that contradicts this post, give it more credence than my explanation, as I'm just a moderately informed layperson. And new evidence contradicting the Single Source idea could always pop up later. But right now, I believe our best guess is just one grandparent cell for everything.
posted by Malor at 4:54 PM on October 9, 2011