[HN Gopher] Stromatolites: A Billion-Year-Old Living Organism
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Stromatolites: A Billion-Year-Old Living Organism
Author : pseudolus
Score : 87 points
Date : 2021-01-18 13:00 UTC (10 hours ago)
(HTM) web link (www.bbc.com)
(TXT) w3m dump (www.bbc.com)
| cheph wrote:
| I am not sure by what criteria you can say these are billion year
| old living organisms.
|
| If you meant they have been around that long, sure, they have,
| but a stromatolite is not a living organism by most (if not all?)
| definitions. It is a layered sedimentary formation. It is about
| as much an organism as an ant heap without ants is an organism.
|
| And I'm pretty sure that none of the individual organisms that
| create stromatolites are even close to a 100 years old, never
| mind a billion years old.
| rflrob wrote:
| How "old" is a single-celled organism? I don't know the precise
| details for Cyanobacteria, but it could be a relatively equal
| split (unlike budding, a perfectly reasonable alternative). In
| that case, are both offspring of a cell division the age of the
| "parent"? If so, why stop at the time since one generation?
| "But wait", you may complain, "they are constantly exchanging
| molecules with their environment!" So is the "age" of the
| organism the point at which none (or equivalently half or any
| other fraction you choose) of the atoms inside the organism
| were inside the organism previously? That implies you could
| watch a single, discrete cell not dividing, and it's "age"
| would be constantly fluctuating, not simply monotonically
| increasing. It's entirely possible that age is not a
| meaningful, well-defined concept here.
|
| But less philosophically, when people refer to "living
| fossils", they generally mean that the organisms haven't
| changed much in form or physiology in a long time. There's no
| reason to believe that they aren't subject to the same pressure
| to adapt to changing conditions via natural selection, but
| those adaptations aren't readily visible.
| cheph wrote:
| > How "old" is a single-celled organism?
|
| Good question, I looked around a bit for this, it seems the
| life of a single celled organism is taken to be from division
| to the next division, but really this is a bit odd, because
| nothing died there. Clearly age for such organisms is not a
| well defined concept.
| mytailorisrich wrote:
| They are not claiming that those very organisms have been alive
| for that long (the title is poorly worded).
|
| The point they are making is that stromatolites have existed
| for billions of years according to the fossil records.
| cheph wrote:
| My complaint is exclusively with the title, not the article,
| which I don't think supports the claim in the title.
| taneq wrote:
| I've always wondered the same. They're only an organism in the
| same sense that a reef is an organism.
| NelsonMinar wrote:
| I was frustrated that article didn't have pictures. Here's a nice
| gallery:
| https://www.gettyimages.com/photos/stromatolite?phrase=strom...
| pseudolus wrote:
| There was some publicized and disputed research that emerged a
| few years ago that dated the emergence of certain stromatolites
| in Greenland to 3.7 billion years ago. However, a certain
| consensus has emerged that the structures are not the remnants of
| stromatolites but rather just rock structures [0][1].
|
| [0] https://astrobiology.nasa.gov/news/on-the-ground-in-
| greenlan....
|
| [1] https://www.nationalgeographic.com/science/2018/10/news-
| olde...
| vikramkr wrote:
| Building up oxygen being something that gave the "kiss of life"
| is an interesting perspective, considering that oxygenation was
| responsible for one of the largest mass extinctions ever
| Razengan wrote:
| Don't you know, life needs oxygen, anything else isn't life.
|
| (A jab at searches for extraterrestrial life that maintain
| oxygen as a key criteria)
| gameswithgo wrote:
| Its a waste product or a necessity so either way its a
| chemical signature to look for.
| Razengan wrote:
| Do our robots use or emit oxygen?
| harperlee wrote:
| Coupled with the infrastructure that feeds them the
| energy they need: they consume it in CO2 emissions.
| cheph wrote:
| > (A jab at searches for extraterrestrial life that maintain
| oxygen as a key criteria)
|
| I am not aware of any searches that have oxygen as a
| necessary condition for life and I doubt they exist.
|
| It is not even considered a very good biosignature[1][2]
| because there are potential abiotic process that can
| replenish it, but it can be used as a biosignature, but that
| would work for life even if the life does not use oxygen, so
| using oxygen as a biosignature is not saying that life needs
| oxygen.
|
| [1]:
| https://en.wikipedia.org/wiki/Biosignature#False_positives
| [2]:
| https://www.liebertpub.com/doi/full/10.1089/ast.2017.1727
| SideburnsOfDoom wrote:
| > life needs oxygen, anything else isn't life.
|
| No. "An anaerobic organism or anaerobe is any organism that
| does not require oxygen for growth."
|
| https://en.wikipedia.org/wiki/Anaerobic_organism
|
| FYI, yeast for bread or beer is anaerobic.
| ceejayoz wrote:
| The poster is sarcastically pointing out the fact that a
| lot of our current SETI searching revolves around
| assumptions like "extraterrestrial life will have the same
| chemical basis as Earth life does". Like needing oxygen.
| bpodgursky wrote:
| I mean SETI is literally looking for radio signals so
| this doesn't track at all.
|
| A lot of astronomy is looking for familiar chemical
| signatures yes, but it's more in the vein of "looking for
| chemicals which could not, to our knowledge, have been
| produced through natural processes". Which is not
| unreasonable IMO.
| Voloskaya wrote:
| You are completly mischaracterizing it.
|
| No one assumes that ET life will necessarily be similar
| to life as we know it on earth, but we know life like we
| know it is possible, and we know what to look for to
| detect it, so it is certainly much easier than just
| trying to detect "something else", it's hard to find
| something when you don't know what you are looking for.
| ceejayoz wrote:
| On the flipside, looking _only_ for Earth-like life -
| like focusing on the "habitable zone" - may be extremely
| limiting.
|
| Europa, for example, isn't in said zone.
| Voloskaya wrote:
| The issue isn't a lack of candidates though, we have too
| much data to analyse, so it's about filtering not
| expanding the field of search.
| SideburnsOfDoom wrote:
| > The poster is sarcastically pointing out
|
| Maybe. If so, the poster is playing stupid games, and
| winning stupid prizes. We can't be sure - imitation
| stupidity is functionally equivalent to the real thing
|
| > SETI
|
| Search for Extra-Terrestrial Intelligence
|
| Intelligence, not life. Radio-astronomy not microbes.
| Poster is not successfully talking about SETI in any way,
| sarcastic or not. Why they would attempt to do so in
| response to an article about Cyanobacteria is a mystery.
|
| tl;dr: As attempts to communicate go, it lacks many
| things.
| andai wrote:
| I think you missed the sarcasm.
| SideburnsOfDoom wrote:
| I think people's statements should generally be taken at
| face value.
| novaRom wrote:
| Strictly speaking every living thing needs oxygen atoms
| (for example from water), because they are a necessary
| constituent of the RNA/DNA machinery.
| ceejayoz wrote:
| Every living thing _on Earth_.
|
| The point they're making is that life _off_ Earth might
| not use DNA /RNA at all.
| codecamper wrote:
| blue green algae aka cyanobacteria.
|
| They also may be the solution for quickly turning back global
| warming.
|
| George Church says that altering cyanobacteria dna to protect
| them from their natural viral enemy, the Cyanophage, could allow
| them to proliferate and they would then pull co2 out of the air,
| and after mostly sink to the bottom of the oceans.
|
| Not entirely sure how he imagines controlling it all, but it is
| an interesting & out of the box idea.
| peter303 wrote:
| Chemotrophs probably existed before photosynthesis. The latter is
| a rather complex sequence of enzymes and took a while to evolve.
|
| Chemotrophs hijack natural rock chemistry reactions. Most likely
| it was the weathering of fresh, hot basalt at underseas volcanos.
| Some of these metabolic pathways require no enzymes to proceed.
| Then enzymes would evolve to allow such life to expand into less
| opportunistic environments.
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