Stromatolites: A Billion-Year-Old Living Organism | Hacker News Reader

Stromatolites: A Billion-Year-Old Living Organism

bbc.com

112 pointspseudolus30 comments

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...

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.

I was frustrated that article didn't have pictures. Here's a nice gallery: https://www.gettyimages.com/photos/stromatolite?phrase=strom...

Agreed. I didn't really understand what a stromatolite was. But as soon as I saw the picture I recognised them.

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.

I've always wondered the same. They're only an organism in the same sense that a reef is an organism.

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.

My complaint is exclusively with the title, not the article, which I don't think supports the claim in the title.

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.

> 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.

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

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)

Its a waste product or a necessity so either way its a chemical signature to look for.

Do our robots use or emit oxygen?

Coupled with the infrastructure that feeds them the energy they need: they consume it in CO2 emissions.

> (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

> 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.

Strictly speaking every living thing needs oxygen atoms (for example from water), because they are a necessary constituent of the RNA/DNA machinery.

Every living thing on Earth.

The point they're making is that life off Earth might not use DNA/RNA at all.

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.

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.

> 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.

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.

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.

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.

We don’t know for a fact there is life on Europa so why would we look for exo-Europas as candidates?

We believe Europa may be habitable, which implies our definition of "habitable zone" is a bit too strict given that it tends to exclude Europa.

I think you missed the sarcasm.

I think people's statements should generally be taken at face value.

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.

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