890M-year-old sponge fossil may be the earliest animal yet found | Hacker News Reader

890M-year-old sponge fossil may be the earliest animal yet found

nationalgeographic.com

86 pointsisaacfrond36 comments

I was going to note this (first learnt about it in Capra's "Web of Life", IIRC), but they did already:

>Abiotic, or nonliving, chemical processes can also form structures that look surprisingly similar to life, adds Rachel Wood, a carbonate geologist at the University of Edinburgh. "She [Turner] may be right. But I think you really have to explore and disprove all the other possibilities to make such a really strong claim like this." So for now, Wood says, "I don't think that she's really nailed that these are sponges."

>Only further analysis can resolve the debate. Wood notes that crafting three-dimensional models of the tube network would help give a more detailed look at the structures. And Riding hopes the new study will inspire more scientists to take a closer look at other stromatolites to search for more of these meshy structures.

I think about this often in relation to stromatolites[0]. The earliest evidence of life on Earth ranges from immediately after liquid water appeared on the surface to one billion years after, depending on whether or not you think the specific evidence is of abiotic origin.

That's a big range! If life appeared within a few million years of liquid water, it has huge implications for the probability of life elsewhere in the universe.

[0]: https://en.m.wikipedia.org/wiki/Stromatolite

Perhaps the assumption that there is a sharp, discernible, cutoff in the first place is incorrect?

Are there early animals we will never find because they never leave behind some sort of fossil?

Most of animals don't leave any fossils, especially without skeleton. Special conditions are required for fossilification [1].

1. https://www.americangeosciences.org/education/k5geosource/co...

The good news is that all modern fossils leave plenty of signatures in the form of legislation

Many upon many. The _vast_ majority of species are left out, and for ones that do have fossils the _vast_ majority of individuals are left out.

Something getting fossilized is basically a miracle, and us finding it is another on top.

Absolutely. Also consider that a vast portion of the Earth's crust has been recycled into the mantle over the millenia.

Maybe with enough technology we can drill into one of the sunken tectonic plates[0] and find fossils there.

[0]: https://en.wikipedia.org/wiki/Farallon_Plate#Farallon_Plate_...

Well, you can’t get fossils from rocks which have melted or metamorphised. If you try you might get lucky and find some relatively unscathed sediments, but I don’t know enough geology to say for sure how much of the plate would have escaped metamorphism.

The vast majority of extinct animal species is like that. Fossilization is an incredibly rare event.

A relatively recent discovery points to macroscopic multicellular life as early as 2.1B years ago (1), right after the Great Oxidization Event. We only have fossils of a single specie. Given the complexity of the specimens, it's unlikely to have been the only specie in existence. The rest of the biota is probably lost to time.

The fossil record for Ediacarian biota (pre-Cambrian age) is also very sparse. It's only after the evolution of endo/exoskeletons that we start to get proper fossil records

(1) - https://en.wikipedia.org/wiki/Francevillian_biota

How do we know that carbon dating is accurate for this long of time periods?

Carbon dating is only supposed to be accurate to about 40,000 years ago. They must be using some other method to date it, but I didn't see in the article where they say what method was used.

In the study linked in the article, this is written: "depositional age is known through litho- and chemostratigraphic correlation with the 892 ± 13-Ma (Re–Os black shale) Boot Inlet Formation (Shaler Supergroup (Sg)), together with other geochronological constraints"

May you please ELI5 -- I am super fascinated by this, but I cannot decipher how to to understand this sentence.

The age of the rocks it was found in.

OK, sure, makes sense. But how do they know how old the rocks are? If not by carbon dating that is...

https://www.nature.com/scitable/knowledge/library/dating-roc...

This page has a table of different dating methods that work on minerals and the time ranges to which they are accurate.

The "Re-Os" bit indicates that it was Rhenium-Osmium dating of black shale (a sedimentary rock commonly found on paleo-coastlines) in the formation.

One of the major differences between the paleontologists and archaeologists is their opinion of shale and other mudstones. Paleontologists love the stuff, archaeologists hate it.

Geologists and paleontologist usually use multiple methods to estimate age. Carbon works well for young deposits. Uranium dating can be used for much older materials. As AlotOfReading mentioned Rhenium-Osmium. Sometimes they can use Oxygen ratios in inclusions in Zircon crystals. There are other more specialized measures. Using multiple methods can help calibrate each other.

Thanks everyone, very interesting and probably worth further reading!

Here's a good podcast about it: https://www.nature.com/articles/d41586-021-02078-5

Disable javascript (easy if you're using Brave) if you want to avoid the forced email signup to read the full article.

Firefox reader mode also helps.

Downvote? Is this a browser war?

I actually upvoted.

Must have been a driveby. Cheers!

You can also enter a random email. They don't verify it.

This tends to be my preferred approach, because it degrades signal-to-noise that they get from the nag.

I go the extra mile and always enter their own email.

If you’re being malicious at that point why not just look up “software engineer companyname” on LinkedIn and use firstname.lastname@companyname.com

(Please don’t actually do this)

Haha, this is a great idea.

I don't like to enter random emails into forms. The company needlessly suffers with bad data going into their lists and ends up taxing other email providers with sends to non-existent inboxes. Unless you use a domain like example.com or something.

Use the domain of the website itself.

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