What is really the oldest multicellular life we've found so far?

[Faelrin]

Like I just learned about the Francevillian biota from a reddit thread, and I'm surprised I've never heard of it before. It's potentially multicellular life much older then the Ediacaran biota. Like over 2.1 billions years old from the Paleoproterozoic Era, and around prior to the Great Oxidation Event, or I guess as I've read about it before, the snowball Earth extinction event. I've actually known about this extinction event much longer, but again didn't even know about the Francevillian biota until now. Now what I'm confused about is that there was this find back in 2021 (Bicellum brasieri) that was in the news because of it possibly being the oldest multicellular life found. But if the Francevillian biota is multicellular life, then wouldn't those be the oldest multicellular life? I'm a bit confused on all of this. What's the current consensus? I guess I should probably look for some papers on this stuff, unless anyone can point me to any.

Here's some examples of the Francevillian biota (I rather like the sunny side egg shaped A and B ones):



Bicellum brasieri:

[Stegotyranno420]

Our common ancestor with all other humans, all dinosaurs, mushrooms, and a bannana likley/possibly looked like this. It is an amazing thought, somewhat wholesome(?).
Praise to our great great great ^2000 grandparent!

[Crackington]

It's mind-blowing isn't it?

Thanks for posting the photos @Faelrin. I must say Francevillian E reminds me of the Martian "fossil bacteria" picture from a few years back!

[dinofelid]

Really interesting, I hadn't heard about these! In terms of the astrobiological question of whether the path to complex multicellular life might involve some "hard steps" that would only occur on a small fraction of planets with suitable conditions for life, if these organisms were really an independent evolution of multicellularity, that might suggest it's not a hard step, although it might involve some preconditions (like the evolution from prokaryote-style cells to eukaryote-style ones, or the evolution of photosynthesis or sexual reproduction) that could themselves be rare.

Now what I'm confused about is that there was this find back in 2021 (Bicellum brasieri) that was in the news because of it possibly being the oldest multicellular life found. But if the Francevillian biota is multicellular life, then wouldn't those be the oldest multicellular life?

This article on Bicellum brasieri quotes one of the researchers who made the find saying "Our fossil shows life-cycle stages with two different kinds of cells, which could be the first step toward the evolution of complex multicellularity in the evolutionary lineage leading to the Metazoa." So, probably the difference is that it's thought the Francevillian biota are not ancestors of the current Metazoan group, but are an independent development of multicellularity that went extinct. The "Fate" section of the wikipedia article on the Francevillian biota says "The biota formed with the Great Oxidation Event, a temporary increase in atmospheric oxygen, and became extinct from marine anoxia when the event was terminated by the drop in oxygen levels of the Lomagundi event", citing this paper, which says:

Their absence from the later fossil record might ultimately be related to the fall in the atmospheric oxygen level that followed the ca. 2.22-2.1 Ga Lomagundi carbon isotope excursion [18], [59]–[63], followed by a long-lived and extensive marine anoxia that forms the hallmark for the most of the Proterozoic Era after ca. 2.1 Ga [59], [18]. Oxygen content in surface environments is not universally accepted as a major driver for the evolution and complexification of multicellular life [64], [65]. However, the emergence and later disappearance of megascopic life in association with oxygen overshoot and fall in the early Paleoproterozoic Eon [18], [59]–[63] is consistent with oxygen availability as a driver of evolutionary adaptation [39], [66], including aspects of body size [67].

[Faelrin]

So here's a new paper about the Francevillian sub-basin and if it could have supported life (paywalled):

https://www.sciencedirect.com/science/article/abs/pii/S0301926824001669

Article about the paper (and some background on the formation):

https://www.bbc.com/news/articles/c3geyvpxpeyo

Some wonderful art from Abderrazzak El Albani interpreting the weird structures found there as once living organisms:

[ceratopsian]

I caught this on the BBC this morning. Fascinating, though I lack the required knowledge to start evaluating the data and its interpretation.