Discovery of the oldest evidence of motility on Earth

February 11, 2019, CNRS
Previously, the oldest traces of this kind found dated to approximately 600 million years ago: the Ediacaran period, also characterized by a peak in dioxygen and a proliferation in biodiversity. Scale bar: 1 cm. Credit: A. El Albani / IC2MP / CNRS - Université de Poitiers

An international multi-disciplinary team coordinated by Abderrazak El Albani at the Institut de chimie des milieux et matériaux de Poitiers (CNRS/Université de Poitiers) has uncovered the oldest fossilised traces of motility. Whereas previous remnants were dated to 570 million years ago, this new evidence is 2.1 billion years old. The fossils were discovered in a deposit in Gabon, where the oldest multicellular organisms were found. The results appear in the 11 February 2019 edition of PNAS.

A few years ago, geologist Abderrazak El Albani and his team at the Institut de chimie des milieux et matériaux de Poitiers (CNRS/Université de Poitiers) discovered the oldest existing fossils of multicellular organisms in a deposit in Gabon. Located in the Franceville Basin, the deposit allowed scientists to re-date the appearance of on Earth to 2.1 billion years—approximately 1.5 billion years earlier than previously thought (600 million). At the time, the researchers showed that this rich biodiversity co-occurred with a peak in dioxygenation of the atmosphere, and developed in a calm and shallow marine environment.

In this same geological deposit, the team has now uncovered the existence of fossilised traces of motility. This shows that certain multicellular organisms in this primitive marine ecosystem were sophisticated enough to move through its mud, rich in organic matter.

The traces were analysed and reconstructed in 3-D using X-ray computed micro-tomography, a non-destructive imaging technique. The more or less sinuous structures are tubular, of a generally consistent diameter of a few millimetres, and run through fine layers of sedimentary rock. Geometrical and reveals that they are biological in origin and appeared at the same time the sediment was deposited.

Microtomographical reconstruction with a transparent view of internal structures, and a sequence of virtual cross-sections of the sample. Credit: © A. El Albani & A. Mazurier / IC2MP / CNRS - Université de Poitiers

The traces are located next to fossilised microbial biofilms, which formed carpets between the superficial sedimentary layers. It is plausible that the organisms behind this phenomenon moved in search of nutritive elements and the dioxygen, both produced by cyanobacteria.

What did these living elements look like? Though difficult to know for certain, they may have been similar to colonial amoebae, which cluster together when resources become scarce, forming a type of slug, which moves in search of a more favourable environment.

The tubes are filled with pyrite crystals (generated by the transformation by bacteria of biological tissue) found in layers of clay minerals. Parallel horizontal layers are fossilized microbial mats. Credit: © A. El Albani & A. Mazurier / IC2MP / CNRS - Université de Poitiers

Until now, the oldest traces of recognised movement were dated to 570 million years ago, an estimate that appeared to be confirmed by the molecular clock. Evidence of found in rock that is 2.1 billion years old raises new questions regarding the history of life—was this biological innovation the prelude to more perfected forms of movement, or an experiment cut short by the drastic drop in atmospheric oxygen rates that occurred approximately 2.083 billion years ago?

Explore further: Oldest biodiversity found in Gabonese marine ecosystem

More information: Abderrazak El Albani el al., "Organism motility in an oxygenated shallow-marine environment 2.1 billion years ago," PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1815721116

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torbjorn_b_g_larsson
5 / 5 (1) Feb 12, 2019
While current data admit a 2.5 Gyrs old eukaryote ancestor split, it would somewhat stress the mitochondrial symbiosis date with its current credibility range at 2 Gyrs [ https://www.natur...8-0644-x ]. The suggestion of Dictyostelium analogs is innovative though [ https://en.wikipe...scoideum ].

But trace fossils are hard to qualify due to geological confounds, IIRC the only current admitted trace pores are bacterial etches in volcanic glass who has no confounds. And of course the very long age jump between analogs is a problem for the hypothesis.

I guess we will have to wait and see how the experts on such fossils react, but I suspect this will be put on the "perhaps, but not likely" pile.
torbjorn_b_g_larsson
5 / 5 (1) Feb 12, 2019
Oh, the very next article suggest the verdict is in [ https://www.scien...ts-claim].

I won't link to the original source of the criticism, since it is a credulous pop science magazine that no one should read. But the first link discuss how the 1st author is exploring a fossil site that he wants to claim is evidence for multicellularity. And here the expert verdict:

"But Nicholas Butterfield of the University of Cambridge is sceptical about the team's new interpretations. "It's such an extraordinary claim," he says. "But they don't give compelling data to support it.""

Butterfield is doing research in the early diversification of eukaryotes [ https://www.esc.c...terfield ].
Osiris1
not rated yet Feb 12, 2019
Looks a bit like that Mars rock that was found here and claimed to be from Mars eons ago

frogman
1 / 5 (1) Feb 12, 2019
HOw can you write this without mentioning the body of knowledge related to mitochondria being bacteria = symbiosis theory? While I"m at it, mitochondrial electron transport , imported via bacteria, is a quantum computer. What, you thought that cells can regulate ten thousand biochemicals in real time without a computer?
torbjorn_b_g_larsson
not rated yet Feb 14, 2019
HOw can you write this without mentioning the body of knowledge related to mitochondria being bacteria = symbiosis theory? While I"m at it, mitochondrial electron transport , imported via bacteria, is a quantum computer. What, you thought that cells can regulate ten thousand biochemicals in real time without a computer?


I have to guess, since I am the only one mentioning mitochondria, that I am "you". The rest of the comment is jumbled up as well, likely because the meaningless mentioning of computer implies the comment is supposed to express magic beliefs instead of being based on the observed evolutionary science described in the article. (Speaking of which, what "computer" would not use its programs for 2 billion years, then suddenly do? Besides that we now know magic does not exist, claims involving it are so ludicrous.)

E.g. the evolutionary root of mitochondria was not relevant to the dating (but is described in my reference, FWIW).

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