Penn State: Window to the past: New microfossils suggest earlier rise in complex life

[OKIsItJustMe]

Window to the past: New microfossils suggest earlier rise in complex life

NOVEMBER 7, 2023 By Matthew Carroll

UNIVERSITY PARK, Pa. – Microfossils from Western Australia may capture a jump in the complexity of life that coincided with the rise of oxygen in Earth’s atmosphere and oceans, according to an international team of scientists.

The findings, published in the journal Geobiology, provide a rare window into the Great Oxidation Event, a time roughly 2.4 billion years ago when the oxygen concentration increased on Earth, fundamentally changing the planet’s surface. The event is thought to have triggered a mass extinction and opened the door for the development of more complex life, but little direct evidence had existed in the fossil record before the discovery of the new microfossils, the scientists said.

“What we show is the first direct evidence linking the changing environment during the Great Oxidation Event with an increase in the complexity of life,” said corresponding author Erica Barlow, an affiliate research professor in the Department of Geosciences at Penn State. “This is something that’s been hypothesized, but there’s just such little fossil record that we haven’t been able to test it.”

When compared to modern organisms, the microfossils more closely resembled a type of algae than simpler prokaryotic life — organisms like bacteria, for example — that existed prior to the Great Oxidation Event, the scientists said. Algae, along with all other plants and animals, are eukaryotes, more complex life whose cells have a membrane-bound nucleus.

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[eppur_se_muova]

1. Nice photos of lovely cherts at the link, but no photomicrographs of the fossils in question. nt

[OKIsItJustMe]

2. Microfossil images available at linked publication

https://doi.org/10.1111/gbi.12576

Figure 1
Archetypal large spherical aggregate (SA) microfossils with wide, kerogen-free surrounding rinds. Microfossil shape is most commonly spherical, with radial symmetry. All images are vertical cross sections through bedding. (a) Plane polarised light (PPL) image of slightly ellipsoidal SAs oriented with long axes perpendicular to bedding; note the even width of rinds. Dense, bedded organic matter (OM) that directly underlies the left SA appears to be deflected downwards, around the SA and its surrounding rind (arrow). (b, c) and (d, e) show specimens in both PPL and cross polarised light (XPL), highlighting the very fine microquartz grainsize within the rinds (arrow in e). Carbonate rhombs are occasionally observed intruding into microfossil rinds; these are visible in a (left SA, right side of rind), in b, c (left side of rind), and in e (right side of rind).

(Follow above link for more Figures.)

[eppur_se_muova]

3. Thanks! The photos are not that impressive, but the oldest microfossils seldom are.

However, the accompanying text reads almost like a legal argument, as they attempt to establish the validity of the evidence and rule out alternative interpretations. This must have been a very hard paper to write -- no wonder it took five authors, to cover such disparate lines of evidence.

The idea that any organic matter has survived that long is kind of mind-blowing.