Fossilized eukaryotes from 2.7 billion year old shales in Tanzania
Bibliographic record
Abstract
Abstract Some of the evidence for the existence of life in the Archean Eon (4.0-2.5 Ga) comes from ‘microfossils’ that are believed to be the mineralized remnants of simple prokaryotic lifeforms. They are spheroidal shaped and a few microns to tens of microns across and most likely represent early prokaryotic organisms. Here we describe spheroidal carbon structures that reach sizes of up to 540 microns from the 2.72 billion years ago (Ga) carbonaceous shales from the Lower Nyanzian Formation in the Geita Greenstone Belt of Tanzania. They are interpreted as microfossils based on their multi-chambered structures with pentagonal to hexagonal sectional geometries or floral forms, and chambers connected by regularly placed, tube-like structures that also connect inner chambers to the outside. The carbonaceous material in the walls is partly composed of disorganised kerogenous carbon with δ13C values averaging -44.6‰ that forms membranes coating a denser core of hematite enriched in P and transition metals (Zn, Cu, Ca). The fossils meet all criteria for syngeneity and biogenicity. Whether these structures are remnants of gigantic bacteria or early eukaryotes such as a testate rhizarian is unclear but they appear to represent a relatively complex organism that lived in a shallow, volcanically-dominated, marine environment where oxygen was locally available.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".