LIFE

The First Large Organisms, Perhaps

~2.1 billion years ago (biological origin disputed)

Proterozoic · Paleoproterozoic · Rhyacian

Flattened, flexible sheets up to twelve centimetres across, most with a radiating internal pattern, lie preserved in fool's gold, in Gabonese black shales laid down just after the first oxygenation of the air. The rocks and their age are not in question; the shapes are. If they are organisms, they were coordinating their growth across many cells; if they are not, chemistry here learned to draw things that look uncannily like bodies.

Why it matters

It would place complex, cooperating life a billion and a half years before the Cambrian explosion, which is exactly why it is contested.

Dating & uncertaintyDisputed

Centimetre-sized pyritised shapes in the Francevillian rocks of Gabon are read as colonies of organisms growing in a coordinated way, well before macroscopic life diversifies anywhere else in the record. No one disputes the rocks or their age; whether the shapes are bodies or mineral growths remains open. The oxygen around them is deduced from geochemistry and may have been local rather than global: the microbial mats found with them could have made their own, and probably helped preserve them too.

Sources

1. El Albani et al. (2010), Nature · Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago
2. Aubineau et al. (2018), Geobiology · Unusual microbial mat-related structural diversity 2.1 billion years ago and implications for the Francevillian biota
3. Ikouanga et al. (2023), Precambrian Research · Taphonomy of early life (2.1 Ga) in the Francevillian basin, Gabon

Earth history as one day

12:53:5511 h 6 min before midnight

if Earth’s 4.54 billion years were compressed into a single day