LIFE × EVOLUTION

Life Becomes Visible

~1.56 billion years ago

Proterozoic · Mesoproterozoic · Calymmian

A billion years before the Cambrian, something in the sea was already the size of a hand. Carbon films in the Gaoyuzhuang Formation of North China preserve flat, tongue-shaped bodies up to 30 centimetres long and nearly 8 wide, with outlines regular enough to sort into a few shapes rather than a jumble. Fragments broken from them show cells about ten microns across, packed edge to edge in a thick sheet: cells built into one body, not a colony of them.

Why it matters

Size on this scale is not simply more cells. It takes a body plan and a rule for growth, and something had both a billion years before animals put them to use. What these organisms were remains open; that they were large, regular and probably photosynthetic does not.

Dating & uncertainty

A volcanic ash eleven metres above the fossil bed gives 1588.8 ± 6.5 Ma, so the fossils are at least that old. Their position in the eukaryotic tree is undetermined: the cells are arranged in a sheet and the organism was probably photosynthetic, which is as far as the evidence goes.

Sources

1. Zhu et al. (2016), Nature Communications · Decimetre-scale multicellular eukaryotes from the 1.56-billion-year-old Gaoyuzhuang Formation in North China
2. Chen et al. (2024), Geological Magazine · New SIMS U-Pb zircon age on the macroscopic multicellular eukaryotes from the Gaoyuzhuang Formation
3. Chen et al. (2023), Precambrian Research · Carbonaceous macrofossils from the early Mesoproterozoic Gaoyuzhuang Formation

Earth history as one day

15:45:118 h 15 min before midnight

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