LIFE × EVOLUTION

The Oldest Organism We Can Put a Name To

~1.05 billion years ago

Proterozoic · Mesoproterozoic · Stenian

A tuft of branching filaments, fossilised in Arctic Canada, is the oldest organism that can be placed in a group still alive today: Bangiomorpha, a red alga. It does three things at once that nothing older is known to do. Its cells are not alike: a holdfast anchors it and filaments rise from that, so they have specialised and can no longer live apart. It runs photosynthesis inside a complex cell, which means the chloroplast had already been acquired. And it makes spores of two distinct kinds, which is to say it has sex.

Why it matters

Cells that stick together make a colony; cells that specialise and depend on one another make an organism. Bangiomorpha is the oldest one we can name, and its date matters beyond itself: because we know where a red alga sits on the tree, its age calibrates the clock for everything below it. Re-dating it in 2017 moved that calibration by 150 million years.

Dating & uncertainty

Bangiomorpha is the oldest multicellular eukaryote we can assign to a modern group, which is not the same as the oldest multicellular organism: colonial forms such as Horodyskia are reported from Tonian rocks, and simple multicellular fossils go back to about 1.6 billion years. Its own age was revised, from the long-accepted 1.2 billion to 1.047 billion, by rhenium-osmium dating of the beds above and below it.

Sources

1. Gibson et al. (2017), Geology · Precise age of Bangiomorpha pubescens dates the origin of eukaryotic photosynthesis
2. Butterfield (2000), Paleobiology · Bangiomorpha pubescens n. gen., n. sp.: implications for the evolution of sex, multicellularity, and the Mesoproterozoic/Neoproterozoic radiation of eukaryotes
3. Li et al. (2023), Communications Biology · Tonian carbonaceous compressions indicate that Horodyskia is one of the oldest multicellular and coenocytic macro-organisms
4. Sánchez-Baracaldo et al. (2017), PNAS · Early photosynthetic eukaryotes inhabited low-salinity habitats

Earth history as one day

18:26:575 h 33 min before midnight

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