The first animals
Somewhere in the Tonian ocean, cells stop living alone and become a single body.
- When
- Known to
- ± 100 million years
- Era
- Neoproterozoic, Proterozoic
Molecular clocks place the origin of animals around 800 million years ago, several hundred million years before any unambiguous animal fossil. The earliest were probably sponge-like filter feeders, and their bodies would leave almost nothing recognisable behind. The long gap between the genetic origin and the fossil record — the 'molecular clock problem' — remains one of palaeontology's sharpest disagreements.