LIFE × EVOLUTION

The First Animals on Land

~425 million years ago (clocks suggest earlier)

Phanerozoic · Paleozoic · Silurian

The oldest body fossil of an animal living out of water is a millipede, dug from the Scottish island of Kerrera and about 425 million years old. It was not a single crossing: millipedes and centipedes, insects and their kin, and spiders and their kin each made the move independently, and the gene trees make a route straight from the sea, rather than up a river, the likeliest for all three.

Why it matters

This is where land ecosystems become visible, with small arthropods eating dead plants in damp ground. How much earlier they began is the open question: molecular clocks put the myriapods ashore in the Cambrian, possibly before there were land plants to eat, and the fossils are a hundred million years younger. Early continental deposits are rare enough that the gap may be a gap in the rock.

Dating & uncertaintyDisputed

The oldest body fossil of a land animal is a millipede from Kerrera, Scotland, at about 425 Ma. Molecular clocks put the move ashore in the Cambrian or Ordovician, up to a hundred million years earlier, and the gap between the two lines of evidence is unresolved.

Sources

1. Tihelka et al. (2022), Biology · Was there a Cambrian explosion on land? The case of arthropod terrestrialization
2. Brookfield et al. (2020), Historical Biology · Myriapod divergence times differ between molecular clock and fossil evidence
3. Lozano-Fernandez et al. (2016), Philosophical Transactions of the Royal Society B · A molecular palaeobiological exploration of arthropod terrestrialization

Earth history as one day

21:45:112 h 15 min before midnight

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