History › Complex life › Cambrian explosion
Life's move onto land
plants c. 470 million years ago; animals soon after· Event· Life & early humans
Mostly agreedGood evidence; some details, dates or numbers uncertain.
Plants, then animals, moved from water onto bare continents, starting about 470 million years ago.
See it on the History map →What happened
Before this, land was bare rock and microbial crusts. Small plants like mosses came first, helped by partnerships with fungi; millipedes, spiders and insects followed. Roots and wood came later. From roughly 395 million years ago, fish with sturdy fins, like Tiktaalik (about 375 million years ago), moved through shallows and onto land, leading to amphibians and later reptiles and mammals.
Why it matters
Plants built soil, changed the air and climate, and created the habitat in which all land animals, including humans, evolved.
How we know
Fossil plant spores about 470 million years old; fossil plants from Rhynie, Scotland; Tiktaalik, found in Arctic Canada in 2004; footprints in Poland about 395 million years old.
Still debated
Genetic clocks suggest plants may have reached land tens of millions of years before the oldest fossils, so the timing is debated.
Inside this (1)
Connections (3)
▸Great Oxidation Event built the ozone layer that allowed Life's move onto landMostly agreed
The connection
Oxygen in the air forms ozone high in the atmosphere, which blocks much of the Sun's harmful ultraviolet light. The Great Oxidation began this shield, and a later oxygen rise about 800–540 million years ago strengthened it. Without it, life on bare land would have been badly damaged.
When and how
In the upper atmosphere, building gradually over the two billion years after oxygen first rose about 2.4 billion years ago.
How sure are we?
Basic chemistry shows sunlight turns oxygen into ozone, and models tie ozone strength to oxygen levels; exactly when the shield became strong enough is less certain.
Debates and open questions
How much ozone protection early land life actually needed, and when the shield was strong enough, are debated.
▸Cambrian explosion was followed by Life's move onto landWell documented
The connection
The Cambrian explosion produced the animal groups that later moved ashore, especially arthropods (jointed-leg animals) and early vertebrates. Meanwhile green algae in fresh water gave rise to the first land plants. Within about 70 million years, plants led the way onto bare continents and animals followed.
When and how
From shallow seas and shorelines, beginning about 470 million years ago, some 70 million years after the Cambrian began.
How we know
Fossils show the order clearly: sea animals first, then land plant spores, then land arthropods and four-legged vertebrates.
Debates and open questions
Trackways suggest some arthropods ventured onto tidal flats during the Cambrian, before plants; how early animals first left water is debated.
▸Life's move onto land led to the Carboniferous coal forestsMostly agreed
The connection
Once plants evolved roots and wood, they could grow into tall trees. By the Carboniferous, giant club mosses and tree ferns formed vast swamp forests. When these plants died in waterlogged ground, they were buried before fully rotting and slowly turned into the coal mined today.
When and how
In tropical swamps of what are now North America, Europe and China, about 359–299 million years ago.
How sure are we?
Coal seams contain fossil bark, leaves and spores; repeating layers of coal and rock match known cycles of rising and falling sea level.
Debates and open questions
Whether Carboniferous conditions were unique, or such coal could form at any time given wet, sinking basins, is debated.