LIFE × EARTH

The Invention of Wood

~393 to 383 million years ago

Phanerozoic · Paleozoic · Devonian

A stiff polymer laid down around cellulose let a stem hold a column of water metres above the ground and carry its own weight while it did. Lignin is the polymer, and it is what makes wood wood. Roots followed the trunks downward: by the middle Devonian one tree, Archaeopteris, had a root system with essentially the same design as a modern seed plant's.

Why it matters

Height is what wood buys, and height is worth buying only because of shade: a plant that overtops its neighbours takes their light. That competition is why forests are tall, why they are layered, and why so much of the carbon on land sits in trunks rather than in leaves.

Dating & uncertainty

Lignin chemistry appears earlier, with the first vascular plants; what the middle Devonian adds is the tree, and with it root systems comparable to those of modern seed plants.

Sources

1. Stein et al. (2020), Current Biology · Mid-Devonian Archaeopteris roots signal revolutionary change in earliest fossil forests
2. Renault et al. (2019), Current Opinion in Biotechnology · Harnessing lignin evolution for biotechnological applications
3. Decombeix et al. (2011), Journal of the Geological Society · Transitional changes in arborescent lignophytes at the Devonian-Carboniferous boundary

Earth history as one day

21:55:202 h 5 min before midnight

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