Fossil leaf, Glossopteris sp.
Ellsworth Mountain, West Antarctica
Courtesy Science Museum of Minnesota
A blustery autumn afternoon. A small tree grows alongside a river in a warm, humid forest. A gust of wind knocks a tongue-shaped leaf into the flowing water, which buries it under mud and silt.
Time passes. A thousand floods bury the leaf deeper and deeper. The silt compresses into mudstone. Two hundred fifty million years later, geologists uncover the rock—in western Antarctica. Clearly, the continent was once a much warmer place. It was also in a different place—similar leaves in South America, Africa and India indicate that these lands were once joined.
The leaf is unlike any known today. Yet the pattern of veins resembles that of modern flowering plants, meaning this may be the ancestor of every rose petal and rice paddy, every field of grass and grove of maple on Earth.
A simple dull brown rock. Yet it contains within it the history of the world.