Even in their quietest and stillest moments, forests are places of fierce competition. Sunlight is the one of the most precious commodities here, and plants jostle, circumvent, and kill each other for prime positions beneath the incoming rays. Ferns are masters of this game; they excel at growing in the shade. Fay-Wei Li from Duke University thinks that their success depends on a single moment that happened around 180 million years ago, when an ancient fern stole a gene from another plant.

Ferns are sometimes portrayed as relics of an earlier phase of plant evolution, which were outcompeted by flowering plants and relegated to the bottoms of forests. But that’s not the case. Ferns may be an ancient group (they