A long-standing hypothesis that high atmospheric oxygen levels allowed giant insects like two-foot-long dragonflies to exist in the Paleozoic era, and that their decline was due to dropping oxygen, has been challenged. New research suggests the insect tracheal breathing system's limitations, not just oxygen concentration, likely constrained their size. This reopens the question of what truly limited prehistoric insect gigantism.
Background
For decades, the dominant 'oxygen constraint hypothesis' explained the gigantism of Paleozoic insects (like Meganeuropsis with a 70cm wingspan) and their subsequent disappearance by linking size limits to historical atmospheric oxygen levels.
- Source
- Ars Technica
- Published
- Mar 28, 2026 at 08:30 PM
- Score
- 6.0 / 10