During long portions of the past 2.4 billion years, the Earth may have been more inhospitable to life than scientists previously thought, according to new computer simulations.

Using a state-of-the-art climate model, researchers now believe the level of ultraviolet (UV) radiation reaching the Earth’s surface could have been underestimated, with UV levels being up to ten times higher.

UV radiation is emitted by the sun and can damage and destroy biologically important molecules such as proteins.