A pretty small effect, given that Earth has on net lost atmosphere over time there was less cosmic ray radiation on the surface back then then there is now. Wh

A pretty small effect, given that Earth has on net lost atmosphere over time there was less cosmic ray radiation on the surface back then then there is now. Which is in stark contrast to UV radiation which came in easily before the Great Oxygenation produced an ozone layer. LUCA, the last universal common ancestor, probably already had some oxygen resistance before then because UV radiation was always breaking up water molecules to produce tiny amounts of oxygen that it had to deal with. (Currently reading Oxygen by Nick Lane)