Observational data on the early galactic abundances of the light elements lithium, beryllium and boron are combined with data related to the reionization of the intergalactic medium (IGM) in a search of processes happening in the early universe. Early massive metal-free stars (Pop III), largely held responsible for the reionization of the IGM, are proposed to have been also the injectors of the lithium-6 plateau, through their winds. In this sense the evolution of the 6Li/9Be ratio appears to be a key parameter for the history of nucleosynthesis as a monitor of the early formation of metals and their subsequent injection in high energy particles.