Did something decay, evaporate, or annihilate during big bang nucleosynthesis?

Results of a detailed examination of the cascade nucleosynthesis resulting from the putative hadronic decay, evaporation, or annihilation of a primordial relic during the big bang nucleosynthesis (BBN) era are presented. It is found that injection of energetic nucleons around cosmic time ${10}^3\mathrm{s}$ may lead to an observationally favored reduction of the primordial ${}^7\mathrm{L}\mathrm{i}/\mathrm{H}$ yield by a factor 2–3. Moreover, such sources also generically predict the production of the ${}^6\mathrm{L}\mathrm{i}$ isotope with magnitude close to the as yet unexplained high ${}^6\mathrm{L}\mathrm{i}$ abundances in low-metallicity stars. The simplest of these models operates at a fractional contribution to the baryon density ${\Omega }_b{h}^2\gtrsim 0.025$, slightly larger than that inferred from standard BBN. Though further study is required, such sources, as, for example, due to the decay of the next-to-lightest supersymmetric particle into GeV gravitinos or the decay of an unstable gravitino in the TeV range of abundance ${\Omega }_{\tilde{G}}{h}^2\sim 5\times {10}^{-4}$ show promise to explain both the ${}^6\mathrm{L}\mathrm{i}$ and ${}^7\mathrm{L}\mathrm{i}$ abundances in low-metallicity stars.