Recombination occurred 900 years later, producing a black-body spectrum now seen in the microwave.  
Because of the rapid temperature drop, neutrinos were no longer in thermal equilibrium with matter after one minute.  Two minutes later free protons and neutrons could combine to produce lithium and deuterium. Recombination occurred 900 years later, producing a black-body spectrum now seen in the microwave.  For ten points, name this proposed source of cosmogenesis.
Because of the rapid temperature drop, neutrinos were no longer in thermal equilibrium with matter after one minute.  
Big Bang