Conversation so far:
What type of work was Richard involved in?
both theoretical and experimental population genetics.
What else did he accomplish?
technology.
He was the first person to do a computer simulation of the behavior of a single gene locus (previous simulation work having been of models with multiple loci).
What else was he the first to do?
he and Ken-Ichi Kojima were the first population geneticists to give the equations for change of haplotype frequencies with interacting natural selection at two loci.
What resulted from these discoveries?
the discovery of high levels of molecular variability gave population geneticists ample material to work on, and gave them access to variation at single loci.

Question: What happened to him next in his career?
Self-contained rewrite: What happened to Richard Lewontin next in his career, after discovering high levels of molecular variability?