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.
What happened to him next in his career?
Lewontin later introduced the D' measure of linkage disequilibrium.
(He also introduced the term "linkage disequilibrium", about which many population geneticists have been unenthusiastic.
Did he publish any more of his research?
Lewontin and Hubby's paper also discussed the possible explanation.

Question: What explanation did the paper talk about?
Self-contained rewrite: What explanation did Richard Lewontin and Hubby's paper talk about?