In 1966, he and Jack Hubby published a paper that revolutionized population genetics. They used protein gel electrophoresis to survey dozens of loci in the fruit fly "Drosophila pseudoobscura", and reported that a large fraction of the loci were polymorphic, and that at the average locus there was about a 15% chance that the individual was heterozygous. (Harry Harris reported similar results for humans at about the same time.) Previous work with gel electrophoresis had been reports of variation in single loci and did not give any sense of how common variation was.