beta-globin studies
In 1949, Linus Pauling et al. introduced electrophoresis to separate different mutants of hemoglobin, a technique that was rapidly adapted to analyze variation in other blood proteins.
References
Harding RM, Fullerton SM, Griffiths RC, Bond J, Cox MJ, Schneider JA, Moulin DS, Clegg JB. Archaic African and Asian lineages in the genetic ancestry of modern humans. Am J Hum Genet. 1997 Apr;60(4):772-89. PMID: 9106523