Allan C. Wilson studied genes, proteins, and body structures of animals and humans in the US during the second half of the twentieth century. Wilson also studied human evolution. Although morphology and behaviors of humans (Homo sapiens) and great apes differ, Wilson found that they have biochemical and genetic similarities. Wilson and his colleagues calculated the time period of humans' and African apes' common ancestor. Wilson and his team also studied DNA outside of the nucleus in the cellular energy producing particles, called mitochondrial DNA (mtDNA), to study when different human groups evolved from each other.

Oliver Smithies researched physical chemistry, biochemistry, and genetics in England, Canada, and the United States during the twentieth and early twenty-first centuries and contributed to the study of gene function. During the 1950s, Smithies developed a technique to improve separating proteins based on their physical properties. Later, in the 1980s, Smithies utilized homologous recombination, a process that involves two similar pieces of deoxyribonucleic acid, or DNA, that exchange information, to target and manipulate specific genes. Smithies’s research on homologous recombination helped lead to the creation of the knockout mouse, a model organism that has genetic alterations to a single gene, to help researchers understand the function of genes in development. In 2007, Smithies received the Nobel Prize in Physiology or Medicine along with Sir Martin Evans and Mario Capecchi for work on introducing specific gene modifications in mice. Smithies’s scientific contributions toward developing the knockout mouse provided a basis for subsequent research studying the impact of different genes on human health.