The seminal experiment that illustrated the ability of genetic information to flow between species slipped by largely unnoticed. In 1959, Tomoichiro Akiba and Kunitaro Ochia discovered antibiotic resistance plasmids. The most surprising attribute of this new class of plasmids was that they carried resistance genes to multiple antibiotics and that they moved among different bacterial species, spreading resistance genes, and thereby demonstrating that genetic information can flow from one species to another (Akibaetal., 1960; Ochia et al., 1959). The implications of this finding would have profound effects ranging from the applied field of genetic engineering to the very theory of evolution. Early papers probing the deeper theoretical implications of horizontal gene transfer began to appear in the 1970s, though they were not widely acknowledged or accepted. Fritz Went, in 1971, wrote a review on similar traits that are shared by unrelated flowering plants thereby illustrating many examples of parallel evolution. In addition, he noted that the traits are shared among plants that occupied the same ecosystems. In this context he proposed that these unrelated plants were exchanging genes. He cited bacterial plasmid transfer as a precedent for such events. Krassilov in 1977 arrived at a similar model for flowering plant evolution based on his paleontological studies of the emergence of angiosperms in the fossil record. Andersonin1970andReanneyin1976suggested that horizontal gene transfer could affect evolution in the animal kingdom, and Hartman, in 1976, suggested that horizontal gene transfer might effect speciation. There were a series of theoretical papers that cited horizontal gene
transfer as an explanation for the widespread occurrence of parallelisms in the fossil record (Krassilov, 1977; Erwin and Valentine, 1984; Reanney, 1976; Jeppsson, 1984; Syvanen, 1985). Meanwhile, genetic engineering experiments began to produce startling results. In 1976, Struhl et al. placed DNA from yeast into a histidine deficient mutant of Escherichiacoli that resulted in the restoration of histidine biosynthesis. This DNA contained a histidine biosynthesis gene from the yeast genome. What seems commonplace today was difficult to comprehend back in 1976 – genes from a eukaryotic organism artificially introduced into a bacterium could actually function. Davies and Jimenez in 1980 showed that a bacterial neomycin phosphotransferase gene would express aminoglycoside resistance in yeast, showing that a bacterial gene could be expressed in a eukaryote.