Historical and Epistemological Perspectives on What Horizontal Gene Transfer Mechanisms Contribute to Our Understanding of Evolution

Abstract

Since the 1990s, results coming in from molecular phylogenetics necessitate us to recognize that Horizontal Gene Transfer (HGT) occurs massively across all three domains of life. Nonetheless, many of the mechanisms whereby genes can become transferred laterally have been known from the early twentieth century onward. The temporal discrepancy between the first historical observations of the processes, and the rather recent general acceptance of the documented data, poses an interesting epistemological conundrum: Why have incoming results on HGT been widely neglected by the general evolutionary community and what causes for a more favorable reception today? Five reasons are given: (1) HGT was first observed in the biomedical sciences and these sciences did not endorse an evolutionary epistemic stance because of the ontogeny/phylogeny divide adhered to by the founders of the Modern Synthesis.(2) Those who did entertain an evolutionary outlook associated research on HGT with a symbiotic epistemic framework. (3) That HGT occurs across all three domains of life was demonstrated by modern techniques developed in molecular biology, a field that itself awaits full integration into the general evolutionary synthesis. (4) Molecular phylogenetic studies of prokaryote evolution were originally associated with exobiology and abiogenesis, and both fields developed outside the framework provided by the Modern Synthesis. (5) Because HGT brings forth a pattern of reticulation, it contrasts the standard idea that evolution occurs solely by natural selection that brings forth a vertical, bifurcating pattern in the "tree" of life. Divided into two parts, this chapter first reviews current neo-Darwinian "tree of life" versus reticulate "web of life" polemics as they have been debated in high-profile academic journals, and secondly, the historical context of discovery of the various means whereby genes are transferred laterally is sketched. Along the way, the reader is introduced to how HGT contradicts some of the basic tenets of the neo-Darwinian paradigm.

Testing the “(Neo-)Darwinian” Principles against Reticulate Evolution: How Variation, Adaptation, Heredity and Fitness, Constraints and Affordances, Speciation, and Extinction Surpass Organisms and Species

“…During their lytic cycle [68], when bacteriophages destroy their host, they accidentally package bacterial genes from their host and transmit these to recipient bacteria upon infection [69][70][71].…”

“…Research has shown that bacterial antibiotic resistance [124] was acquired by horizontal gene transfer [71] and horizontal gene transfer has been argued to have facilitated the evolution of the major metabolic pathways that enable prokaryotes to survive [125].…”

“…Lateral gene transfer can bring back genes from the dead through processes of transformation and genomes are filled with genes of which the host (species) did not survive [71]. Lateral gene transfer might therefore be an adaptive response to extinction, by providing a lifeline to those abandoning a sinking ship, so to speak.…”

Symbiosis, History of

“…Symbiosis research also progressed from within the biomedical and bacteriological sciences where bacteria became understood as parasitic agents of disease. Ferdinand Cohn published a first systematic classification of bacteria in 1872; in 1876, Robert Koch associated the anthrax bacterium with the Anthrax disease ('Milzbrand-Krankheit') in cows; Pasteur's work on the germ theory of disease was read before the French Academy of Science in 1878; and Charles Louise Alphonse Laveran, the discoverer of the malaria parasite, was one of the first to, in 1880, recognize parasitic protozoa as causative agents of disease (Gontier, 2015b).…”

“…Beijerinck, another student of de Bary, also found Rhizobia, nitrogen-fixing, symbiotic bacteria present in the roots of legumes, and he was the first to point out their importance for agriculture (because rhizobia-rich roots and soil makes for fertile soil). Beijerinck is considered one of the founders of virology, and in nineteenth century academic circles, also de Bary (1861) was mostly known for his studies on plant diseases and for reporting on the life cycle of the fungus Phytophthora infestans that is parasitic on potatoes thereby causing potato blight (Gontier, 2015b).…”