Pre-Darwinian Evolution Before LUCA
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Pre‑Darwinian Evolution Before LUCA Shiping Tang1 Received: 5 March 2020 / Accepted: 12 July 2020 © Konrad Lorenz Institute for Evolution and Cognition Research 2020
Abstract If the coming of the last universal cellular ancestor (LUCA) marks the crossing of the “Darwinian Threshold” (Woese in Proc Natl Acad Sci USA 99:8742–8747, 2002), pre-LUCA evolution must have been pre-Darwinian. But how did pre-Darwinian evolution actually operate? Bringing together and extending insights from both earlier and more recent contributions, this essay advances three principal arguments regarding the pre-Darwinian evolution. First, in the pre-Darwinian epoch, survival essentially meant persistence within the prebiotic system, and it depended mostly on chemical variation and interaction. Second, selection operated upon four different properties: chemical; chemical-physical; vesicles’ capacities in absorbing, engulfing, and merging; and protocells’ coupling of metabolism, replication, and division. Third, division evolved from a state without tight coupling of replication with division to a state of tight coupling. Eventually, protocells with a tight coupling of replication with division became the First Universal Cellular Ancestors (FUCAs) and then LUCA. Keywords Darwinian Threshold · FUCAs · Horizontal biomolecule transfer (HBMT) · Horizontal gene transfer (HGT) · LUCA · Pre-Darwinian evolution
Introduction: Evolution Before the Darwinian Threshold The central mechanism of biological evolution, variationselection-inheritance, is one of the most universal mechanisms known. Much of our understanding of variationselection-inheritance, however, has been dominated by the gene-centric neo-Darwinian Modern Synthesis with a rather narrow understanding of what constitutes variation, selection, and inheritance. This unduly narrow understanding of variation, selection, and inheritance may have been a key cause behind our failure to adequately explain some critical puzzles in biological evolution, including the origin of the first cell. If the coming of the last universal cellular ancestor (LUCA) marks the crossing of the “Darwinian Threshold” (Woese 2002), it follows that pre-LUCA evolution must have been pre-Darwinian.1 By pre-Darwinian, I mean that evolution before the Darwinian Threshold must have operated
* Shiping Tang [email protected] 1
School of International Relations and Public Affairs (SIRPA), Fudan University, Shanghai, China
in a non-Darwinian way that eventually paved the way for Darwinian evolution after the Darwinian Threshold. But how did pre-Darwinian evolution actually operate? And if pre-Darwinian evolution did operate (cf. Tessera 2018), how can we modify variation-selection-inheritance with a pre-Darwinian logic in order to explain the origin of the first batch of protocells (or the first universal cellular ancestors, FUCAs) before they evolved into LUCA? I advance three principal arguments regarding the preDarwinian evolution, by bringing together and extending insights from earlier and more
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