On the evolution of cells

Abstract

A theory for the evolution of cellular organization is presented. The model is based on the (data supported) conjecture that the dynamic of horizontal gene transfer (HGT) is primarily determined by the organization of the recipient cell. Aboriginal cell designs are taken to be simple and loosely organized enough that all cellular componentry can be altered and͞or displaced through HGT, making HGT the principal driving force in early cellular evolution. Primitive cells did not carry a stable organismal genealogical trace. Primitive cellular evolution is basically communal. The high level of novelty required to evolve cell designs is a product of communal invention, of the universal HGT field, not intralineage variation. It is the community as a whole, the ecosystem, which evolves. The individual cell designs that evolved in this way are nevertheless fundamentally distinct, because the initial conditions in each case are somewhat different. As a cell design becomes more complex and interconnected a critical point is reached where a more integrated cellular organization emerges, and vertically generated novelty can and does assume greater importance. This critical point is called the ''Darwinian Threshold'' for the reasons given.

How life changes itself: The Read–Write (RW) genome

“…Based on ribosomal RNA taxonomy [105], we know today that symbiogenesis was responsible for two of the most important events in all of evolutionary history: (a) Incorporation of an alpha-proteobacterium as the mitochondrion in the ancestor of all eukaryotic cells [106]. (b) Incorporation of a cyanobacterium as the plastid in the ancestor of photosynthetic eukaryotes [107].…”

An evolutionary framework for cultural change: Selectionism versus communal exchange

“…Because of phenomena such as mutualism, lineage reticulation (due to horizontal gene transfer and allopolyploidy-the combining the genomes of different parental species), certain traits evolve with astonishing speed, thereby diminishing the continuity and distinctiveness of species [53,143]. Indeed, the stability of genetic information is so compromised that sequencing three Escherichia coli genomes revealed that fewer than 40% of the genes were common to all three [138].…”

“…Research into the origin of life is stymied by the improbability of a spontaneously generated structure that replicates using a self-assembly code (such as the genetic code). This has led to widespread support for the hypothesis that the earliest protocells were not self-replicating automata but autocatalytic molecular networks that evolved (albeit haphazardly) through a nonDarwinian process involving horizontal (lateral) transfer of innovation protocols [36,73,91,105,131,133,143]. This process (illustrated schematically in Fig.…”

An archaeal origin of eukaryotes supports only two primary domains of life

“…Although similar to Bacteria in terms of cell structure, molecular phylogenies for ribosomal RNA and a small core of genes, that mainly have essential roles in protein translation 3 , suggested that the Archaea were more closely related to the eukaryotic nuclear lineage; that is, to the host cell that acquired the mitochondrion 4 . The idea that Archaea and eukaryotes are more closely related to each other than either is to Bacteria depends on analyses suggesting that the root of the tree should be placed on the bacterial stem, or within the Bacteria [5][6][7][8][9][10][11][12] , implying that the prokaryotes-cells that lack a nucleus-are a paraphyletic group 13 .…”