title: Early evolution without a tree of life.
abstract: Life is a chemical reaction. Three major transitions in early evolution are considered without recourse to a tree of life. The origin of prokaryotes required a steady supply of energy and electrons, probably in the form of molecular hydrogen stemming from serpentinization. Microbial genome evolution is not a treelike process because of lateral gene transfer and the endosymbiotic origins of organelles. The lack of true intermediates in the prokaryote-to-eukaryote transition has a bioenergetic cause.
authors.affiliation: Institut of Botany III, University of Düsseldorf, 40225 Düsseldorf, Germany. w.martin@uni-duesseldorf.de
authors.forename: William F
authors.initials: WF
authors.lastname: Martin
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D005075:Biological Evolution; D004734:Energy Metabolism; D004777:Environment; D005057:Eukaryotic Cells / Q000737:chemistry / Q000166:cytology; D005796:Genes; D006859:Hydrogen / Q000737:chemistry; D008928:Mitochondria / Q000737:chemistry / Q000235:genetics; D000069497:Origin of Life; D010100:Oxygen / Q000737:chemistry; D010587:Phagocytosis; D010802:Phylogeny; D011387:Prokaryotic Cells / Q000737:chemistry / Q000166:cytology; D013559:Symbiosis
chemical_list: D006859:Hydrogen; D000255:Adenosine Triphosphate; D010100:Oxygen