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Early evolution without a tree of life

DOI: 10.1186/1745-6150-6-36

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This article was reviewed by Dan Graur, W. Ford Doolittle, Eugene V. Koonin and Christophe Malaterre.Biology currently lacks a robust and comprehensive description of early evolution. We should aim to fill that void, but in a language that operates with biology and chemistry, not with branching patterns in phylogenetic trees, versions of which based on informational genes are called the tree of life. Genomes attest unequivocally to the abundance of lateral gene transfer in microbial chromosome history, but current thinking on early evolution is still largely couched in the conceptual framework of trees. When it comes to getting a fuller grasp of microbial evolution, trees might be standing in the way more than they are actually helping us at the moment, because i) the overall relatedness of prokaryotic genomes is not properly described by any single tree, and ii) the relationship of eukaryotes to prokaryotes is also not tree-like in nature because the endosymbiotic origins of organelles introduces lineage mergers and genetic amalgamation into the evolutionary process. If we aim to deliver to science and society a complete picture of early evolution, then at some point we have to incorporate the origin of life into the larger picture of things, too, which means linking microbial evolution to the elements on early Earth. Overall those are fairly tall orders, but we have to start somewhere.Getting a better picture of early evolution is important for understanding our place in the larger scheme of things. Yet the further back we look in time, the less we know about the course of life's history. The evolutionary history of organisms visible to the naked eye -- plants and animals -- has a recurrently branching phylogeny that can be more or less accurately represented in the mathematical image of a bifurcating tree. Darwin's mechanisms of natural variation and natural selection were inferred from observations of macroscopic life, and those two mechanisms are still sufficie

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