A nice thought piece by Ford Doolittle in PLoS Genetics. We run our first year students though this each year, so it is nice to think that some of them might find and be influenced by this article next year.
What Is the Tree of Life? (2016) PLoS Genet 12(4): e1005912. doi: 10.1371/journal.pgen.1005912
A universal Tree of Life has long been a goal of molecular phylogeneticists, but reticulation at the level of genes and possibly at the levels of cells and species renders any simple interpretation of such a Tree of Life, especially as applied to prokaryotes, problematic. Lateral gene transfer is much more frequent than most biologists would have imagined up until about 20 years ago, so phylogenetic trees based on sequences of different prokaryotic genes are often different. How to tease out from such conflicting data something that might correspond to a single, universal Tree of Life becomes problematic. Moreover, since many important evolutionary transitions involve lineage fusions at one level or another, the aptness of a tree (a pattern of successive bifurcations) as a summary of life’s history is uncertain.