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Project Progress

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Timescale for the Evolution of Life on Earth: Molecular Evolution Approach (dm)

Studies continue on the evolution of prokaryotes and eukaryotes, with emphasis on clarifying relationships and divergence times using genomic data, and relating this to Earth history. We completed an initial study of prokaryote genomes where we discovered that many eukaryotic genes of eubacterial origin arise basally among eubacteria rather than being close to alpha-proteobacteria. The simplest explanation is that they arose through an earlier, pre-mitochondrial, symbiotic event. Our time for the origin of cyanobacteria is later than anticipated yet precedes the time period (2.4-2.0 Ga) that some believe represents the major rise in oxygen. We completed a study of fungi and land plants with a large number of nuclear protein-coding genes indicating that land was colonized much earlier (>1 Ga) than the fossil record indicates (~480 Myr ago). We proposed that this early colonization of land by eukaryotes affected the climate of the Proterozoic, possibly leading to the Neoproterozoic snowball Earth events and Cambrian explosion of animals. When compared with previous goals set, we found that productivity (discoveries) has been higher than expected, but that attempting to predict what specific topics and areas of study will yield breakthroughs is difficult. The approach we have taken is to follow the general goals of the project but to be flexible enough to direct energy towards areas showing greatest rewards at any one time.