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Project Progress

Our research involves molecular clocks and phylogenetics to better understand the relationship between planetary history and the evolution of life. We made progress in theoretical and empirical studies during the past year. In the former area we developed a robust method for estimation of the mode, and tested it with computer simulations (Hedges and Shah, 2003). Such a method is useful for any data, but our immediate use was with molecular clock analyses. We also developed a method for phylogenetic analysis of complete genome sequences (Blair and Hedges, ms). In another paper, I developed a biological trigger model for snowball Earth events (Hedges, 2003).

Our empirical work involved eukaryote and prokaryote studies. We sampled all available protein sequences in the public databases (20-200 genes per node) to develop a tree and timescale of eukaryotes. With that framework we showed that complexity (as measured by cell types) has increased much earlier than previously believed (Hedges et al., 2004). In another study using similar methods we determined time estimates for the colonization of land by metazoans in the late Precambrian (Pisani et al., 2004). Our prokaryote genome work resulted in a detection of early horizontal gene transfer events (Thomarat and Hedges, ms), a more robust timescale for prokaryote evolution, and better constraints on the origin of organisms producing metabolic products that influenced the history of the biosphere (Battistuzzi and Hedges, ms).