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Project Progress

The main goal of this research is to develop statistical methods for estimating the times of origin of major groups of organisms from molecular data as well as those of major groups of gene families and infer early evolutionary events on Earth. The most relevant work from my laboratory bearing on these questions appeared earlier this year (Glazko and Nei, 2003). In that study, we compared several methods of time estimation. We examined the effects of several factors on the estimates of divergence times and reached the following conclusions: (1) It is advisable to concatenate many gene sequences and use a multigene gamma distance for estimating divergence times rather than using the individual gene approach. (2) When sequence data from many nuclear genes are available, protein sequences appear to give more robust estimates than deoxyribonucleic acid (DNA) sequences. (3) Nuclear proteins are generally more suitable than mitochondrial proteins for time estimation. (4) It is important first to construct a phylogenetic tree for a group of species using some outgroups and then estimate the branch lengths. (5) It appears to be better to use a few reliable calibration points rather than many unreliable ones.