title: Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi.
abstract: In the past, molecular clocks have been used to estimate divergence times among animal phyla, but those time estimates have varied widely (1200-670 million years ago, Ma). In order to obtain time estimates that are more robust, we have analysed a larger number of genes for divergences among three well-represented animal phyla, and among plants, animals and fungi. The time estimate for the chordate-arthropod divergence, using 50 genes, is 993 +/- 46 Ma. Nematodes were found to have diverged from the lineage leading to arthropods and chordates at 1177 +/- 79 Ma. Phylogenetic analyses also show that a basal position of nematodes has strong support (p > 99%) and is not the result of rate biases. The three-way split (relationships unresolved) of plants, animals and fungi was estimated at 1576 +/- 88 Ma. By inference, the basal animal phyla (Porifera, Cnidaria, Ctenophora) diverged between about 1200-1500 Ma. This suggests that at least six animal phyla originated deep in the Precambrian, more than 400 million years earlier than their first appearance in the fossil record.
authors: Department of Biology, Pennsylvania State University, University Park 16802, USA.
authors: D Y
authors: DY
authors: Wang
authors: S
authors: S
authors: Kumar
authors: S B
authors: SB
authors: Hedges
mesh_terms: D000818:Animals; D001181:Arthropods; D005075:Biological Evolution; D002816:Chordata, Nonvertebrate; D005658:Fungi; D009348:Nematoda; D000069497:Origin of Life; D019151:Peptide Library; D010802:Phylogeny; D010944:Plants
chemical_list: D019151:Peptide Library