Quality of the fossil record through time

Does the fossil record present a true picture of the history of life(1-3), or should it be viewed with caution(4-6)? Raup(5) argued that plots of the diversification of life(2) were an illustration of bias: the older the rock s, the less we know. The debate was partially resolved by the observation(7 ) that different data sets gave similar patterns of rising diversity throug h time. Here we show that new assessment methods, in which the order of fos sils in the rocks (stratigraphy) is compared with the order inherent in evo lutionary trees (phylogeny), provide a more convincing analytical tool: str atigraphy and phylogeny offer independent data on history. Assessments of c ongruence between stratigraphy and phylogeny for a sample of 1,000 publishe d phylogenies show no evidence of diminution of quality backwards in time. Ancient rocks clearly preserve less information, on average, than more rece nt rocks. However, if scaled to the stratigraphic level of the stage and th e taxonomic level of the family, the past 540 million years of the fossil r ecord provide uniformly good documentation of the life of the past.